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Strain potentials of copper wire in potasium nitrate solutions Hoskins, Alfred Donald 1956

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STRAIN POTENTIALS OF COPPER WIRE IN POTASSIUM NITRATE SOLUTIONS  by A. DONALD HOSKDJS  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE IN CHEMICAL ENGINEERING i n the Department of Chemical Engineering  We accept t h i s thesis as conforming to the standard required from candidates f o r the degree of MASTER OF APPLIED SCIENCE.  Members of the Department of Chemical Engineering  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1956  i  ACK3ST0WLED GEMENT The  author i s s i n c e r e l y indebted  t o D r . L.W.  S h e m i l t f o r h i s g u i d a n c e and encouragement, t o D r . D.S. S c o t t f o r the l o a n o f t h e m e a s u r i n g equipment, and..to t h e National Research Council f o r t h e i r f i n a n c i a l assistance throughout the year.  R. Rye gave v e r y h e l p f u l a s s i s t a n c e i n  p r e p a r i n g t h e p h o t o g r a p h s and r e p r i n t s .  ABSTRACT The e f f e c t o f u n i - d i r e c t i o n a l s t r e s s on t h e e l e c t r o d e p o t e n t i a l o f copper i n a e r a t e d p o t a s s i u m s o l u t i o n s was s t u d i e d . temperature,  nitrate  The i n f l u e n c e o f t h e v a r i a b l e s t i m e ,  c o n c e n t r a t i o n , magnitude of s t r e s s , mechanic-  a l c o n d i t i o n o f t h e m e t a l , and pH was c o n s i d e r e d . -The p o t e n t i a l d i f f e r e n c e between two s i z e #22 B & S copper w i r e s was c o n t i n u o u s l y r e c o r d e d on a type G Speedomax a u t o m a t i c recorder.  A "balance p a n was a t t a c h e d t o one of t h e w i r e s  to w h i c h w e i g h t s were added and t h e change i n t h e p o t e n t i a l d i f f e r e n c e between t h e two w i r e s f r o m t h e p r e - s t r e s s p o t e n t i a l d i f f e r e n c e was t a k e n as t h e s t r a i n p o t e n t i a l .  At  l e a s t f o u r r u n s , u s i n g f r e s h p a i r s o f w i r e s f o r each r u n , were c a r r i e d o u t to i l l u s t r a t e  each s p e c i f i c p o i n t and t o  show t h e r e s u l t s have s t a t i s t i c a l reproducible.  s i g n i f i c a n c e and a r e  The f o l l o w i n g r e s u l t s were o b t a i n e d : (A) E l e c t r o n e g a t i v e s t r a i n p o t e n t i a l s have heen o b t a i n e d f o r copper m e t a l i n a e r ated potassium n i t r a t e s o l u t i o n ;  these  changes a c h i e v e a maximum a t t h e i n s t a n t o f s t r e s s i n g and then d e c a y w i t h a negative a c c e l e r a t i o n with time. A f t e r an i n i t i a l p e r i o d o f t i m e , t h e s t r a i n p o t e n t i a l decayed l o g a r i t h m i c a l l y w i t h t i m e . The magnitude of t h e e l e c t r o negative s t r a i n p o t e n t i a l f o r a given  s t r e s s i n c r e a s e d e x p o n e n t i a l l y w i t h the r e c i p r o c a l of the absolute  temperature  and remained e s s e n t i a l l y unchanged f o r c o n c e n t r a t i o n changes r a n g i n g f r o m 0.005H t o 0.500N. (B) E x p e r i m e n t a l support  e v i d e n c e was o b t a i n e d t o  the p o s t u l a t e that s t r a i n pot-  e n t i a l s of copper m e t a l i n a e r a t e d p o t assisan n i t r a t e s o l u t i o n and t h e i r time dependence p a r a l l e l f i l m r u p t u r e ;  the  e f f e c t o f the change i n i n t e r n a l  energy  due  to p l a s t i c d e f o r m a t i o n  ignored.  cannot be  TABLE 017 CONTENTS page Acknowledgement Abstract Table o f C o n t e n t s  i i i iv  L i s t of I l l u s t r a t i o n s  v  INTRODUCTION  1  PREVIOUS INVESTIGATIONS  4  THEORETICAL CONSIDERATIONS  20  APPARATUS AND PROCEDURE  35  EXPERIMENTAL RESULTS  43  DISCUSSION  53  BIBLIOGRAPHY  59  APPENDIX I  63  APPENDIX I I  87  V  L I S T OF ILLUSTRATION Figure 1. Test C e l l . .. 2. Arrangement o f Test C e l l s i n C o n s t a n t Temperature B a t h 3. Assemblage o f A p p a r a t u s 4. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S Hard Copper Wire i n 0.005N KETO3 a t 25.0° C 5. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.005N KNO3 a t 25.0° C 6. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.005H KNO3 a t 40.0° C 7. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.005N K N O 3 a t 60.0° C 8. Log (Max. S t r a i n P o t e n t i a l ) v e r s u s t h e R e c i p r o c a l o f t h e A b s o l u t e Temperature 9. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.05U KHO3 a t 25.0° C 10. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.05H K N O 3 a t 40.0° C 11. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.05K K N O 3 a t 60.0° C 12. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.5U KCTO3 a t 25.00 C ... 13. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper W i r e i n 0.5N KUO3 a t 40.0° C 14. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper W i r e i n 0.5H KUO3 a t 60.0° C 15. Log (Max. S t r a i n P o t e n t i a l ) v e r s u s t h e R e c i p r o c a l o f t h e A b s o l u t e Temperature 16. S t r a i n P o t e n t i a l - Time Curve f o r #22 B & S S o f t Copper Wire i n 0.05N CUSO4. 5HJ20 a t 25.0° C 17. S t r a i n P o t e n t i a l v e r s u s Log (Time)  Page 36 37 39 74 75 76 77 78 79 80 81 82 83 84 85 86 89  IHTRODUCTION  The c o r r o s i o n of m e t a l s has l o n g been a s e r i o u s p r o b l e m to t h e c h e m i s t , m e t a l l u r g i s t , and e n g i n e e r , b u t i n more r e c e n t y e a r s t h e a d d i t i o n a l e f f e c t o f s t r e s s e s o f a l l k i n d s has g r e a t l y i n c r e a s e d t h e i n t e r e s t o f the e n g i n e e r i n the m a t t e r .  The r e s e a r c h e r  has "been hampered i n h i s i n -  v e s t i g a t i o n s because o f t h e dependence o f c o r r o s i o n on a g r e a t number of v a r i a b l e s .  F o r example, one must  consider  the n a t u r e of the m e t a l ' s environment, t h e n a t u r e and i n t r i n s i c m i c r o s t r u c t u r a l p r o p e r t i e s o f t h e m e t a l and i t s s u r f a c e , the a b i l i t y of the m e t a l t o f o r m p r o t e c t i v e f i l m s , the amounts and d i f f u s i o n a l r a t e s o f oxygen and o t h e r  gases,  e x t e r n a l and i n t e r n a l s t r e s s e s o f t h e m e t a l and t h e i r r e s u l t a n t s t r a i n s , temperature, pressure,  and t i m e .  These  v a r i a b l e s a r e f u r t h e r oonfused by such f a c t o r s as whether s t r e s s e s a r e s t a t i c o r c y c l i c and b y the magnitude of s t r a i n .  and r a t e  U n t i l r e c e n t l y the r e l a t i o n s h i p between c o r r o s -  i o n and the v a r i a b l e s of e x t e r n a l and i n t e r n a l s t r e s s and  2  resultant  s t r a i n has l a r g e l y been n e g l e c t e d .  Investigators  o f s t r e s s c o r r o s i o n have f o u n d s e e m i n g l y d i f f e r e n t and conflicting results.  However, one fundamental f a c t o r o f grow-  i n g importance i n t h e s e r e s u l t s i s t h e r e l a t i o n s h i p o f s t r a i n and t h e r e s u l t i n g s t r a i n p o t e n t i a l t o s t r e s s - c o r r o s i o n . S t r a i n , either e l a s t i c or p l a s t i c  (inelastic),  accompanies t h e a p p l i c a t i o n o f s t r e s s t o a m e t a l body.  Strain  p o t e n t i a l s a r e d e f i n e d as t h e changes i n m e t a l e l e c t r o d e p o t e n t i a l w h i c h accompany t h e a p p l i c a t i o n o f s t r e s s t o a m e t a l i n an e l e c t r o l y t i c environment. i s preferred  The term s t r a i n p o t e n t i a l  to t h e term s t r e s s p o t e n t i a l s i n c e t h e r e a r e many  experimental i n d i c a t i o n s that  t h e change i n t h e e l e c t r o d e poten-  t i a l i s caused "by t h e r u p t u r e o f a p r o t e c t i v e  f i l m on t h e  s u r f a c e o f t h e m e t a l a s a r e s u l t o f t h e s t r a i n w h i c h accompan i e s the s t r e s s . This i n v e s t i g a t i o n represents a continuation work p r e v i o u s l y vestigators.  of the  c a r r i e d on a t t h i s " u n i v e r s i t y b y s e v e r a l i n The s t r a i n p o t e n t i a l s o f copper, b o t h c o l d  drawn and a n n e a l e d , i n a s o l u t i o n o f a e r a t e d p o t a s s i u m n i t r a t e have been measured.  The changes i n e l e c t r o d e p o t e n t i a l  were i n d u c e d b y e x t e r n a l u n i - d i r e c t i o n a l s t r e s s . Mniato  (23) and M c D o n n e l l  Previously,  (24) attempted t o r e l a t e t h e change  i n i n t e r n a l energy "caused b y d e f o r m a t i o h o f t h e m e t a l t o t h e change i n e l e c t r o d e p o t e n t i a l .  W M l e t h i s change u n d o u b t e d l y  3  has some e f f e c t on t h e e l e c t r o d e p o t e n t i a l , i t has been shown t h a t i t i s n o t t h e dominant f a c t o r .  D u d l e y (26) t h o r o u g h l y  e x p l o r e d t h e s t r a i n p o t e n t i a l s o f copper i n c u p r i c solution.  Elliott  sulfate  (27) c o n f i r m e d D u d l e y ' s and M c D o n n e l l ' s  work on copper i n c u p r i c s u l f a t e and extended t h e r e s e a r c h t o include  a s t u d y o f s t r a i n p o t e n t i a l s o f copper i n c u p r i c  ride solution.  chlo-  The r e s e a r c h r e p o r t e d h e r e extends f u r t h e r t h e  s t u d y o f s t r a i n p o t e n t i a l s o f copper i n e l e c t r o l y t i c s o l u t i o n s to p o t a s s i u m n i t r a t e and i n d i c a t e s t h a t s u r f a c e e f f e c t s a r e p a r t i c u l a r l y i m p o r t a n t i n any c o n s i d e r a t i o n metal electrode p o t e n t i a l w i t h external  o f t h e change o f  stress.  4  PREVIOUS INVESTIGATIONS I n t h e p a s t 60 y e a r s t h e r e has "been a l a r g e number of i n v e s t i g a t i o n s i n t o the e f f e c t o f s t r e s s on e l e c t r o d e p o t e n tials.  Pew  have "been e x t e n s i v e , and i n g e n e r a l , wherever  comparison has been p o s s i b l e , many s e e m i n g l y d i f f e r e n t and c o n f l i c t i n g r e s u l t s have "been r e p o r t e d .  Most o f the d i s c r e -  p a n c i e s r e s u l t f r o m the n e g l e c t o f i n v e s t i g a t o r s to the e f f e c t o f some one o r more o f the many i m p o r t a n t have on s t r e s s - c o r r o s i o n . a r i s e s due old  Another u n f o r t u n a t e  consider variables  difficulty  to l a c k o f s e c u r i n g r e p r o d u c i b l e c o n d i t i o n s .  i d e a t h a t the i n t r i n s i c  The  tendency of a m e t a l to i o n i z e  m a t e r i a l l y a s s i s t e d by s t r e s s , s t i l l  was  seemed t o be e v i d e n t i n  many r e p o r t s , d e s p i t e p r o o f t o the c o n t r a r y g i v e n by Walker and D i l l ( l ) as f a r back as The been e l o n g a t e d  1907.  e l e c t r o d e p o t e n t i a l of s t e e l b a r s , w h i c h had 20%  and p l a c e d i n sodium c h l o r i d e , were meas-  u r e d by Andrews ( 2 ) .  He f o u n d t h a t deformed s t e e l was  1 to  # 19 mv.  electronegative  t o o r d i n a r y s t e e l samples.  # The c o n v e n t i o n , as proposed by B a n c r o f t (3) and a c c e p t e d b y most European c h e m i s t s , t h e A m e r i c a n C h e m i c a l S o c i e t y , and t h e N a t i o n a l B u r e a u o f S t a n d a r d s (Wash.), i s used i n q u o t i n g the v a l u e o f the e l e c t r o d e p o t e n t i a l r e f e r r e d t o t h e hydrogen e l e c t r o d e datum; a n e g a t i v e e l e c t r o d e p o t e n t i a l change means a change to a more a n o d i c ( l e s s n o b l e ) e l e c trode p o t e n t i a l , i . e . , r e d u c t i o n p o t e n t i a l s are p o s i t i v e .  5  Hambuechen ( 4 ) . t e s t e d s t e e l , copper, b r a s s , z i n c ,  and  wrought i r o n by s t r e s s i n g samples up to the y i e l d p o i n t i n f e r r i c chloride solution.  I n a l l t e s t s the e l e c t r o d e  e n t i a l became more e l e c t r o n e g a t i v e ; o f 0.6  t o 29 mv.  changes were o f the  order  R i c h a r d s and Behr (5) and Walker and D i l l  s t u d i e d the i r o n e l e c t r o d e .  The f o r m e r r e p o r t e d  became c a t h o d i c when s u b j e c t e d elastic  pot-  (l)  that i r o n  to t e n s i l e s t r e s s w i t h i n  the  limit. Walker and D i l l c o n s i d e r e d  Andrew's and  work u n s a t i s f a c t o r y f r o m an e l e c t r o - c h e m i c a l t h e i r n e g l e c t o f time as a v a r i a b l e and l i n g samples.  Hambuechen's  viewpoint,  in  t h e i r method of hand-  They t e s t e d s t e e l samples, by m e a s u r i n g the  p o t e n t i a l p o t e n t i o m e t r i c a l l y w i t h a c a l o m e l c e l l as  reference,  d u r i n g the s t r e s s i n g o f the samples up to the b r e a k i n g i n ferrous sulfate solutions.  T h e i r r e s u l t s may  point,  be summa-  r i z e d as f o l l o w s : 1) The magnitude o f the p o t e n t i a l change s u f f e r e d by s o f t i r o n i n t e n s i o n b e l o w the e l a s t i c l i m i t exceedingly  s m a l l , 0.1  to 0.4  mv.,  but c o n s i d e r a b l y  was  larger -2  t h a n the v a l u e c a l c u l a t e d f r o m the maximum work, 1.34  x  10  mv., 2) s t r e s s e s above the e l a s t i c l i m i t caused p o t e n t i a l changes r e a c h i n g  50mv. w i t h the magnitude o f  i n c r e a s e depending upon the r a t e o f s t r a i n i n g , and a b r u p t l y when s t r a i n i n g c e a s e s ,  the  ceasing  6  3) t o r s i o n gave s i m i l a r r e s u l t s t o t e n s i o n , and 4) a f t e r b r e a k i n g , t h e p o t e n t i a l  returned  w i t h t i m e to a v a l u e s l i g h t l y e l e c t r o p o s i t i v e to t h e  initial  electrode potential. Walker and D i l l i n i t i a t e d the c o n s i d e r a t i o n o f s u r f a c e on s t r e s s c o r r o s i o n t h r o u g h t h e i r r e s u l t s above the  effects  elastic  l i m i t and by c l a i m i n g t h a t e f f e c t s o t h e r t h a n the i n c r e a s e d t e n d e n c y o f the m e t a l to i o n i z e t h r o u g h s t r e s s i n g , caused t h e e l e c t r o d e p o t e n t i a l changes. r e s u l t s t o W a l k e r and D i l l .  B u r g e s s (6)  obtained  similar  They were, t h a t t h e change i n  p o t e n t i a l , when g r e a t enough t o be measured (above t h e l i m i t ) , was  n e g a t i v e , and t h a t somewhere above t h e  elastic  elastic  l i m i t the p o t e n t i a l r i s e s s u d d e n l y s e v e r a l hundredths o f a v o l t . M e r i c a (7) made s i m i l a r measurement on c<_ - b r a s s , i n s o l u t i o n s o f copper and z i n c s a l t s .  Using a potentiometric  method and c a l o m e l h a l f - c e l l as r e f e r e n c e , he o b t a i n e d e l e c t r o n e g a t i v e p o t e n t i a l change of 0.2 mv. l i m i t and 1.0  mv.  at fracture.  a t the  an  elastic  B e f o r e t e s t i n g t h e samples,  he p o l i s h e d the s u r f a c e w i t h emery and t h e n etched w i t h n i t r i c acid.  A i r was  e x c l u d e d f r o m the c e l l by an o i l l a y e r .  A  r e c e n t r e p o r t by Hears (8) emphasizes the n e g l i g i b l e e f f e c t of s t r e s s on the p o t e n t i a l of b r a s s .  H i k i t i n (9), using unstres-  sed samples as r e f e r e n c e e l e c t r o d e s , p u r s u e d the same type i n v e s t i g a t i o n on copper, s i l v e r , and i r o n , i n 0.1 N  of  solutions  7  of t h e i r corresponding s a l t s .  I t was shown t o be u n n e c e s s a r y  to cover t h e s u r f a c e o f t h e e l e c t r o l y t e w i t h o i l .  The po-  t e n t i a l change i n c r e a s e d w i t h t h e speed o f t h e d e f o r m a t i o n . I n a l l t e s t s w i t h copper, t h e p o t e n t i a l became more e l e c t r o negative.  The maximum change b e i n g 7 mv., w i t h h a r d copper  showing a l a r g e r p o t e n t i a l change t h a n s o f t copper. stressed  When  b y c o n t i n u o u s t e n s i o n u n t i l r u p t u r e , t h e copper beca-  me a b r u p t l y more e l e c t r o n e g a t i v e  a t the i n s t a n t of rupture.  A f t e r r u p t u r e , t h e p o t e n t i a l r e t u r n e d toward t h e i n i t i a l  value  w i t h a negative acceleration, but f a i l e d to reach i t after ten hours..  I f t h e copper, deformed b y l o a d , was l e f t l o a d e d , t h e  e l e c t r o d e p o t e n t i a l , a f t e r t h e l i n e a r d i m e n s i o n s o f t h e sample had  ceased t o change, r e t u r n e d towards t h e i n i t i a l v a l u e w i t h  a negative acceleration.  The speed o f t h e decay o f t h e po-  t e n t i a l towards i t s i n i t i a l v a l u e was t h e same, whether t h e sample was l o a d e d o r u n l o a d e d .  D e f o r m a t i o n changed t h e p o t -  e n t i a l o f i r o n a maximum of 40 mv. e l e c t r o n e g a t i v e l y , changed t h e p o t e n t i a l o f s i l v e r a maximum o f 20 mv. positively.  N i k i t i n states  and electro-  t h a t p o t e n t i a l changes may be a t -  t r i b u t e d t o temperature changes, s i n c e b o t h copper and i r o n show n e g a t i v e p o t e n t i a l changes when deformed and have negat i v e c o e f f i c i e n t s o f e l e c t r o d e p o t e n t i a l , w h i l e s i l v e r shows p o s i t i v e p o t e n t i a l changes when deformed and has a p o s i t i v e c o e f f i c i e n t of electrode p o t e n t i a l . Guatam and J h a (10) a t t e m p t e d t o d e t e r m i n e t h e  8  e f f e c t of c o n c e n t r a t i o n d i f f e r e n c e i n the e l e c t r o l y t e on e l e c t r o d e p o t e n t i a l s o f copper.  Maximum changes i n the  pot-  e n t i a l d i f f e r e n c e between two w i r e s , when w e i g h t s were added to one, were 6.7 rav. and 2.4 sulfate solutions.  mv.  i n N/250 and N/25  The p o t e n t i a l d i f f e r e n c e was  cupric measured by  t h e use of a suspended c o i l m i r r o r t y p e g a l v a n o m e t e r .  They  v a r i e d t h e s i z e o f the w i r e t o i n c l u d e 22, 24, and 26 S.W.G. copper w i r e .  Contrary  to N i k i t i n t h e y f o u n d t h a t the  ed w i r e a l w a y s became more e l e c t r o p o s i t i v e , and  strain-  concluded  t h a t some work i s n e c e s s a r y to d e t a c h i o n s f r o m the m e t a l l i c s u r f a c e , and t h a t t h i s work i s g r e a t e r i n t h e case of s t r a i n e d w i r e t h a n the u n s t r a i n e d .  the  They a t t r i b u t e d the r e s -  u l t , t h a t the s t r a i n e d w i r e i s more e l e c t r o p o s i t i v e , t o mole c u l a r a g g r e g a t e s t h a t formed t h r o u g h s t r e s s on t h e of the m e t a l ,  and h i n d e r e d  surface  the. passage o f i o n s f r o m the m e t a l  to t h e s o l u t i o n . Endo and Kanazawa (11) c o n c l u d e f r o m e x p e r i m e n t s w i t h v a r i o u s l y p r e p a r e d samples o f i r o n , i n H f e r r o u s  sulfate,  t h a t t h e r o u g h e r the s u r f a c e the g r e a t e r t h e e l e c t r o d e ential.  pot-  They s t a t e t h a t t e n s i l e s t r e s s p r o d u c e s an a n o d i c  change i n e l e c t r o d e p o t e n t i a l , w h i l e t h e e f f e c t o f  slight  s t r a i n on a s i n g l e i r o n c r y s t a l produced a s l i g h t l y more c a t h o d i c change.  They c o n c l u d e , f r o m p o t e n t i a l t i m e  t h a t the s u r f a c e of t h e e l e c t r o d e was  p a r t i a l l y covered w i t h  an i n v i s i b l e f i l m of f e r r o u s h y d r o x i d e or f e r r i c whose e f f e c t c o u l d not be e v a l u a t e d  curves,  hydroxide,  or e l i m i n a t e d .  Evans  9  and Simnad (12,13) i n v e s t i g a t e d t h e changes i n t h e e l e c t r o d e p o t e n t i a l o f m i l d s t e e l , i n H/lO a e r a t e d p o t a s s i u m c h l o r i d e and a c i d s o l u t i o n s under a l t e r n a t i n g and s t a t i c  stresses.  Their i n v e s t i g a t i o n s of s t a t i c s t r e s s e s i n d i c a t e d t h a t i r o n becomes more e l e c t r o n e g a t i v e w i t h t e n s i l e s t r e s s , w h i l e comp r e s s i v e s t r e s s e s caused e l e c t r o p o s i t i v e e l e c t r o d e p o t e n t i a l changes.  They c o n c l u d e d t h a t c o r r o s i o n f o l l o w s and e l e c t r o -  c h e m i c a l c o u r s e , s i n c e e l e c t r i c c u r r e n t s f l o w i n g between d i s c r e t e a n o d i c and e a t h o d i c  a r e a s were c a p a b l e o f b e i n g  detect-  ed on n a t u r a l l y c o r r o d i n g  specimens, and t h e s e c u r r e n t s were  s t r o n g enough t o a c c o u n t f o r the c o r r o s i o n a c t u a l l y o b s e r v e d . I n t h i s way, t h e y c o n c l u d e d t h a t s u r f a c e e f f e c t s were o f cons i d e r a b l e importance i n n e u t r a l s o l u t i o n s , b u t t h a t changes produced b y s t r e s s w i t h i n the m e t a l were more i m p o r t a n t i n hydrochloric acid solutions.  G u i l o t t e (14) measured t h e p o t -  e n t i a l o f i r o n w i r e i n aqueous f e r r o u s s u l f a t e s o l u t i o n as a f u n c t i o n of t e n s i l e s t r e s s . changes i n the e a t h o d i c  He o b s e r v e d s t a b l e , r e v e r s i b l e  d i r e c t i o n , w h i c h were p r o p o r t i o n a l t o  the a p p l i e d s t r e s s (80 v./lO,000 l b / i n ) . 2  H i g h p u r i t y aluminum, w i t h c a r e f u l l y p r e p a r e d s u r f a c e s , was t e s t e d b y D r u e t and J a c q u e t (15) i n Z>% sodium c h l o r ide solution. negative  They showed t h a t c o l d - w o r k i n g  change o f 40 to 50 mv.  A report  caused an e l e c t r o -  (16) on German ac-  complishments i n s t r e s s - c o r r o s i o n s t u d i e s c o n c l u d e d "that, i n g e n e r a l , s t r e s s e s caused an e l e c t r o n e g a t i v e change o f e l e c t r o d e  10  potentials.  Thompson (17.) r e p o r t e d a t h o r o u g h i n v e s t i g a t i o n  of t h e e f f e c t o f s t r e s s on t h e e l e c t r o d e p o t e n t i a l o f aluminum i n d i s t i l l e d w a t e r , t a p w a t e r , s a l t s o l u t i o n s , and s e a w a t e r . He measured t h e p o t e n t i a l d i f f e r e n c e "between t h e a n o d i c and c a t h o d i c s u r f a c e s b y comparing t h e s u r f a c e under e x a m i n a t i o n w i t h a saturated calomel h a l f - c e l l .  To d e t e c t d i f f e r e n t i a l  e f f e c t s and t h e o x i d i z i n g p o t e n t i a l o f t h e s o l u t i o n , he measur e d , a t t h e same t i m e , t h e p o t e n t i a l changes i n a  microelectro-  de^of the same m e t a l and a p l a t i n i i a m m i c r o - e l e c t r o d e , r e s p e c t ively.  H i s r e s u l t s may h e summarized as f o l l o w s : 1) E x t e r n a l  f r e e energy change i n v o l v e d  s t r e s s does n o t a f f e c t t h e  i n the i o n i z a t i o n of a metal,  2) s t r e s s e s below the e l a s t i c  limit  have no e f f e c t on the s t a b l e o x i d e f i l m o f c o m m e r c i a l l y p u r e aluminum and produce no measurable change i n e l e c t r o d e p o t e n t ial , 3) s t r e s s e s  above t h e e l a s t i c l i m i t cause  momentary r u p t u r e o f t h e f i l m on s o f t aluminum specimens and coincident 460  i n f l e c t i o n s on p o t e n t i a l - t i m e  c u r v e s as l a r g e as  mv., t h e s e p o t e n t i a l changes b e i n g always a n o d i c , 4 ) m e c h a n i c a l l y hardened aluminum spec-  imens show no s i g n s o f r u p t u r e o f t h e i r s u r f a c e f i l m s u n t i l f r a c t u r e , a t w h i c h t i m e an a n o d i c change i n e l e c t r o d e p o t e n t i a l o f 120  mv. was o b s e r v e d , 5) sodium c h l o r i d e may cause o x i d e o r  h y d r o x i d e f i l m breakdown on z i n c and copper t h r o u g h complex  11  c h l o r i d e f o r m a t i o n , h u t no breakdown o f an aluminum o x i d e f i l m was  o b s e r v e d , and 6) no e l e c t r o d e p o t e n t i a l changes  accompanied e x t e r n a l  s t r e s s i n completely deasrated  solutions,  when s u r f a c e f i l m s were removed f r o m t h e aluminum specimens before  stressing. Z a r e t s k y (18 ) r e p o r t s t h e measurement o f changes  i n e l e c t r o d e p o t e n t i a l s o f magnesium, magnesium a l l o y s , aluminum, s t e e l , copper, and z i n c , i n s o l u t i o n s o f H/lO sodium c h l o r i d e , IT/30 h y d r o c h l o r i c  a c i d , 3U s u l f u r i c a c i d , 111 s u l f -  u r i c a c i d , and N/25 s u l f u r i c a c i d , r e s p e c t i v e l y .  Kb r e a s o n s  c o u l d be f o u n d f o r h i s random c h o i c e s o f e l e c t r o l y t e s .  He used  the work o f d e f o r m a t i o n as a b a s i s b y c a l c u l a t i n g t h e expected changes i n t h e s t o r e d p o t e n t i a l energy due t o d e f o r m a t i o n . The r e s u l t s o b t a i n e d b y Z a r e t s k y may be summarized as f o l l o w s : 1) The c a l c u l a t e d  change i n e l e c t r o d e  p o t e n t i a l w i t h d e f o r m a t i o n was shown t o be s e v e r a l  times  s m a l l e r t h a n t h e e x p e r i m e n t a l one, 2) t e n s i l e and compressive s t r a i n o f magnesium and o f t h e magnesium a l l o y s made t h e i r e l e c t r o d e p o t e n t i a l s 6 t o 17 mv. l e s s n o b l e  (anodic),  3) t h e r e s i d u a l . t e n s i l e s t r a i n p o n d i n g to a l o a d o f 90% u l t i m a t e  corres-  s t r e n g t h made t h e e l e c t r o d e  p o t e n t i a l of aluminum, z i n c , and copper, i n s u l f u r i c a c i d s o l u t i o n s , l e s s n o b l e b y about 35 mv.,  12  4) t h e d i f f e r e n c e between t h e p o t e n t i a l s of t h e s t r a i n e d and u n s t r a i n e d m e t a l s d i m i n i s h e d w i t h t i m e . Akimov ( 1 9 ) , a c c o r d i n g t o Z a r e t s k y , a s s e r t s t h a t the p o t e n t i a l i s made l e s s n o b l e p r i n c i p a l l y b y a d i m i n u t i o n i n t h e work i n v o l v e d i n t h e e x i t o f t h e ion-atom f r o m t h e strained metal. Dill  T h i s p r i n c i p l e was d i s p u t e d by Walker and  ( l ) and b y Thompson ( 1 7 ) .  A c c o r d i n g t o another  view,  the p o t e n t i a l i s made l e s s n o b l e b y t h e i n c r e a s e i n t h e accumulated  p o t e n t i a l energy due t o d e f o r m a t i o n .  Ivans (20)  shares t h i s v i e w , though he p o i n t s o u t t h e i m p o r t a n t f u n c t i o n o f the o x i d e f i l m i n t h e c o r r o s i o n b e h a v i o r o f s t r a i n e d m e t a l s . Z a r e t s k y , b y choosing t h e v i e w p o i n t supported b y Evans,as a b a s i s , c o n c l u d e s t h a t t h e change i n e l e c t r o d e p o t e n t i a l , due to d e f o r m a t i o n , must be l a r g e l y due t o t h e r u p t u r i n g o f t h e o x i d e f i l m , s i n c e i n a l l cases c i t e d ,  experi-  mental p o t e n t i a l s were s e v e r a l t i m e s l a r g e r t h a n t h e c a l c u l a t e d p o t e n t i a l s due t o p o t e n t i a l energy changes, w h i c h formed the b a s i s . G o l d and s i l v e r , w i t h c a r e f u l l y p r e p a r e d s u r f a c e s , were t e s t e d b y E r y x e l l and Kach'trieb (21) i n aqueous s o l u t i o n s of t h e i r c o r r e s p o n d i n g s a l t s . They found t h a t e l e c t r o d e p o t e n t i a l changes r a r e l y exceeded 2 mv. E r y x e l l and  ftachtrieb  The r e s u l t s o b t a i n e d b y  may b e summarized as f o l l o w s :  l ) Tension rendered  s i l v e r and g o l d  e a t h o d i c i n aqueous s o l u t i o n s of t h e i r own s a l t s , a v e r i f i c a t i o n of Nitkin (9),  13  2) c o m p r e s s i o n produced a n o d i c changes i n e l e c t r o d e p o t e n t i a l , 3) below the e l a s t i c l i m i t p o t e n t i a l s were r e v e r s i b l e and p r o p o r t i o n a l to the  these  applied  external stress, 4) i n a l l e x p e r i m e n t s , the e l e c t r o d e was  reference  of the same m e t a l as the t e s t specimen, whenever  p o s s i b l e f r o m the same s t o c k ;  the i d e a l s i t u a t i o n of  i n i t i a l p o t e n t i a l i n t h e r e s u l t i n g c e l l was  no  r a r e l y achieved,  the d i f f e r e n c e i n p o t e n t i a l of t h e e l e c t r o d e s u s u a l l y amounted t o s e v e r a l m i l l i v o l t s and  i n a few c a s e s t o as h i g h as 15  mv.,  and 5) the c o n d i t i o n o f the m e t a l l i c s u r f ace was  shown to be an i m p o r t a n t v a r i a b l e , a l t h o u g h s t u d i e s  c e r t a i n v a r i a b l e s w i t h i n the e l e c t r o l y t e f a i l e d t o r e v e a l  of  the  n a t u r e of the p o l a r i z a t i o n . R o s s and  Thomas (22) r e c e n t l y i n v e s t i g a t e d  the  e f f e c t of p r e v i o u s o v e r s t r a i n on the e l e c t r o d e p o t e n t i a l s of s t e e l samples.  C o n t r a r y to t h e r e s u l t s o f Evans and  Simnad  (12,13), t h e y f o u n d the s t r a i n e d samples t o be c a t h o d i c the u n s t r a i n e d  sample i n n e u t r a l s o l u t i o n s by as much as 90  a f t e r twelve hours.  mv.  They a t t r i b u t e d the v a r i a t i o n of r e s u l t s  to the f a c t t h a t o n l y the o u t e r o x i d e f i l m on the s t e e l exposed t o the s o l u t i o n and not did  to  the m e t a l i t s e l f .  W a l t e r and D i l l , Evans and Simnad, and  was  They, as  Thompson, o b s e r v e d  14  the o s c i l l a t o r y (saw-toothed) n a t u r e o f t h e f i l m f o r m a t i o n . The  r e s u l t s of a most i n t e n s i v e i n v e s t i g a t i o n o f  copper s t r a i n p o t e n t i a l s , a t t h i s u n i v e r s i t y , w i l l the d i s c u s s i o n  conclude  of the r e s u l t s of previous i n v e s t i g a t o r s .  M n i a t o ~(23) hung p a i r s o f w i r e s i n v a r i o u s s o l u t i o n s and added w e i g h t s t o one w i r e t o o b s e r v e t h e e f f e c t o f s t a t i c t e n s i l e s t r e s s on t h e e l e c t r o d e  potential.  A l l measurements  were made w i t h a moving c o i l galvanometer, c a l i b r a t e d i n microvolts.  H i s r e s u l t s may be summarized as f o l l o w s : 1) S t r e s s i n g o f h a r d and s o f t copper and  s t e e l w i r e s i n a s o l u t i o n of 4% sodium c h l o r i d e produced an electronegative  p o t e n t i a l change o f up t o 1.5 v . , 2) t h e e l e c t r o d e  p o t e n t i a l changes o f  b r a s s and copper a r e f a m i l a r t o e x t e n s i o m e t r i c changes i n t h e s e m a t e r i a l s "below t h e e l a s t i c 3) e l e c t r o d e guage c o l d drawn copper w i r e s ,  limit, p o t e n t i a l changes o f #24  i n c u p r i c c h l o r i d e , ammonium  c h l o r i d e , sodium c h l o r i d e p l u s h y d r o c h l o r i c  a c i d , and sodium  c h l o r i d e p l u s h y d r o x i d e , were too l a r g e t o be measured  with  e x i s t i n g equipment. H c D o n n e l l (24) s u b s t i t u t e d a n u l l b a l a n c i n g p o t e n t i o m e t e r f o r p o t e n t i a l measurements, i n o r d e r t o e l i m i n a t e t h e a p p r e c i a b l e p o l a r i z a t i o n caused b y passage o f c u r r e n t the g a l v a n o m e t e r .  through  D e s p i t e a l a r g e number o f t e s t s he was  u n a b l e to r e p r o d u c e M n i a t o ' s r e s u l t s .  15  M c D o n n e l l ' s work may be summarized as f o l l o w s : 1) D i r e c t i o n and m a g n i t u r e o f t h e p o t e n t i a l change, produced b y s t r a i n i n g copper, depend upon t h e e l e c t r o lyte, 2) s t r e s s d i d not a p p r e c i a b l y the e l e c t r o d e  influence  p o t e n t i a l o f copper, u n l e s s accompanied b y  p l a s t i c s t r a i n (elongation),  i n d i c a t i n g that surface  effeets  a r e most i m p o r t a n t , 3) s t r e s s e s b e l o w t h e e l a s t i c  limit  produced I n a p p r e c i a b l e s t r a i n p o t e n t i a l s , 4) s t r a i n p o t e n t i a l s d i m i n i s h e d w i t h from  time  t h e maximum v a l u e o b t a i n e d a t t h e i n s t a n t o f l o a d i n g ;  t h i s decay f o l l o w e d  a logarithmic  r e l a t i o n s h i p i n d i c a t i n g the  r e g r o w t h of a s u r f a c e f i l m , 5) e l e c t r o n e g a t i v e  s t r a i n potentials of the  o r d e r of 5 and lOmv. were o b t a i n e d f o r a n n e a l e d copper w i r e i n 0.025N and 0.0025IT "cupric s u l f a t e s o l u t i o n s ,  respectively,  6) s t r a i n p o t e n t i a l s f o r c o l d drawn copper w i r e i n c u p r i c s u l f a t e s o l u t i o n were much l e s s t h a n t h e c o r r e s p o n d i n g s t r a i n p o t e n t i a l s f o r a n n e a l e d copper w i r e , and 7) p o t e n t i a l changes, t h a t c o u l d be a t t r i b u t e d to s t r e s s i n g , d i d n o t o c c u r u n l e s s t h e copper w i r e had been exposed to the e l e c t r o l y t e f o r a s u f f i c i e n t time f o r a f i l m to form.  16  J a m i e s o n ( 2 5 ) attempted t o i n v e s t i g a t e s t r a i n p o t e n t i a l s i n an oxygen f r e e atmosphere.  One s u c c e s s f u l r u n  w i t h h a r d copper w i r e i n H/lO c u p r i c s u l f a t e s o l u t i o n and a n i t r o g e n atmosphere showed t h a t ho d e t e c t a b l e s t r a i n p o t e n t i a l e x i s t e d f o r s t r e s s e s up t o f r a c t u r e . D u d l e y (26) r e p e a t e d and c o n f i r m e d M c D o n n e l l ' s work, and "compared t h e v a r i a b l e s , t e m p e r a t u r e and c o n c e n t r a t i o n , f o r cupric sulfate solutions f u l l y .  He used a pdtenti©metric  method o f m e a s u r i n g t h e d i f f e r e n c e i n p o t e n t i a l between a p a i r of w i r e s hung i n a c o r r o s i o n  cell.  H i s r e s u l t s may be summa-  r i z e d as f o l l o w s : 1) For t h e same c o n d i t i o n s t e m p e r a t u r e , s o f t copper w i r e gave g r e a t e r  o f l o a d and  electronegative  s t r a i n p o t e n t i a l s t h a n h a r d copper w i r e , 2 ) no s i g n i f i c a n t d i f f e r e n c e s were f o u n d for  d e a r a t e d s o l u t i o n s , compared t o a e r a t e d  solutions,  3) a l l p o t e n t i a l changes f o r s o f t copper w i r e i n c u p r i c s u l f a t e s o l u t i o n were e l e c t r o n e g a t i v e .  An  average v a l u e of 4.75 mv. maximum s t r a i n p o t e n t i a l was obt a i n e d f o r s i z e #22 S.W.G-. copper w i r e i n 0.05N c u p r i c  sulfate,  4) n e g l i g i b l e s t r a i n p o t e n t i a l s were o b t a i n e d u n t i l the s t r e s s exceeded t h e e l a s t i c  limit,  5) t h e r a t e o f decay o f t h e s t r a i n p o t e n t i a l v a r i e d w i t h t h e s i z e o f t h e w i r e used i n t h e t e s t ;  17  s l o w e r r a t e s were o b t a i n e d f o r l a r g e r s i z e d w i r e s ,  the  pot-  e n t i a l change never r e a c h e d z e r o a f t e r d e c a y , 6) an i n d u c t i o n p e r i o d f o r t h e w i r e s i n t h e e l e c t r o l y t e i s n e c e s s a r y b e f o r e any p o t e n t i a l change i s obtained with the a p p l i c a t i o n of s t r e s s , 7 ) t h e magnitude o f t h e maximum s t r a i n p o t e n t i a l of copper w i r e v a r i e d f r o m 1 t o 8 mv., as t h e concent r a t i o n of t h e c u p r i c s u l f a t e s o l u t i o n e l e c t r o l y t e v a r i e d  from  0.500H t o 0.0005H, 8 ) sense and magnitude o f t h e s t r a i n p o t e n t i a l o f copper w i r e v a r i e d w i t h t h e n a t u r e o f t h e e l e c t r o l y t e as f o l l o w s : (a) 0.05U CuSC-4 - e l e c t r o n e g a t i v e change of 4 mv. max. (b) 0.05IT HgSC>4 - e l e c t r o n e g a t i v e change o f 1 1 . mv. max. ( c ) 0.05N CuOlg - e l e c t r o p o s i t i v e change o f 5.5 mv. max. (d) 0.70N U a C l - e l e c t r o n e g a t i v e change of 11.5 mv. max. (e) 1.0H NagSOi - e l e c t r o n e g a t i v e change o f 11 mv. max., and 9 ) t h e maximum s t r a i n p o t e n t i a l f o r s i z e #18 B & S copper w i r e i n 0.05N c u p r i c s u l f a t e s o l u t i o n v a r i e d f r o m 4 rav. a t 25° C. t o over 30 mv. a t 85° C. the l o g a r i t h m  A plot  showed  o f t h e maximum s t r a i n p o t e n t i a l t o be l i n e a r  w i t h the r e c i p r o c a l of t h e a b s o l u t e t e m p e r a t u r e . Elliott  (27) a l s o s t u d i e d  s t r e s s , and "concentration.  the v a r i a b l e s , temperature,  He r e p r o d u c e d some o f t h e work  18  done b y D u d l e y ( 2 6 ) i n c u p r i c s u l f a t e s o l u t i o n s , and measured the  s t r a i n p o t e n t i a l s o f # 2 2 B & S h a r d and s o f t copper w i r e i n  cupric chloride solutions.  S t r a i n p o t e n t i a l measurements  were made b o t h w i t h a p o t e n t i o m e t e r and a Leeds and H o r t h r u p automatic r e c o r d i n g  p o t e n t i o m e t e r (Speedbmax).  His results  may be summarized a s f o l l o w s : 1)  Hard copper w i r e i n 0 . 0 5 H r ; c u p r i c  a t e s o l u t i o n a t 2 5 ° 0 . produced an e l e c t r o n e g a t i v e  sulf-  s t r a i n pot-  e n t i a l o f magnitude 1 . 4 4 rav;., 2)  s o f t copper w i r e i n 0 . 0 5 N c u p r i c  a t e s o l u t i o n a t 2 5 ° C. and 6 5 ° C. produced  sulf-  electronegative  s t r a i n p o t e n t i a l s o f magnitude 5 . 7 7 mv. and 1 5 . 9 4 mv.,  respect-  ively, 3)  t h e r e s u l t s f o r s o f t copper w i r e above,  combined w i t h D u d l e y ' s , showed on a p l o t t h a t t h e l o g a r i t h m of the maximum s t r a i n p o t e n t i a l was l i n e a r w i t h t h e r e c i p r o c a l of t h e a b s o l u t e t e m p e r a t u r e , 4)  t h e maximum s t r a i n p o t e n t i a l s o f s o f t  copper w i r e i n 0 . 0 5 N c u p r i c c h l o r i d e a t were e l e c t r o p o s i t i v e o f magnitude mv., r e s p e c t i v e l y .  12.34,  25,  35,  14.72,  50  and  19.00  65°  and  C. 21.23  A p l o t o f t h e s e r e s u l t s showed t h e l o g a -  r i t h m o f t h e maximum s t r a i n p o t e n t i a l t o b e l i n e a r w i t h t h e r e c i p r o c a l of the absolute temperature, 5)  the s t r a i n p o t e n t i a l s o f s o f t copper  w i r e i n s o l u t i o n s o f c u p r i c c h l o r i d e were e l e c t r o p o s i t i v e , a s a r e s u l t of the d e p o s i t i o n  of insoluble CuCl,  19  6) a n i n d u c t i o n p e r i o d was u n n e c e s s a r y i n 0.05W c u p r i c c h l o r i d e , t h e time f o r t h e maximum s t r a i n i a l t o decay to one-half  potent-  i t s maximum v a l u e i n c r e a s e d w i t h t h e  l e n g t h of the i n d u c t i o n p e r i o d , 7) no d i f f e r e n c e i n t h e maximum s t r a i n p o t e n t i a l r e s u l t e d , when t h e w e i g h t s p r o v i d i n g t h e s t a t i c s t r e s s were added s u c c e s s i v e l y , as opposed t o t o t a l l y .  20  THEORETICAL In considering  CONSIDERATIONS  t h e i n f l u e n c e o f s t r e s s upon t h e  electrode p o t e n t i a l of metals, i t i s d e s i r a b l e to begin w i t h a b r i e f d i s c u s s i o n o f t h e n a t u r e o f s t r e s s and a d e s c r i p t i o n o f t h e e f f e c t s o f s t r e s s upon t h e i n t e r n a l and e x t e r n a l structure of the metal.  I n t u r n , t h e e f f e c t s o f i n t e r n a l and  e x t e r n a l s t r e s s e s on t h e mechahisms t h a t e s t a b l i s h arid m a i n t a i n t h e p o t e n t i a l o f a m e t a l c o n t a c t i n g an e l e c t r o l y t e w i l l be discussed. S t r e s s may be d e f i n e d  as t h e i n t e n s i t y o f f o r c e  r e a c t i o n s t h a t a r e s e t up w i t h i n a body on a p p l i c a t i o n o f ext e r n a l l o a d s , o r b y n o n - u n i f o r m d i l a t i o n o f t h e body.  Strain  i s t h e change i n d i m e n s i o n s t h a t accompanies t h e development of s t r e s s e s , i t may be e l a s t i c o r p l a s t i c ,  (i.e., i t s t i l l  e x i s t s a f t e r t h e s t r e s s has been r e l i e v e d , l e a v i n g permanent deformation. When a m e t a l i s s u b j e c t e d  t o an e x t e r n a l l o a d , as b y  c o l d w o r k i n g , t h e d e f o r m a t i o n o r f l o w b e h a v i o r can be c h a r a c t e r i z e d b y the f a m i l i a r s t r e s s - s t r a i n diagram. p o r t i o n of the curve represents i s proportional to s t r e s s .  e l a s t i c d e f o r m a t i o n , where  However, above t h e e l a s t i c  t h i s p r o p o r t i o n a l i t y no l o n g e r has t a k e n p l a c e .  The l i n e a r strain  limit,  e x i s t s , and p l a s t i c d e f o r m a t i o n  The e l a s t i c l i m i t i s n o t a w e l l  defined  21  p h y s i c a l c o n s t a n t , and o f t e n i t i s more d i f f i c u l t t o d e t e r m i n e t h e e x a c t s t r e s s v a l u e f o r p l a s t i c d e f o r m a t i o n , even i n a s i m p l e tension test. stress-strain  McKeown and Hudson (28) have measured t h e characteristics  o f copper, s i l v e r , and g o l d and  found t h a t copper, l i k e t h e l a t t e r m e t a l s , has no  clearly  d e f i n e d e l a s t i c l i m i t i n the f u l l y - a n n e a l e d c o n d i t i o n . results  Their  show t h a t s t r e s s and s t r a i n a r e n o t c o m p l e t e l y p r o -  p o r t i o n a l f o r copper, even i n t h e e l a s t i c p o r t i o n o f t h e c u r v e . I t t h e r e f o r e seems c o n c e i v a b l e t h a t p l a s t i c d e f o r m a t i o n o c c u r s on a m i c r o s c o p i c s c a l e a t l o c a l i z e d v e r y s m a l l magnitude  s i t e s , under s t r e s s e s o f  (28,29).  When a m e t a l i s deformed i n t e r n a l the m e t a l .  changes o c c u r i n  I t i s o b v i o u s t h a t work i s b e i n g done on the  m e t a l system, much of w h i c h i s d i s s i p a t e d i n t h e f o r m o f h e a t . However a s i g n i f i c a n t f r a c t i o n o f t h i s work (50,31), r a n g i n g f r o m 5 t o 15$ i s s t o r e d up b y the m e t a l as l a t e n t w h i c h s e r v e s t o i n c r e a s e the i n t e r n a l system.  energy l e v e l o f t h e  I t i s this increase i n internal  energy,  f r o m the s t r a i n h a r d e n i n g o p e r a t i o n , t o w h i c h i s the c h a r a c t e r i s t i c  energy,  changes i n t h e p h y s i c a l and  resulting attributed  chemical  b e h a v i o r o f s t r e s s e d m e t a l s as compared t o u n s t r e s s e d m e t a l s . The a r e a under the s t r e s s - s t r a i n  c u r v e f o r any v a l u e o f s t r e s s  and s t r a i n r e p r e s e n t s the t o t a l amount o f energy i n t r o d u c e d i n t o t h e m e t a l d u r i n g the d e f o r m a t i o n o p e r a t i o n , arid has been  22  shown to he as l a r g e as 15 c a l o r i e s p e r gram ( 3 0 ) . w i r e under a t e n s i l e s t r e s s o f 10 c a l o r i e s p e r gram.  copper  dynes/this i s approximately cm  0.2  For  2  P l a s t i c d e f o r m a t i o n i s g e n e r a l l y ac-  companied b y an i n c r e a s e i n s t r e n g t h p r o p e r t i e s , and decrease i n d u c t i l i t y p r o p e r t i e s .  a  I n a d d i t i o n to these pro-  p e r t y changes, a t o m i c , c r y s t a l l o g r a p h i c and m i c r o s t r u c t u r a l changes may  o c c u r , as a r e s u l t o f d e f o r m a t i o n .  The p r o c e s s o f  p l a s t i c d e f o r m a t i o n i n v o l v e s such d i s t u r b a n c e s as  slip,  t w i n n i n g , w a r p i n g o f c r y s t a l p l a n e s , r o t a t i o n and e l o n g a t i o n of  g r a i n s , o r i e n t a t i o n e f f e c t , and a g e n e r a l breakdown o f t h e  crystal structure into a highly disorganized state.  The  e x t e n t t o w h i c h any o f t h e s e o p e r a t i o n s o c c u r s i s dependent upon the magnitude o f t h e s t r a i n , t h e s t r a i n r a t e , g r a i n o r i e n t a t i o n , and t h e temperature a t w h i c h t h e d e f o r m a t i o n occurs (32).  As a consequence, p l a s t i c d e f o r m a t i o n i s essen-  t i a l l y a non-homogeneous o p e r a t i o n , n o t o n l y f r o m a m i c r o s c o p i c p o i n t of v i e w , but" on a m a c r o s c o p i c  s c a l e as w e l l .  As i n d i c a t e d e a r l i e r , p l a s t i c d e f o r m a t i o n o f m e t a l s tends to i n c r e a s e t h e i r i n t e r n a l energy, and t h i s i n c r e a s e s h o u l d m a n i f e s t i t s e l f i n a g r e a t e r f r e e energy change. i s to b e expected f r o m the f o l l o w i n g r e l a t i o n s h i p  proposed  •by Gibbs ( 3 3 ) : = where  -nfE  F » t h e change i n the f r e e energy o f t h e f - Faraday constant  This  (1.) system  23  n * number of e l e c t r o n s i n v o l v e d E «• e l e c t r o d e p o t e n t i a l E q u a t i o n (l-) may be a p p l i e d o n l y t o r e v e r s i b l e systems and hence cannot be m o d i f i e d t o a p p l y t o any r e a c t i o n i n v o l v i n g p l a s t i c deformation (32).  That t h e change i n e l e c -  t r o d e p o t e n t i a l w i l l o c c u r , due to d e f o r m a t i o n , i s c e r t a i n , b u t i t s magnitude cannot be c a l c u l a t e d f r o m any s i m p l e thermodynamic r e l a t i o n s h i p .  Thus, a t h e o r e t i c a l e x p l a n a t i o n o f  changes i n e l e c t r o d e p o t e n t i a l must cover t h e n a t u r e o f t h e p r o c e s s f o r m i n g t h e e l e c t r o l y t i c c e l l , t h e degree o f r e v e r s i bility  (or i r r e v e r s i b i l i t y ) , and t h e e f f e c t o f s t r e s s on  these processes.  The f i r s t and second elements  above w i l l  c o n s i d e r e d , f o l l o w e d by a c o n s i d e r a t i o n of the t h i r d  be  element;  emphasis w i l l be p l a c e d wherever p o s s i b l e on t h e d i r e c t a p p l i c a t i o n to copper  metal.  From a s t u d y o f the i n f l u e n c e o f boundary f i l m s  on  c o r r o s i v e a c t i o n C a l l e n d a r (34) c o n c l u d e d t h a t t h e e l e c t r o d e p o t e n t i a l , due to t h e p r e s e n c e o f o x i d e f i l m s , w i l l n o t  be  i d e n t i c a l throughout t h e s u r f a c e o f a m e t a l , and t h a t t h e o r i g i n a l l o c a t i o n o f anode and cathode a r e a s i s l i k e l y t o be a l t e r e d b y the d i s t r i b u t i o n of oxygen w i t h i n the s o l u t i o n . Langmuir ( 3 5 ) , f r o m h i s s t u d i e s on p a s s i v i t y and a n o d i c p o l a r i z a t i o n , p r e s e n t e d f u r t h e r e v i d e n c e t o show t h a t t h e s o l u t i o n - m e t a l i n t e r f a c e cannot be t r e a t e d , i n t h e most g e n e r a l case:,- as a s i n g l e homogeneous f i e l d , b u t must be thought o f  24  as a group of s u c h f i e l d s .  G-atty and  Spooner ( 3 6 ) , s t a t e  t h a t each f i e l d w i l l have a s e p a r a t e i n t e r f a c i a l difference due  of i t s own,  and  further  potential  s i n c e i n g e n e r a l , t h e s e w i l l go  to the f l o w of " l o c a l - a c t i o n c u r r e n t s " .  on  At each f i e l d  whole v a r i e t y of e l e c t r o d e p o t e n t i a l s are p o s s i b l e ,  and  a  for  a  s t e a d y p o t e n t i a l i t i s not n e c e s s a r y t h a t n e t f l o w over a l l t h e s u r f a c e p a t c h e s of one  f i e l d or a n o t h e r s h o u l d be  zero;  i t is  the net f l o w of c u r r e n t a c r o s s the whole i n t e r f a c e t h a t must become z e r o i n the s t e a d y s t a t e , as opposed to a t r u l y r e v e r s i b l e system.  B a n n i s t e r and Evans (37) d i s c u s s e d q u a l i t a t i v e l y  the r e l a t i o n s h i p s between the and  e l e c t r o d e p o t e n t i a l of the m e t a l  a p a r t l y or c o m p l e t e l y o x i d e c o a t e d m e t a l . H e a r s and Brown (38) have o u t l i n e d  o f l o c a l - a c t i o n c u r r e n t s and ential fields.  The  e i g h t e e n causes  t h e i r r e s u l t a n t d i f f e r e n t pot-  causes o f d i f f e r e n t p o t e n t i a l f i e l d s may  s e p a r a t e d i n t o groups a c c o r d i n g to t h e i r r e l a t i o n s h i p t o m e t a l , the m e t a l ' s s u r f a c e and  the  the m e t a l ' s environment as  follows s l ) Potential differences the m e t a l i n c l u d e d  differences  i m p u r i t i e s ) , d i s t o r t i o n s and  associated with  i n c o m p o s i t i o n (presence o f  d e f e c t s at g r a i n boundaries  r e l a t i v e to the g r a i n body, r e l a t i v e o r i e n t a t i o n of g r a i n s , and  adjacent  d i f f e r e n t i a l t h e r m a l or m e t a l l u r i g i c a l t r e a t m e n t .  They measured, w i t h the a i d of a f i n e t u b u l u s a t t a c h e d to 0.1$  a  c a l o m e l h a l f - c e l l , the p o t e n t i a l d i f f e r e n c e between t h e  "be  25  g r a i n boundary and the g r a i n body; c o n s e r v a t i v e r e s u l t s showed p o t e n t i a l d i f f e r e n c e s as h i g h as 15G mv.  f o r an alum-  inum a l l o y (96 - 4, A l - Cu) i n sodium c h l o r i d e .  I n a l l cases  the g r a i n boundary was more a n o d i c t h a n the body.  They f o u n d  s i m i l a r r e s u l t s between d i f f e r e n t c o n t i n u o u s  s o l i d phases i n  m e t a l l i c a l l o y s ; i n t h i s c a s e , however, t h e d i r e c t i o n o f t h e e l e c t r o d e p o t e n t i a l depended upon the s m a l l amounts o f m e t a l i n s o l i d s o l u t i o n w i t h the m a t r i x , and t h e  electrolytic  environment. Considerable experimental evidence  (11,39),  although  sometimes c o n f l i c t i n g , has i l l u s t r a t e d the e f f e c t o f g r a i n o r i e n t a t i o n on e l e c t r o d e p o t e n t i a l s , f o r example, M o r i z e  (39)  has r e c e n t l y shown the ( i l l ) f a c e s o f a s i n g l e c r y s t a l o f aluminum i s about 50 mv.  e l e c t r o p o s i t i v e i n m i l d a c i d to the  (001) f a c e , and W a l t o n ( 3 9 ) , a l s o w o r k i n g w i t h aluminum, f o u n d the same r e s u l t as M o r i z e b u t o f lower magnitude.  I n t h i s oase,  the s o l u t i o n p o t e n t i a l s were measured i n c o n c e n t r a t e d  hydro-  chloric acid. 2) P o t e n t i a l d i f f e r e n c e s a s s o c i a t e d w i t h the metal  s u r f a c e i n c l u d e d i s c o n t i n u i t i e s of s u r f a c e f i l m s at  a n g u l a r p r o j e c t i o n s , s c r a t c h e s and a b r a s i o n s , c u t edges, convex and concave s u r f a c e s t h a t have d i f f e r e n t hydrogen o v e r v o l t a g e s , and d i f f e r e n t i a l p r e - e x p o s u r e d u r i n g f i l m f o r m a t i o n . and Brown l i s t r e f e r e n c e s f o r e x p e r i m e n t a l e v i d e n c e the above p o s s i b i l i t i e s .  Hears supporting  Hears (40) e s t a b l i s h e d t h a t w i r e s  26  of s m a l l e r d i a m e t e r  c o r r o d e more r a p i d l y t h a n w i r e s o f l a r g e  diameter. 3) P o t e n t i a l d i f f e r e n c e s a s s o c i a t e d w i t h t h e environment i n c l u d e d i f f e r e n t i a l c o n c e n t r a t i o n , d i f ferential aeration, differential s t i r r i n g with resulting differential polarization, differential illumination, different i a l h e a t i n g , and c o n t a c t w i t h o t h e r m e t a l s .  In  experiments  on d i f f e r e n t i a l a g i t a t i o n , ICears and Brown found t h a t copper was  a n o d i c "by as much as 40 mv.,  w h i l e s t e e l and aluminum  were o a t h o d i c "by as much as 10 and 80 mv., experiments were conducted  respectively.  under an a i r atmosphere.  The  They  a l s o l i s t e x p e r i m e n t a l e v i d e n c e and r e f e r e n c e s s u p p o r t i n g the above p o s s i b i l i t i e s . The observed p o t e n t i a l o f a m e t a l e l e c t r o d e , w i t h f i e l d s (or p a t c h e s ) of v e r y s m a l l d i m e n s i o n s  on the i n t e r f a c e ,  s h o u l d be the mean v a l u e f o r a l l the s e p a r a t e f i e l d s p o t e n t i a l s w e i g h t e d a c c o r d i n g t o t h e i r r e s p e c t i v e v a l u e s ( 3 6 ) . These a c t u a l p o t e n t i a l s do not c o r r e s p o n d  to s t e a d y p o t e n t i a l s f o r  the f i e l d i n q u e s t i o n because the c o n d i t i o n f o r a s t e a d y p o t e n t i a l a l l o w s l o c a l - a c t i o n c u r r e n t s to f l o w .  The non-zero  v a l u e s f o r the p o l a r i z a t i o n c u r r e n t s a c r o s s i n d i v i d u a l f i e l d s a l t e r the a c t u a l p o t e n t i a l a c r o s s them, o f t e n by c o n s i d e r a b l e b u t d i f f e r i n g amounts.  I f , t h e r e f o r e , an i n t e r f a c e has a l l  i t s f i e l d s d i v i d e d i n t o s u i t a b l y s m a l l p a t c h e s and the  total  a r e a of one f i e l d becomes g r e a t by comparison w i t h t h e sum  of  27  the toital areas of a l l remaining  f i e l d s , t h e n the observed p o t -  e n t i a l w i l l c o r r e s p o n d , to a f i r s t a p p r o x i m a t i o n , e n t i a l o f the p r e d o m i n a t i n g f i e l d . approximation  to a p o t -  T h i s must o n l y be a f i r s t  s i n c e the a c t u a l p o t e n t i a l of the p r e d o m i n a t i n g  f i i s l d i s s h i f t e d s l i g h t l y by p o l a r i z a t i o n a r i s i n g f r o m l o c a l a c t i o n c u r r e n t s ( s e l f - p o l a r i z a t i o n ) . T h i s p o l a r i z a t i o n const i t u t e s the n o n - r e v e r s i b i l i t i e s i n the g a l v a n i c c e l l s . of the causes of t h i s p o l a r i z a t i o n may  be p l a s t i c  deformation  (29) w h i c h a f f e c t s the p r o p e r t i e s of o x i d e s and o t h e r films.  P o l a r i z a t i o n o f anodes moves t h e e l e c t r o d e  One  surface  potential  to a more c a t h o d i c v a l u e w h i l e p o l a r i z a t i o n o f cathodes moves the e l e c t r o d e p o t e n t i a l to a more a n o d i c v a l u e .  The  above  q u a l i t a t i v e d i s c u s s i o n shows t h a t t h e o b s e r v e d p o t e n t i a l of  an  e l e c t r o d e depends upon the r e l a t i v e a r e a s o f the d i f f e r e n t s u r f a c e f i e l d s and upon the degree o f s e l f - p o l a r i z a t i o n e x i s tent thereon.  A d i s c u s s i o n of the s u r f a c e n a t u r e of copper  i s desired. Newberry (41) d e t e r m i n e d the s i n g l e p o t e n t i a l  of  the copper e l e c t r o d e and c o n c l u d e d t h a t f i l m s , even i f o n l y a monomolecular l a y e r , formed on the s u r f a c e of the copper e l e c t r o d e w i l l g r e a t l y a f f e c t the e l e c t r o d e p o t e n t i a l .  He  c r i t i c i z e d o t h e r w o r k e r s f o r i g n o r i n g the p r e s e n c e of hydrogen i n the m e t a l s u r f a c e , the use of a c i d s i n the  electro-  l y t e , and the methods of s u r f a c e p r e p a r a t i o n ; and noted t h a t n e a r l y a l l o t h e r w o r k e r s had a s c r i b e d t h e v a r i a t i o n s i n meas-  28  u r e d s i n g l e p o t e n t i a l s o f copper t o v a r i a t i o n s i n t h e n a t u r e of t h e s u r f a c e .  Many i n v e s t i g a t o r s  (42) have demonstrated  t h a t t h e f i l m formed on the s u r f a c e o f copper i n a i r i s p r i n c i p a l l y cuprous o x i d e .  The n a t u r e o f the o x i d e f i l m was  s t u d i e d u s i n g e l e c t r o n d i f f r a c t i o n , p o l a r i m e t r i c , and e l e c t r i c a l methods w i t h no a p p r e c i a b l y d i f f e r e n t r e s u l t . McCandles, and E h i n e s  Mehl,  (42) found t h a t t h e axes o f t h e c u p r o u s  o x i d e and copper m e t a l c r y s t a l s l a y a c c u r a t e l y p a r a l l e l when the o x i d e was grown on a s i n g l e . c r y s t a l I n a i r .  The copper  atoms formed a f a c e c e n t e r e d c u b i c l a t t i c e i n t h e o x i d e , w h i l e the oxygen atoms formed an i n t e r p e n e t r a t i n g body c e n t e r e d cubic.  T h i s d e f i n i t e c r y s t a l p a t t e r n , a d j a c e n t to t h e m e t a l  i t s e l f , soon d i s a p p e a r e d and a random s t r u c t u r e r e s u l t e d as oxidation continued.  Hence, i n t h e b e g i n n i n g , t h e o x i d e f i l m  i s formed m e r e l y b y e x t e n s i o n o f the m e t a l l a t t i c e ; conseq u e n t l y , b r e a k s i n t h e f i l m s h o u l d ensue a t g r a i n b o u n d a r i e s and o t h e r i r r e g u l a r i t i e s .  P r e s t o n and B i r k e n s h a w (42) showed  t h e ( i l l ) f a c e s to have a marked t h i c k e n i n g , w h i c h  suggests  the e x i s t e n c e o f some p r e f e r r e d growth o r i e n t a t i o n w i t h t h e ( i l l ) plane.  "Wilkins (43) e s t a b l i s h e d a mechanism f o r t h e  o x i d e f o r m a t i o n , w h i c h occured i n t h r e e c o n s e c u t i v e s t a g e s as follows: a) Condensation  o f oxygen a t t h e oxide/oxygen  interface, b ) e v a p o r a t i o n of oxygen i n t o t h e o x i d e , and  c ) d i f f u s i o n o f oxygen t h r o u g h t h e o x i d e t o t h e  s u r f a c e o f t h e copper.  29 Evans and M i l e y (42) found t h e o x i d e formed v e r y r a p i d l y t o a t h i c k n e s s of about 90 angstroms -within a f e w m i n u t e s a t 18° C , t h e n t h i c k e n e d no more t h a n f i v e angstrom u n i t s throughout  a p e r i o d of several hours. Mathematical r e l a t i o n s h i p s governing the r a t e  o f growth o f cuprous o x i d e on copper have b e e n p r o p o s e d b y P i l l i n g and Bedworth ( 4 2 ) , Tamman and K b s t e r ( 4 4 ) , Lustman ( 4 5 ) , Evans ( 4 6 ) , and D I g h t o n and M i l e y ( 4 7 ) . A t h i g h t e m p e r a t u r e s , P i l l i n g and Bedworth (42) and D i g h t o n and M i l e y (47 ) found t h e r a t e o f growth governed b y a p a r a b o l i c r e l a t i o n s h i p o f the form y where  2  »  y  - f i l m thickness  t  -  at+b  (2.)  time  a,b =- c o n s t a n t s ,  Lustman (45 ) and Evans (46) f o u n d t h i s l a w to b e f o l l o w e d c l o s e l y once t h e f i l m was e s t a b l i s h e d , b u t to f a i l a t t h e b e g i n n i n g o f f i l m f o r m a t i o n .  This f a c t can  be r e a d i l y e s t a b l i s h e d m a t h e m a t i c a l l y s i n c e t h e r a t e of f i l m growth w i t h r e s p e c t t o time would have t o be i n f i M t e i n i t i a l l y i n o r d e r to s a t i s f y a p a r a b o l i c r e l a t i o n s h i p , t h a t i s , i n f i n i t e a t zero t i m e . , w o r k i n g a t o r d i n a r y temperatures  Tamman and K o s t e r (44) proposed  the f o l l o w i n g  r e l a t i o n s h i p f o r cuprous o x i d e g r o w t h : t where  t  =  ©  — film  a,h -  =, ae « b  (3.)  time thickness  constants.  Wagner (48) suggested t h a t the p a r a b o l i c l a w was v a l i d , a t h i g h t e m p e r a t u r e s , because d i f f u s i o n o f oxygen t o t h e m e t a l s u r f a c e t h r o u g h a f a i r l y t h i c k f i l m c o n t r o l l e d t h e growth.  He a l s o suggested t h a t a t o r d i n a r y  t e m p e r a t u r e s on r a t h e r t h i n f i l m s , t h a t i r r e v e r s i b l e change of t h e m e t a l l i c o x i d e l a y e r caused a l o g a r i t h m i c l a w t o be v a l i d . D i g h t o n and M i l e y ' (47) e s t a b l i s h e d b y experi m e n t a l e v i d e n c e t h a t n o t o n l y t h e p a r a b o l i c l a w menti o n e d above as e q u a t i o n ( 2 . ) was v a l i d b u t t h a t t h e growth r a t e c o u l d under c e r t a i n c i r c u m s t a n c e s t a k e t h e form o f a l i n e a r or logarithmic r e l a t i o n s h i p .  They c o n c l u d e d t h a t  the growth r a t e r e l a t i o n s h i p c o u l d b e g i n l i n e a r , be t r a n s formed t o a p a r a b o l i c r e l a t i o n s h i p , and f i n a l l y , be t r a n s formed t o a l o g a r i t h m i c r e l a t i o n s h i p , as d i f f e r e n t mechanisms became r a t e c o n t r o l l i n g . The l i n e a r r e l a t i o n s h i p would t a k e t h e f o r m y  -  at + b  (4.)  31  w h i l e the l o g a r i t h m i c r e l a t i o n s h i p could take e i t h e r of the f o r m s ; y  ^  k l o g ( a t + C)  (5. )  y =.  k loga(t+tVl/a)  (6.)  y =  film  or  where  thickness  t  x.  \f  =• c o n s t a n t zero time e r r o r  a,c —  time  constants.  They c o n c l u d e d t h a t l i n e a r growth r a t e  v: r e s u l t -  ed when t h e mechanics o f t h e f i l m b u i l d i n g p r o c e s s c o n t r o l l e d t h e growth w h i l e t h e l o g a r i t h m i c growth r a t e r e s u l t e d when growth r a t e became l e s s t h a n t h a t o f t h e p a r a b o l i c l a w due to the a c t i o n of p o l a r i z a t i o n . extensive  They p r o v i d e d ,  a r t i c l e , an e l e c t r o c h e m i c a l  i n their  i n t e r p r e t a t i o n of  the i o n i c t h e o r y as a b a s i s f o r d e v e l o p i n g t h e e q u a t i o n s o f t h e l i n e a r , p a r a b o l i c , and l o g a r i t h m i c  laws.  Bengough and May ( 4 9 ) , Evans (50,51), Haase ( 5 2 ) , and  Campbell and Thomas ( 5 3 ) showed t h a t a cuprous o x i d e f i l m  was, i n g e n e r a l , formed i n aqueous s o l u t i o n s , and t h a t , i f t h i s f i l m i s s t a b l e , i t e x h i b i t s i n h i b i t i v e p r o p e r t i e s , and  32  r e t a r d s the r a t e o f m e t a l d i s s o l u t i o n .  I t then f o l l o w s that  a t the moment o f immersion of a copper e l e c t r o d e i n aqueous aerated  s o l u t i o n , t h e e l e c t r o d e s u r f a c e i s covered w i t h a f i l m  o f cuprous o x i d e and i s d i v i d e d i n t o anodes a t f i l m d i s c o n t i n u i t i e s and  i n t o c a t h o d e s a t the c o n t i n u o u s o x i d e  film.  I v a n s (54) showed t h a t the r a t e of o x i d e growth v a r i e d w i t h crystal orientation.  Hence, i f the f i l m happened t o "be con-  tinuous, i t undoubtedly w i l l vary i n t h i c k n e s s . anodes might e x i s t where t h e f i l m i s t h i n n e s t and where t h e f i l m i s t h i c k e s t .  Consequently, cathodes  M a t h e m a t i c a l developments f o r  t h i s would p r o b a b l y i n v o l v e c o n s i d e r a t i o n o f the Wagner Theory of Oxidation  (48, 55, 56, 5 7 ) , and c o n s e q u e n t l y , t h e  (58) and S c h o t t s k y discussed  (59) l a t t i c e d e f e c t t h e o r i e s .  the r e l o c a t i o n o f p r i m a r y c a t h o d i c and  Prenkel  Evans  (60)  anodic areas  a f t e r immersion of t h e e l e c t r o d e i n an e l e c t r o l y t e . I n summary, the s u r f a c e of a s i n g l e m e t a l  electrode  c o n s t i t u t e s a network of g a l v a n i c c e l l s to w h i c h e q u a t i o n ( l ) , neglecting i r r e v e r s i b i l i t i e s , i s applicable. The  e f f e c t o f s t r e s s e s , b o t h i n t e r n a l and  on the network o f g a l v a n i c c e l l s w i l l be  external,  considered.  Abundant e v i d e n c e e x i s t s t o show t h a t c o l d worked specimens a r e as much as 50 mv.  e l e c t r o n e g a t i v e to annealed  m e t a l specimens (1,9,13,15,16,17,18,26,27).  Cold working  causeB some work t o be s t o r e d i n the f o r m o f l a t e n t energy  33  (30,31).  S i n c e the end p r o d u c t s o f " l o c a l " g a l v a n i c a c t i o n  a r e g e n e r a l l y t h e same whether t h e specimen i s c o l d worked o r a n n e a l e d , a g r e a t e r energy change, and t h e r e f o r e , f r e e energy change, w i l l be i n t r o d u c e d i n t h e r e a c t i o n s . P r o b a b l y b o t h t h e a n o d i c and e a t h o d i c a r e a s a r e s h i f t e d i n a more a n o d i c d i r e c t i o n a c c o u n t i n g f o r t h e more e l e c t r o n e g a t i v e p o t e n t i a l . When a copper e l e c t r o d e i s immersed i n a s o l u t i o n i n w h i c h t h e cuprous o x i d e f i l m i s s t a b l e , t h e a p p l i c a t i o n o f t e n s i l e s t r e s s to t h e copper w i l l i n c r e a s e t h e i n t e r n a l energy o f t h e copper, and r u p t u r e t h e r e l a t i v e l y b r i t t l e cuprous o x i d e f i l m , when b o t h e l a s t i c and p l a s t i c s t r a i n cause movements o f t h e u n d e r l y i n g m e t a l .  The v e r y l e a s t o p e r a t i o n t h a t  w i l l happen w i l l be an i n c r e a s e i n p o r e s i z e i n t h e f i l m . The r u p t u r e o f t h e cuprous o x i d e f i l m w i l l i n c r e a s e t h e a n o d i c a r e a s , due t o the p r e s e n c e  o f copper m e t a l , w h i c h , w i t h t h e  i n c r e a s e d i n t e r n a l energy, w i l l s h i f t t h e e l e c t r o d e p o t e n t i a l i n an a n o d i c d i r e c t i o n .  P o s t - s t r e s s i n g decay of t h i s pot-  e n t i a l change i s caused b y i n c r e a s e d l o c a l p o l a r i z a t i o n s and regrowth of the oxide f i l m .  P l a s t i c d e f o r m a t i o n s , such as  t w i n n i n g o r s l i p p i n g , w i l l c r e a t e new a r e a s , p r o b a b l y to  similar  the g r a i n b o u n d a r i e s where o x i d e f i l m s , a s an e x t e n s i o n o f  the metal l a t t i c e , are i m p o s s i b l e .  Hence, s t r e s s e s s h o u l d  change t h e s t e a d y e l e c t r o d e p o t e n t i a l t o a s l i g h t l y more a n o d i c v a l u e b y t h e combined e f f e c t s o f i n c r e a s e d i n t e r n a l energy and a g r e a t e r f r a c t i o n o f t h e t o t a l s u r f a c e a r e a as anodes.  34  P o u r b a i x (61) has p r e s e n t e d a v e r y p r a c t i c a l a p p r o a c h t o the p r o b l e m o f c o r r o s i o n and  the d e t e r m i n a t i o n s of the s t a -  b i l i t y o f p a s s i v a t i n g f i l m s on the s u r f a c e of m e t a l s .  The  b a s i c p r i n c i p l e o f P o u r b a i x * s work i s t h a t a l l e q u i l i b r i u m conditions at metal surfaces f u n c t i o n s of two  c o n t a c t i n g aqueous s o l u t i o n s  independent v a r i a b l e s , pH and E, where E  e q u a l s the e q u i l i b r i u m e l e c t r i c a l p o t e n t i a l w i t h r e s p e c t hydrogen e l e c t r o d e .  to  the  E q u a t i o n s are d e v e l o p e d "between pH and Ei;  t h e s e e q u a t i o n s a r e t h e n p l o t t e d as a p o t e n t i a l - p H The  are  diagram.  surface of the p o t e n t i a l - p H diagram i s then d i v i d e d i n t o  t h r e e a r e a s : c o r r o s i o n , immunity, and p a s s i v a t i o n domains. These a r e a s a r e l i m i t e d b y an a r b i t r a r y d e f i n i t i o n , s e t f o r t h b y P o u r b a i x , f o r the c o r r o d a b i l i t y of a m e t a l :  a m e t a l cannot  c o r r o d e i f t h e s o l u b i l i t y of the substanoe w h i c h c o v e r s i t s surface i s l e s s than 10"  6  gram-ions p e r l i t e r .  does n o t mean t h a t the m e t a l cannot c o r r o d e : the agent must f o r m a p e r f e c t non-porous f i l m .  Passivation passivating  W h i l e the a p p l i -  c a t i o n i s l i m i t e d to e q u i l i b r i u m r e a c t i o n s i t nevertheless usefulness  i n s t r a i n p o t e n t i a l phenomena.  has  35  APPARATUS  AND  PROCEDURE  APPARATUS The a p p a r a t u s used i n t h e i n v e s t i g a t i o n i s q u i t e simple.  B a s i c a l l y i t c o n s i s t s o f two p a r t s , t h e t e s t  and t h e d e t e c t i o n a p p a r a t u s .  cell  The t e s t c e l l c a n b e s t be des-  c r i b e d b y r e f e r e n c e t o a diagram, F i g u r e 1.  I t consists of  a c y l i n d r i c a l g l a s s tube w i t h v e r t i c a l l y a l i g n e d n i p p l e s a t t h e t o p and b o t t o m so t h a t t h e t e s t w i r e w i l l p a s s the c e l l without c o n t a c t i n g the g l a s s .  through  The g l a s s tubes a t  t h e b o t t o m o f t h e t e s t c e l l a r e c a r e f u l l y s e a l e d w i t h 'Cenco  1  p a r a r u b b e r t a p e i n such a manner t h a t t h e w i r e s w i l l move f r e e l y t h r o u g h t h e p a r a r u b b e r t a p e , w h i l e a t the same time the e l e c t r o l y t i c  s o l u t i o n w i l l be h e l d w i t h i n t h e c e l l .  t i g u o u s w i t h t h e t e s t c e l l i s a c o n s t a n t temperature  Con-  bath.  The t e s t c e l l p r o j e c t s f r o m a h o l e i n t h e b o t t o m o f t h e b a t h , and i s h e l d i n p o s i t i o n w i t h a r u b b e r s t o p p e r , w h i c h a l s o s e r v e s t o r e t a i n t h e w a t e r o f t h e c o n s t a n t temperature  bath.  A s m a l l s i d e arm i s a v a i l a b l e on t h e t e s t c e l l i n o r d e r t o introduce the e l e c t r o l y t e without d i s t u r b i n g the wires a f t e r t h e y have been p l a c e d .  Three t e s t c e l l s i n o p e r a t i n g p o s i -  t i o n s a r e shown i n F i g u r e 2.  The complete assemblage i n c l u -  d i n g c o n s t a n t temperature b a t h , t h e r m o r e g u l a t o r , thermometer, s t i r r e r , w i r e s u p p o r t i n g d e x i o n framework, c l i p l e a d s t o  r  F i g u r e 1.  Test C e l l  37  Figure  2.  Arrangement o f T e s t C e l l s i n C o n s t a n t Temperature Bath  38  the t e s t w i r e s , and t h e hanging w e i g h t s i s shown p h o t o g r a p h i c a l l y i n F i g u r e 3.  The s t i r r e r i s mounted on a s e p a r a t e  framework t o e l i m i n a t e v i b r a t i o n s o f t h e t e s t w i r e . rubber covered a l l i g a t o r  The  c l i p l e a d s , attached to the t e s t  w i r e s above the d e x i o n framework, t r a n s m i t t h e p o t e n t i a l d i f f e r e n c e between t h e two w i r e s t o the measuring  apparatus.  The d e t e c t i o n a p p a r a t u s c o n s i s t e d o f a Type G Speedomax p o t e n t i a l r e c o r d e r (Model S, S e r i e s 6000) and a Leeds and H o r t h r u p n u l l b a l a n c i n g m i l l i v o l t p o t e n t i o m e t e r number 6 7 9 6 6 7 ) . advantages:  (serial  The use o f a Speedomax had t h r e e e s s e n t i a l  a continuous r e c o r d of the p o t e n t i a l d i f f e r e n c e  between t h e two w i r e s , a one and o n e - h a l f second b a l a n c e comp a r e d t o a 15 second b a l a n c e w i t h a manual p o t e n t i o m e t e r ,  and  a h i g h impedance, w h i c h e l i m i n a t e d s m a l l c u r r e n t s f l o w i n g between t h e w i r e s found i n a m a n u a l l y o p e r a t e d while achieving a balance. r a t e t o 0.5$.  potentiometer  The Speedomax gave r e a d i n g s a c c u -  U n f o r t u n a t e l y , the o n l y a v a i l a b l e Speedomax  had a range o f a p p r o x i m a t e l y 22 t o 54 m i l l i v o l t s .  Measuring  t h e p o t e n t i a l between a p a i r o f w i r e s gave s t r a i n p o t e n t i a l s i n t h e range 0 t o 25 m i l l i v o l t s and o c c a s i o n a l l y as h i g h as 40 mv.;  so t h a t t h e range o f t h e Speedomax was n o t c o n s i s t e n t  w i t h t h e range o f t h e s t r a i n p o t e n t i a l s .  This problem  was  e l i m i n a t e d by i n t r o d u c i n g a constant v o l t a g e from the m i l l i v o l t potentiometer i n s e r i e s w i t h the s t r a i n p o t e n t i a l .  The  r e a d i n g s t h e n f e l l w i t h i n the r a n g e o f the Speedomax e x c e p t  39  F i g u r e 3. Assemblage  of  Apparatus  40  f o r a^^higher p e a k s .  The peak v a l u e s c o u l d he o b t a i n e d b y  reducing the value o f the m i l l i v o l t potentiometer i n s e r i e s w i t h the s t r a i n p o t e n t i a l .  The m i l l i v o l t p o t e n t i o m e t e r was  u s e d t o c a l i b r a t e t h e Speedomax, as w e l l a s t o p r o v i d e a constant voltage source. Jones t e r m i n a l b l o c k s were used t o s u p p o r t t h e t e s t w i r e s on t h e d e x i o n framework, and t o i n s u l a t e t h e t e s t w i r e s f r o m t h e framework.  They a l l o w e d t h e a l l i g a t o r c l i p s t o be  a t t a c h e d above t h e p o s i t i o n o f support so t h a t a s much e x t r a neous movement as p o s s i b l e upon l o a d i n g t h e t e s t w i r e c o u l d be avoided. PROCEDURE A l l e l e c t r o l y t i c s o l u t i o n s were p r e p a r e d w i t h d i s t i l l e d water and a n a l y t i c a l r e a g e n t grade s a l t s .  The gram  e q u i v a l e n t w e i g h t o f p o t a s s i u m n i t r a t e was t a k e n as t h e f o r m u l a w e i g h t , and t h e gram e q u i v a l e n t w e i g h t o f c u p r i c s u l f a t e was t a k e n as o n e - h a l f t h e f o r m u l a w e i g h t .  P o r example, 35.276  grams o f p o t a s s i u m n i t r a t e and 31.461 grams o f c u p r i c s u l f a t e ( h y d r a t e d ) were d i s s o l v e d t o g i v e f i v e l i t e r s o f 0.05N p o t a s sium n i t r a t e and 0.05N c u p r i c s u l f a t e , r e s p e c t i v e l y .  Pre-  v i o u s l y , t h e d i s t i l l e d w a t e r had b e e n a i r b l o w n f o r one h a l f hour t o i n s u r e a i r s a t u r a t i o n . I n a l l c a s e s , s i z e #22 B & S h a r d and s o f t w i r e specimens were used as t h e t e s t specimens;  copper  t h e copper  41  w i r e was a good commercial grade as p u r c h a s e d f r o m t h e manufacturer.  P r i o r t o use, t h e w i r e was l e f t f r e e l y exposed t o  the  atmosphere a t room t e m p e r a t u r e .  Immediately h e f o r e u s i n g  the  w i r e specimen was c l e a n e d o f d i r t and g r e a s e , f i r s t  by  d r a w i n g t h r o u g h aKLeenex t i s s u e soaked w i t h c a r b o n t e t r a c h l o r i d e , and second b y d r a w i n g t h r o u g h a k l e e n e x t i s s u e soaked w i t h acetone.  The c l e a n e d w i r e , h e l d b y the Jones t e r m i n a l  b l o c k , was t h e n t h r e a d e d t h r o u g h t h e c e l l .  The  alligator  c l i p s were a t t a c h e d t o i n s u r e t h a t no movement would o c c u r l a t e r , as a r e s u l t o f t h e i r a d d i t i o n o r t h r o u g h t e n s i o n i n t h e lead wires.  The w i r e specimen was l o a d e d w i t h t h e b a l a n c e pan,  w e i g h i n g 233 grams, d u r i n g t h e a p p l i c a t i o n o f the p a r a r u b b e r tape.  The r i g h t hand w i r e ( u n s t r a i n e d ) was always i n s t a l l e d  c o m p l e t e l y f i r s t t o i n s u r e t h a t t h e w i r e s would n o t be c r o s s e d i n the c e l l . In  the n e x t s t e p i n t h e p r o c e d u r e f o r s t r a i n p o t -  e n t i a l measurements t h e s o l u t i o n i s added t o t h e c e l l , the  with  s w i t c h c l o s i n g the m e a s u r i n g c i r c u i t i n the open p o s i t i o n .  A f t e r t h e e l e c t r o l y t e had c o n t a c t e d the specimen f o r twentyf i v e m i n u t e s , the Speedomax was c a l i b r a t e d b y a p p l y i n g const a n t known v o l t a g e s f r o m t h e m i l l i v o l t p o t e n t i o m e t e r . at  Then  t h i r t y m i n u t e s , t h e p o t e n t i a l d i f f e r e n c e between t h e two  w i r e s i n t h e t e s t c e l l and the known s e r i e s v o l t a g e f r o m t h e p o t e n t i o m e t e r was i n t r o d u c e d t o t h e Speedomax.  When a s t e a d y  p o t e n t i a l d i f f e r e n c e between t h e two w i r e s was i n d i c a t e d b y  42  the Speedomax, t h e w e i g h t s were added t o t h e l e f t w i r e . was  Care  e x e r c i s e d i n a d d i n g t h e w e i g h t s t o p r e v e n t any j a r r i n g o f  t h e l e f t w i r e , s i n c e impact l o a d i n g would a p p l y a g r e a t e r momentary s t r e s s , and c o u l d n o t he r e p r o d u c e d .  The method f o r  a d d i n g w e i g h t s c a n v a r y f r o m s u c e s s i v e l o a d i n g s o f 1, 2, 1, 1. and 1 k i l o g r a m s t o t o t a l l o a d i n g s o f 4, 5, o r 6 k i l o g r a m s . I n s u c c e s s i v e l o a d i n g s , enough time was t a k e n between a d d i t i o n of w e i g h t s f o r s u f f i c i e n t t i m e - p o t e n t i a l r e c o r d i n g , t h a t i s , for  the s t r a i n p o t e n t i a l t o decay t o a steady v a l u e .  The  above p r o c e d u r e was a l t e r e d f o r i n v e s t i g a t i o n s t o determine the e x i s t e n c e o r non-existence o f an i n d u c t i o n p e r i o d ; here, t h e Speedomax was i n t h e c i r c u i t f r o m t h e a d d i t i o n o f t h e e l e c t r o l y t e and t h e w e i g h t s may be added t o t h e l e f t w i r e a t any d e s i r e d t i m e a f t e r t h e s o l u t i o n h a s been added t o t h e c e l l . Ho attempt was made t o d e t e r m i n e t h e e f f e c t o f t h e l e n g t h o f t h e w i r e exposed t o t h e s o l u t i o n . r e p o r t e d t h a t t h i s e f f e c t was n e g l i g i b l e .  McDonnell  (24) .  I n every case,  the l e n g t h o f t h e exposed w i r e was t h e maximum a l l o w e d b y t h e t e s t c e l l , that i s , twenty-three centimeters.  43  EXPERIMENTAL RESULTS A. TESTS USING- SIZE #22 B & S HARD COPPER WIRE I N O.OQ5N POTASSIUM NITRATE SOLUTION. The r e s u l t s o f e i g h t s u c c e s s f u l t e s t r u n s f o r h a r d copper w i r e i n 0.005N p o t a s s i u m n i t r a t e a r e l i s t e d i n T a b l e I , A p p e n d i x I . A t y p i c a l r e s u l t o b t a i n e d w i t h t h e Speedomax i s shown i n F i g u r e 4, A p p e n d i x I . A s i m p l i f i e d s t a t i s t i c a l analysis  ,(62) was made on t h e e i g h t t e s t r u n s t o g i v e t h e  following table of r e s u l t s : LOAD ON LEFT WIRE (K3SS) 5 10  MAXIMUM STRAIN POTENTIAL -1.63 ±0.12 -0.17 ±0.04  TABLE A. MAXIMUM STRAIN POTENTIALS OP HARD COPPER WIRE FOR DIFFERENT LOADS. P o t e n t i a l s a r e b a s e d on t h e hydrogen r e d u c t i o n s c a l e . I t s h o u l d be n o t e d , t h a t even t h e a d d i t i o n o f t h e b a l a n c e p a n t o t h e l e f t w i r e caused an e l e c t r o n e g a t i v e p o t e n t i a l s h i f t .  This  a f f e c t i s b e l i e v e d t o be caused b y p o l a r i z a t i o n e f f e c t s .  These  p o l a r i z a t i o n e f f e c t s would a r i s e t h r o u g h d i s t u r b i n g t h e e l e c t r o l y t i c f i l m i n contact w i t h the wire by the a d d i t i o n of the f i r s t weights.  I t f o l l o w s , t h e n , t h a t a l o a d o f 10 k g s .  would be more s i g n i f i c a n t , s i n c e i t was added t o a t a u t w i r e # The s t a t i s t i c a l a n a l y s i s c o n s i s t s o f t h e average s t r a i n p o t e n t i a l p l u s o r minus t h e s t a n d a r d d e v i a t i o n .  44  w h i c h would r e s u l t i n l e s s d i s t u r b a n c e o f the e l e c t r o l y t i c  film.  Ho e l o n g a t i o n s h o u l d be observed i n t h e s t r a i n e d w i r e w i t h t h e addition of a t e n kilogram load.  A load of eleven kilograms  caused t h e s t r a i n e d w i r e t o e l o n g a t e s l i g h t l y and r u p t u r e . B. TESTS USING- SIZE #22 B & S SOFT COPPER WIRE I H 0.005N POTASSIUM NITRATE SOLUTION. E x p e r i m e n t a l t e s t r u n s were made a t 25.0° C , 40.0° C., and 60.0° C.j t h e r e s u l t s o f t h i r t e e n s u c c e s s f u l r u n s a t 25.0° C , t e n s u c c e s s f u l r u n s a t 40.0°C., and f i v e s u c c e s s f u l r u n s a t 60.0° C. a r e g i v e n i n A p p e n d i x I i n T a b l e s I I , I I I , and I T , r e s p e c t i v e l y .  A l l measurements were made w i t h t h e  Speedomax, and t y p i c a l e x p e r i m e n t a l r e s u l t s a r e shown i n F i g u r e s 5, 6, and 7, A p p e n d i x I .  Again a s i m p l i f i e d  statis-  t i c a l a n a l y s i s was made on t h e r e s u l t s t o g i v e t h e f o l l o w i n g table: TEMP. °C 25  40  60  WEIGHT ON LEFT WIRE (KGS.)  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS 0.00 -5.48 + 1.58 -16.78 ±2.67 -20.52 ±2.01 0.00 - 6.62 ±2.38 -18.96 ±2.63 -29.02 ±3.16 0.00 - 7.99±1.33 -18.05 ±1.81 -32.32 ±7.1  3 4 5 6 3 4 5 6 3 4 5 6 i  DIFFERENT TEMPERATURES.  -nrvn  T I T i,ii.n.iL>-nvKTm  45  F i g u r e 8 shows t h e l o g a r i t h m o f t h e maximum s t r a i n p o t e n t i a l for  a load of s i x kilograms  t o he e s s e n t i a l l y l i n e a r w i t h t h e  r e c i p r o c a l of the absolute temperature.  The maximum s t r a i n  p o t e n t i a l shows a l a r g e s t a n d a r d d e v i a t i o n a t 60.0° C. i n d i c a t i n g t h a t i n s u f f i c i e n t t e s t r u n s have been done a t t h i s temperature f o r the s t a t i s t i c a l a n a l y s i s . An i m p o r t a n t  o b s e r v a t i o n t h a t appeared i n e v e r y t e s t  r u n w i t h s i z e #22 B & S s o f t copper w i r e was t h a t elongation begins a t a load of four kilograms nal  appreciable  and t h a t e x t e r -  e l o n g a t i o n accompanies a l o a d o f f i v e and s i x k i l o g r a m s .  C. TESTS USING- SIZE #22 B' & S SOFT COPPER WIRE I N 0.05U POTASSIUM NITRATE SOLUTION. Experimental  t e s t r u n s were made a t 25.0° C ,  40.0°  C., and 60.0° C ; t h e r e s u l t s o f e l e v e n s u c c e s s f u l r u n s a t 25.0° C , f o u r s u c c e s s f u l r u n s a t 40.0° C , and f o u r  success-  f u l r u n s a t 60.0° C. a r e g i v e n i n t h e Appendix i n T a b l e s V, V I , and V I I , r e s p e c t i v e l y .  A l l measurements were made w i t h  the Speedomax, and t y p i c a l s t r a i n p o t e n t i a l - t i m e c u r v e s a r e shown i n F i g u r e s 9, 10, and 1 1 , Appendix I . Table C shows the r e s u l t s o f a s i m p l i f i e d s t a t i s t i c a l a n a l y s i s *  46  TEMP.  °c.  WEIGHT ON LEFT WIRE (ESS. )  25  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS ) - 4.86 * 1.52 -17.38 ± 1.84 -21.60 ± 0.86 - 7.88 ± 0.41 -26.83 * 3.50 -34.02 ± 0.91 - 6.25 * 1.17 -18.52 ± 2.03 -27.47 ± 1.21  4 5 6 4 5 6 4 5 6  40 60  TABLE 0. MAXIMUM STRAIN POTENTIAL FOR DIFFERENT LOADS AT DIFFERENT TEMPERATURES. The r e s u l t s f o r 60.0° C. i n d i c a t e  t h a t t h e maximum s t r a i n  p o t e n t i a l i s lower a t t h i s temperature.  I t i s more l i k e l y ,  t h a t t o o few t e s t r u n s were made t o o b t a i n a s u i t a b l e s a m p l i n g . D. TESTS USING SIZE #22 B & S SOFT COPPER WIRE I N 0.5N POTASSIUM NITRATE  SOLUTION.  E x p e r i m e n t a l t e s t r u n s were made a t 25.0° 40.0° C ,  and 60.0° C ;  C,  the r e s u l t s of f i v e successful t e s t  r u n s a t each t e m p e r a t u r e a r e g i v e n i n Appendix I i n T a b l e s V I I I , I X , and X.  A l l measurements were made w i t h t h e Speed-  omax, and t y p i c a l s t r a i n p o t e n t i a l - t i m e c u r v e s a r e shown i n F i g u r e s 12, 1 3 , and 14, Appendix I . of a s i m p l i f i e d s t a t i s t i c a l  analysiss  Table D shows t h e r e s u l t s  47  TEMP. °C  WEIGHT ON LEFT WIRE (KGS.) 4 5 6 •4 5 6 4 5 6  25 40 60  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS) - 7.14 ± 2.38 -15.84 ± 1.84 -24.28 ± 1.50 - 7.51 ± 1.06 -21.03 ± 1 . 5 0 -27.69 ±1.48 - 8.43 -15.36 -33.50  TABLE D. MAXIMUM STRAIN POTENTIAL FOR DIFFERENT LOADS AT DIFFERENT TEMPERATURES. F i g u r e 15 shows t h e l o g a r i t h m o f t h e maximum s t r a i n p o t e n t i a l f o r a l o a d o f s i x k i l o g r a m s t o he e s s e n t i a l l y l i n e a r w i t h t h e r e c i p r o c a l of the absolute  temperature.  E. TESTS USING SIZE #22 B & S SOFT COPPER WIRE I N 0.05N CUPRIC SULFATE  SOLUTION.  Three e x p e r i m e n t a l t e s t r u n s were made a t 25.0° C. i n order t o reproduce  t h e r e s u l t s o f D u d l e y (26) and E l l i o t t  (27) s i n c e t h e y used t e s t w i r e s w h i c h had been e s p e c i a l l y p r e p a r e d f o r s t r a i n p o t e n t i a l work. a r e shown i n Table X I , A p p e n d i x I .  These e x p e r i m e n t a l r e s u l t s The average maximum s t r a i n  p o t e n t i a l f o r l o a d s of f o u r , f i v e and s i x k i l o g r a m s were -1.00, -2.33, and -4.44 mv., r e s p e c t i v e l y .  These compare f a v o u r a b l y  w i t h v a l u e s o b t a i n e d b y E l l i o t t , w h i c h were -0.53, -3.20, and -4.85 mv.  D u d l e y o b t a i n e d a v a l u e o f -4.47 mv. f o r a l o a d o f  s i x kilograms.  T h i s t h e n i n d i c a t e s t h a t t h e purchased  com-  m e r c i a l annealed w i r e was v e r y s i m i l a r i n i t s p r o p e r t i e s t o  \  48  the p a r t i c u l a r copper w i r e used b y t h e above w o r k e r s .  A  t y p i c a l s t r a i n p o t e n t i a l - t i m e curve i s shown i n F i g u r e 16, Appendix I . F. SUCCESSIVE LOADING- VERSUS TOTAL LOADING. S i x experimental  t e s t r u n s were made t o d e t e r m i n e  the e f f e c t on t h e s t r a i n p o t e n t i a l o f a d d i n g t h e w e i g h t s t o t a l l y i n groups o f f o u r , f i v e o r " s i x k i l o g r a m s as compared t o t h e s u c c e s s i v e l o a d i n g o f one p l u s two, p l u s one, p l u s one, and p l u s one k i l o g r a m up t o a t o t a l l o a d o f s i x k i l o g r a m s . The r e s u l t s i n d i c a t e t h a t t h e magnitude o f t h e maximum s t r a i n p o t e n t i a l i s t h e same f o r t o t a l l o a d i n g as f o r s u c c e s s i v e loading.  Shock o r impact l o a d i n g t h r o u g h i n a b i l i t y t o  s m o o t h l y ease t h e w e i g h t s onto t h e b a l a n c e p a n w i l l cause a l a r g e r s t r a i n p o t e n t i a l than i s normally  encountered.  G. MEASUREMENTS OF THE pH OF THE TEST CELL SOLUTION BEFORE AND AFTER THE EXPERIMENTAL TEST RUNS. A l l pH measurements were made w i t h a Model G Beckman pH M e t e r and a r e l i s t e d i n Table XII,- Appendix I . The i n i t i a l pH i n a l l t e s t s was 5.7.  The pH showed a s l i g h t  increase during e l e c t r o l y s i s which could i n d i c a t e a d e p l e t i o n o f oxygen o r an i n c r e a s e i n h y d r o x y l i o n s i n s o l u t i o n - .  In  a l l c a s e s , t h e change i n t h e v a l u e o f t h e pH i s independent o f t h e l e n g t h o f time t h e copper w i r e c o n t a c t s t h e e l e c trolyte .  49  H. STRAIN POTENTIAL-TIME RELATIONSHIPS. Typical  s t r a i n p o t e n t i a l - t i m e c u r v e s a r e shown  p l o t t e d on r e c t a n g u l a r c o o r d i n a t e s b y t h e Speedomax i n t h e A p p e n d i x i n F i g u r e s 4, 5, 6, 7, 9, 10, 1 1 , 12, 1 3 , and 14. The maximum s t r a i n p o t e n t i a l o c c u r s a t t h e i n s t a n t o f t h e a d d i t i o n of the weights to the l e f t w i r e .  This p o t e n t i a l  d i f f e r e n c e between t h e two w i r e s d i m i n i s h e s w i t h time a steady v a l u e i s reached.  until  I n a l l cases, the p o t e n t i a l  dif-  f e r e n c e between t h e two w i r e s , a f t e r t h e maximum s t r a i n p o t e n t i a l had decayed t o a s t e a d y v a l u e , was s l i g h t l y e l e c t r o negative to the p o t e n t i a l value e x i s t i n g before the weights were added.  D u d l e y (26) found t h a t t h e s t r a i n e d w i r e always  remained s l i g h t l y e l e c t r o n e g a t i v e t o t h e u n s t r a i n e d w i r e . I n t h i s work, t h e a u t h o r found t h a t i f t h e l e f t hand w i r e ( s t r a i n e d ) was e l e c t r o p o s i t i v e t o t h e r i g h t w i r e on immersion i n t h e e l e c t r o l y t e w i t h no l o a d added, t h e n when t h e s t r a i n p o t e n t i a l decayed t o a s t e a d y v a l u e , t h i s v a l u e was e l e c t r o p o s i t i v e b u t n o t as l a r g e as t h e i n i t i a l immersion v a l u e . I n o t h e r words i f t h e l e f t hand w i r e had o r i g i n a l l y been covered w i t h predominately  e a t h o d i c a r e a s r e l a t i v e t o t h e r i g h t hand  w i r e , t h e i n f l u e n c e o f t h e s e e a t h o d i c a r e a s was n o t c o m p l e t e l y u p s e t b y l o a d i n g t h e l e f t w i r e and subsequent d e c a y o f t h e resulting electronegative s t r a i n potential.  I t was f o u n d t h a t the d e c a y of the s t r a i n p o t e n t i a l w i t h time f o r copper i n a e r a t e d KHO3 s o l u t i o n s f o l l o w e d a logarithmic  r e l a t i o n s h i p of the B = k  where  form.  In ( a t + a t ' + l )  (7.)  E = the s t r a i n p o t e n t i a l , m i l l i v o l t s t = time, minutes t'-  zero c o n s t a n t t i m e e r r o r , m i n u t e s  k, a = c o n s t a n t s . Some i n i t i a l t i m e was  r e q u i r e d i n a l l c a s e s "before t h e d e c a y  f o l l o w e d the l o g a r i t h m i c  r e l a t i o n s h i p of equation ( 7 . ) .  i n i t i a l time v a r i e d f r o m 0.1 m i n u t e s t o as much as 15  This  minutes.  I n t h e same manner, c o n s i d e r a b l e d e c a y i n t h e s t r a i n p o t e n t i a l r e s u l t e d b e f o r e e q u a t i o n (7.) became v a l i d .  This i n i t i a l  d e c a y i n p o t e n t i a l v a r i e d f r o m 0.5 m i l l i v o l t s t o as much as 15  millivolts. The c o n s t a n t s i n e q u a t i o n ( 7 . ) were e v a l u a t e d f o r  a p p r o x i m a t e l y 120 d e c a y c u r v e s .  The r e s u l t s cover t h e t h r e e  l o a d s of 4, 5, and 6 k i l o g r a m s w h i c h r e s u l t e d i n a s t r a i n p o t e n t i a l and hence a d e c a y c u r v e . the t h r e e t e m p e r a t u r e s  To t h e above must be added  under i n v e s t i g a t i o n , as w e l l as t h e  t h r e e v a r i a t i o n s i n t h e c o n c e n t r a t i o n o f the KNO3 e l e c t r o l y t e . The manner i n w h i c h t h e c o n s t a n t s were  determined  may be seen i n the sample c a l c u l a t i o n i n c l u d e d i n A p p e n d i x I I . The v a l u e s so o b t a i n e d a r e i n c l u d e d i n A p p e n d i x I I i n Tables XIV, XV, and  XVI.  51  I t was a n t i c i p a t e d t h a t t h e l o g a r i t h i m o f t h e r a t e c o n s t a n t , k, i n e q u a t i o n (7.) would h e a r a r e l a t i o n s h i p w i t h the r e c i p r o c a l o f the a b s o l u t e temperature. s h i p i s found t o e x i s t .  Ho such r e l a t i o n -  The v a l u e s o f t h e r a t e  constant  v a r i e d randomly f r o m 0.93 t o 7.56 m i l l i v o l t s p e r m i n u t e . This s i t u a t i o n e x i s t e d even though t h e l o a d , t h e t e m p e r a t u r e , and t h e c o n c e n t r a t i o n o f  KHO3  be r e g a r d e d as p a r a m e t e r s .  In  a l l c a l c u l a t i o n s t h e z e r o c o n s t a n t t i m e e r r o r was found t o be n e g a t i v e and v a r y i n g i n v a l u e . Ho r e l a t i o n s h i p was f o u n d t o e x i s t between e i t h e r the range o f time o r t h e range of p o t e n t i a l , f o r w h i c h t h e l o g a r i t h m i c l a w was v a l i d , and t h e maximum s t r a i n p o t e n t i a l . An e f f o r t was made t o f i t a p a r a b o l i c r e l a t i o n s h i p , to  the p o r t i o n of the curve immediately preceeding t h e v a l i d  l o g a r i t h m i c s e c t i o n , t o no a v a i l .  I n m o s t cases, the i n i t i a l  decay i s so r a p i d w i t h t i m e as t o b e beyond t h e s i g n i f i c a n c e of  t h e measuring equipment.  The i n i t i a l decay may be c o n s i -  d e r e d t o approximate a l i n e a r r e l a t i o n s h i p , p a s s i n g t h r o u g h the o r i g i n , w i t h a v e r y large slope.  Here a g a i n t h e decay  was found t o be so r a p i d i n most cases as t o be beyond t h e s i g n i f i c a n c e of t h e measuring equipment.  The t h i c k n e s s o f t h e  pen l i n e drawn b y t h e Speedomax i s i n t h e o r d e r o f 0.1 m i n u t e s on t h e c h a r t s c a l e .  A f e a t u r e of s i g n i f i c a n c e , observed i n almost every decay c u r v e , was  t h a t the r a t e of d e c a y became even slower  t h a n t h a t o b s e r v e d f o r the l o g a r i t h m i c r a t e ^ b e f o r e a s t e a d y p o t e n t i a l was  attained.  53  DISCUSSION The absence o f d e l e c t a b l e s t r a i n p o t e n t i a l s f o r s t r e s s e s below the e l a s t i c l i m i t , and t h e g r e a t e r e l e c t r o n e g a t i v e s t r a i n f o r s o f t copper w i r e t h a n f o r hard copper w i r e supp o r t the b e l i e f t h a t s t r a i n p o t e n t i a l s r e s u l t c h i e f l y f r o m the r u p t u r e o f a s u r f a c e f i l m ; h a r d copper w i r e e x h i b i t s v e r y l i t t l e s t r a i n b e f o r e t h e m e t a l r u p t u r e s w h i l e s o f t copper w i r e elongates e x t e n s i v e l y w i t h loads w e l l below the p o i n t of f r a c ture.  S o f t copper w i r e does n o t p o s s e s s a c l e a r l y d e f i n e d  e l a s t i c l i m i t b u t i t was n o t i c e d throughout  the experimental  work, as mentioned b e f o r e , .that l o a d s up t o t h r e e k i l o g r a m s on s i z e #22 w i r e g i v e v e r y l i t t l e s t r a i n , a l o a d o f f o u r k i l o grams g i v e s a p p r e c i a b l e s t r a i n , and l o a d s o f f i v e and s i x kilograms give excessive s t r a i n .  From t h e e x p e r i m e n t a l  results  i t may be seen t h a t , t h e s t r a i n p o t e n t i a l r e s u l t i n g f r o m a l o a d o f t h r e e k i l o g r a m s i s n e g l i g i b l e , the s t r a i n p o t e n t i a l r e s u l t i n g f r o m a l o a d o f f o u r k i l o g r a m s i s a p p r e c i a b l e , and t h e s t r a i n p o t e n t i a l s r e s u l t i n g f r o m l o a d s o f f i v e and s i x k i l o grams a r e l a r g e . In  a l l t e s t r u n s , t h e s t r a i n p o t e n t i a l decayed w i t h  t i m e a f t e r l o a d i n g , i n t h e same smooth c u r v e s shown i n F i g u r e 5. The magnitude o f t h e s t r a i n p o t e n t i a l f o r a g i v e n s t r e s s was found t o be s t a t i s t i c a l l y s i g n i f i c a n t , r e p r o d u c i b l e and i n complete a c c o r d w i t h t h e r e s u l t s o b t a i n e d by M c D o n n e l l  54  (24),  D u d l e y ( 2 6 ) , and E l l i o t t  (27).  The f i l m t h e o r y i s shown to he thermo dynamic a l l y f e a s i b l e u s i n g p o t e n t i a l - p H diagrams as proposed by (61).  Pourbaix  The r e g i o n of c o n c e r n i s f i x e d by the pH and the  log  of the s o l u t i o n , r e f e r e n c e t o P o u r b a i x s p o t e n t i a l - p H !  d i a g r a m f o r the system Cu - B^O  shows t h a t cuprous o x i d e i s  completely s t a b l e . Some f a c t o r s a f f e c t i n g the s t r a i n p o t e n t i a l w i l l discussed.  be  These f a c t o r s c o u l d have a c o n s i d e r a b l e i n f l u e n c e  on the f o r m a t i o n o f an o x i d e f i l m . ships t a c i t l y  Most m a t h e m a t i c a l r e l a t i o n -  assume t h a t , so soon as f r e s h m e t a l s u r f a c e i s  a v a i l a b l e , absorbed oxygen w i l l be f o u n d w a i t i n g t h e r e to f o r m the oxygen atoms of t h e o x i d e l a t t i c e .  The  solution interface  i n e q u i l i b r i u m w i l l be d i s t u r b e d by the copper w i r e t h r o u g h the s o l u t i o n .  The n a t u r e of the m e c h a n i c a l p r o p e r t i e s  of the exposed copper m e t a l may chemical behavior  elongating  be i m p o r t a n t , as w e l l as  of the copper m e t a l .  I t i s altogether  the likely  t h a t an i n i t i a l p e r i o d of t i m e would be r e q u i r e d b e f o r e some mechanism became the c o n t r o l l i n g f a c t o r i n s u c h a non-homogeneous p r o c e s s as s t r a i n i n g the copper w i r e .  I t i s possible  t h a t the p r o c e s s w i l l not be c o n t r o l l e d by a s i n g l e mechanism until  the exposed s u r f a c e i s c o m p l e t e l y covered w i t h a f r e s h  cuprous o x i d e f i l m .  I n w h i c h c a s e , as above, no s i n g l e mecha-  n i s m w i l l l i k e l y be r a t e c o n t r o l l i n g . A s a t i s f a c t o r y e x p l a n a t i o n f o r the i n c r e a s e i n t h e  ,  55  magnitude o f t h e s t r a i n p o t e n t i a l w i t h i n c r e a s i n g t e m p e r a t u r e i s , as y e t , unknown.  One p o s s i b i l i t y i s " t h a t the d e c r e a s e d  s o l u b i l i t y of oxygen w i t h i n c r e a s e d  temperatures w i l l r e s u l t  i n l e s s regrowth of the oxide f i l m d u r i n g o r immediately a f t e r t h e s t r a i n i n g ; t h i s w i l l r e s u l t i n a g r e a t e r amount o f b a r e w i r e b e i n g exposed f o r a g i v e n s t r e s s .  Since the o v e r a l l  e l e c t r o d e p o t e n t i a l of t h e s t r e s s e d w i r e i s t h e a r e a w e i g h t e d mean o f t h e e a t h o d i c  o x i d e f i l m a r e a s and t h e a n o d i c b a r e m e t a l  a r e a s , t h e g r e a t e r the a r e a of b a r e m e t a l exposed t h e g r e a t e r w i l l be the e l e c t r o n e g a t i v i t y of t h e e l e c t r o d e p o t e n t i a l . d e c r e a s e i n t h e amount d f r e g r o w t h over t h e s h o r t between t h e b e g i n n i n g  A  interval  o f t h e a p p l i c a t i o n o f t h e s t r e s s and t h e  r e c o r d i n g o f t h e maximum s t r a i n p o t e n t i a l w i l l be e s p e c i a l l y t r u e i f t h e r a t e of growth o f t h e o x i d e f i l m i s c o n t r o l l e d b y the r a t e o f d i f f u s i o n o f oxygen t o t h e s u r f a c e o f t h e m e t a l . Another p o s s i b l e explanation f o r the s t r a i n p o t e n t i a l - t e m p e r a t u r e r e l a t i o n s h i p i s t h a t t h e r a t e o f change w i t h tempe r a t u r e , i n an a n o d i c d i r e c t i o n , o f t h e e l e c t r o d e p o t e n t i a l Of t h e anode p r o c e s s e s i s g r e a t e r t h a n t h a t o f t h e cathode processes. equation tion. due  The t e m p e r a t u r e dependence i s u s u a l l y g i v e n b y an  of the Arrhenius  t y p e i n v o l v i n g ah e n e r g y o f a c t i v a -  T h i s i n d i c a t e s t h a t t h e change i n e l e c t r o d e p o t e n t i a l  t o s t r e s s c o r r e s p o n d s to a r a t e r e a c t i o n and t h a t  this  change i n p o t e n t i a l i s p r o p o r t i o n a l t o t h e r a t e o f t h e r e a c t i o n . However, the e x a c t r e l a t i o n s h i p between t h e r a t e and e l e c t r o d e  56  p o t e n t i a l change i s known o n l y d u r i n g p a r t o f t h e d e c a y process. I t has he en shown t h a t when copper s u f f e r s p l a s t i c d e f o r m a t i o n t h e r e i s a l a r g e change i n p o t e n t i a l i n t h e e l e c t r o n e g a t i v e d i r e c t i o n , and t h a t t h i s p o t e n t i a l change d i m i n i s h e s in  time w i t h a n e g a t i v e a c c e l e r a t i o n .  F i n a l l y the e l e c t r o d e  p o t e n t i a l approaches a s y m p t o t i c a l l y some v a l u e a l i t t l e g r e a t e r t h a n the i n i t i a l v a l u e b e f o r e s t r a i n . the i n i t i a l v a l u e .  T h i s v a l u e never  reaches  C l e a r l y t h e n , t h i s i n d i c a t e s two d i f f e r e n t  e f f e c t s caused b y p l a s t i c d e f o r m a t i o n .  The f i r s t  effect, that  of the r u p t u r e o f the s u r f a c e f i l m , i s g r a d u a l l y d i s p l a c e d b y the r e p a i r o f t h e f i l m , hence t h e p o t e n t i a l change caused b y t h i s e f f e c t w i l l g r a d u a l l y r e t u r n to z e r o a s t h e s u r f a c e f i l m is repaired.  The p o t e n t i a l change, i t has been shown, does  not r e t u r n to z e r o , t h i s f a c t can be e x p l a i n e d b y c o n s i d e r i n g t h a t t h e m e t a l system has been p e r m a n e n t l y a l t e r e d and h a s had i t s i n t e r n a l energy i n c r e a s e d g i v i n g r i s e to an i n c r e a s e i n p o t e n t i a l of t h e m e t a l . I t i s e v i d e n t f r o m t h e e x p e r i m e n t a l r e s u l t s t h a t the magnitude of t h e s t r a i n p o t e n t i a l i s independent o f the concentration  of potassium n i t r a t e i n the s o l u t i o n ;  to a r i s e because t h e a c t i v i t y of copper i o n s w i l l  this i s felt r e m a i n essen-  t i a l l y c o n s t a n t i n t h e s e systems. Examination  of t h e decay c u r v e s show an a p p r o x i m a t i o n  to a l i n e a r c u r v e f o r the i n i t i a l p a r t o f the decay c u r v e .  57 However, f o r most o f t h e d e c a y c u r v e s , t h e i n i t i a l decay i s "beyond t h e s i g n i f i c a n c e o f the t i m e c o o r d i n a t e , making i t impossible to evaluate a v a l i d l i n e a r r e l a t i o n s h i p .  I n the  c u r v e s f o r w h i c h t h e time c o o r d i n a t e i s r e a d i l y s c a l e d a d e f i n i t e though s l i g h t c u r v a t u r e f r o m zero time i s o b s e r v e d ,  prev-  e n t i n g an e x a c t l y l i n e a r f u n c t i o n b e i n g e s t a b l i s h e d . A l i n e a r r e l a t i o n s h i p would p a s s t h r o u g h t h e o r i g i n w i t h t h e s t r a i n p o t e n t i a l d i r e c t l y p r o p o r t i o n a l to t h e t i m e . would f o r m t h e p r o p o r t i o n a l i t y c o n s t a n t .  The r a t e c o n s t a n t Such a r a t e c o n s t a n t  f o r t h e e x p e r i m e n t a l d e c a y c u r v e s w o u l d be i n the o r d e r o f 20 to 100 t i m e s l a r g e r t h a n t h e v a l u e s shown i n Appendix I I f o r a logarithmic rate. An e f f o r t was made t o f i t a p a r a b o l i c r e l a t i o n s h i p to t h e p o r t i o n of t h e curve p r e c e e d i n g t h e v a l i d l o g a r i t h m i c r e l a t i o n s h i p , to noaxrail. I t was found t h a t the decay o f t h e s t r a i n p o t e n t i a l w i t h time f o l l o w e d a l o g a r i t h m i c r e l a t i o n s h i p o f the f o r m o f e q u a t i o n ( 7 . ) . An example i s shown p l o t t e d i n F i g u r e 1 7 . Some i n i t i a l time i s r e q u i r e d i n a l l cases b e f o r e t h e decay c u r v e followed the l o g a r i t h m i c r e l a t i o n s h i p . The c o n s t a n t s i n e q u a t i o n (7.) were e v a l u a t e d f o r a p p r o x i m a t e l y 120 d e c a y c u r v e s .  Tables XIV, XV, and XVI show  no r e l a t i o n s h i p between t h e l o g a r i t h m o f t h e r a t e c o n s t a n t and t h e r e c i p r o c a l o f t h e a b s o l u t e temperature  i n t h e manner  o f A r r h e n i u s , even though t h e l o a d and/or t h e c o n c e n t r a t i o n  58  "be c o n s i d e r e d  as p a r a m e t e r s .  No r e l a t i o n s h i p i s seen t o e x i s t between t h e r a t e constant  and t h e c o n c e n t r a t i o n ,  t h e l o a d , t h e maximum s t r a i n  p o t e n t i a l , o r the i n i t i a l time o r p o t e n t i a l r e q u i r e d t o make equation  (7.) v a l i d . I n a l l c a s e s , the zero  t i v e and v a r i e s i n v a l u e .  constant  t i m e e r r o r i s nega-  V a l u e s i n c l u d e d as 0.00 a r e b e f o r e  the s i g n i f i c a n c e i s removed i n t h e o r d e r o f — 0 . 0 0 4 t o — 0 . 0 0 0 1 minutes• A f e a t u r e o f s i g n i f i c a n c e , o b s e r v e d i n almost e v e r y decay c u r v e , i s t h a t t h e r a t e of d e c a y became even s l o w e r t h a n t h a t observed f o r t h e l o g a r i t h m i c r a t e .  The c o m p l e x i t y  of the  decay c u r v e s i n d i c a t e t h a t s e v e r a l f a c t o r s a r e i m p o r t a n t i n c o n t r o l l i n g t h e r e g r o w t h o f t h e s u r f a c e f i l m a f t e r a nonhomogeneous p r o c e s s . In concluding  t h e d i s c u s s i o n , i t w i l l be emphasized  that a l l the r e s u l t s obtained a r e s t a t i s t i c a l l y s i g n i f i c a n t and  reproducible.  BIBLIOGRAPHY W a l k e r , W.H., and D i l l , C., T r a n s , Am, E l e c t r o c h e m . S o c , 11 , 153 (1907). Andrews, T., P r o c . I n s t . C i v i l Eng. (1894).  ( B r . ) 118, 356  B a n c r o f t , W. D., Trans. Am. E l e c t r o c h e m . S o c , 33, 79 (1918). Hambuechen, C , B u l l . U n i v . W i s e , E n g . S e r i e s 2, 8, 235 (1900). R i c h a r d s , T. W., and B e h r , J r . , G. E., C a r n e g i e I n s t , of Wash. P u b l i c a t i o n No. 61, (1907), Z F h y s i k . Chem., 58, 301 (1907). B u r g e s s , C. P., Trans. Am. E l e c t r o c h e m . S o c , 1 3 , 17 (1908). M e r i c a , P. D., Chem. Met. Eng., 1 5 , 321 (1916). Mears, R. B., M e t a l P r o g . , 4 8 , 105 (1945). N i k i t i n , L. B., Compt. Rend. Acad. S c i . (U.S.S.R.), 17, 107 (1937); J . Gen. Chem. (U.S.S.R.). i b i d , .9, 794, 975 (1939); i b i d , 1 1 , 146 (1941). Gautam, L. R., and J h a , J . B., P r o c . I n d i a n Acad. S c i . , 18A, 350 ( 1 9 4 3 ) . Endo, H., and Kanazawa, S. K., S c i . R e p o r t s TShoku Imp. U n i v . , 1 20, 124 (1931). Evans, U. R., and Simnad, M. T., P r o c . Roy. S o c , 188A. 372 (1947). Simnad, M. T., and E v a n s , U. R., J . I r o n S t e e l 157. 531 (1947).  Inst.,  G i u l o t t o , L., Nuovo cimento, 1 3 , 220 (1936), D r u e t , Y., and J a c q u e t , P. A., Metaux e t C o r r o s i o n , 22, 139 (1947).  60  (16) Naugle, C. A., A i r Mat. Comm. Tech. R e p t . PT-R1131M>, June, (1947). (17) Thompson, R. P., A e r o . R e s . L a h . R e p o r t , SM 143 ( A u s t . ) Jan.,(1950) (18) Z a r e t s k y , E . M., J . A p p l i e d Chem. (U.S.S.R.), 24, 477 (1951); i b i d , (U.S.S.R.), 24, 687, ( l 9 5 l ) . (19) Akimov, G. V., " P r i n c i p l e s Of C o r r o s i o n Theory and M e t a l P r o t e c t i o n " , p. 145, (1946). (20) Evans, U. R., " M e t a l l i c C o r r o s i o n , P a s s i v i t y , arid P r o t e c t i o n " , p . 587, Edward A r n o l d and Co., London (1946). (21) P r y x e l l , R. E . , and E a c h t r i e b , N. H., J . E l e c t r o c h e m . S o c , 9 9 , 495 (1952). (22) R o s s , T. K., and Thomas, T. H., J . Birmingliam U n i v . Chem. E n g . S o c , 4, 44 (1953). (23) M i n i a t o , 0. K., "Measurement o f S t r e s s P o t e n t i a l s " , M.A.Sc. T h e s i s i n Chem. Eng., U. B. C , (1947). (24) M c D o n n e l l , B., " E f f e c t o f S t r e s s on E l e c t r o l y t i c S o l u t i o n P o t e n t i a l " , M.A.Sc T h e s i s i n Chem. Eng., U. B. C , (1948). (25) J a m i e s o n , R. D . , " S t r a i n P o t e n t i a l s " , B.A.Sc. T h e s i s i n Chem. Eng., U. B. C., (1950). (26) D u d l e y , R. S., "An I n v e s t i g a t i o n o f t h e N a t u r e o f Changes i n E l e c t r o d e P o t e n t i a l Produced b y U n i D i r e c t i o n a l S t r e s s " , M.A.Sc. T h e s i s i n Chem. Eng., U. B. C., (1951). (27) E l l i o t t , R., " S t r a i n P o t e n t i a l s o f Copper Wire i n I . C u p r i c S u l f a t e I I . C u p r i c C h l o r i d e " , M.A.Sc. T h e s i s i n Chem. Eng., U. B. C , (1951). (28) McKeown, J . , and Hudson, 0. P., J . I n s t . M e t a l s , 60, 109 (1937). (29) Harwood, J . J . , C o r r o s i o n , 6, 249, 290 (1950). (30) P a r r e r i , B. A., and T a y l o r , G. I . , P r o c . Roy. S o c , 107A. 422 (1925); T a y l o r , G. I . , arid Quinney, i b i d , 140A. 307 (1934). (31) R o s e n b a i n ,  W., and S t o t t , V. H., i b i d , 14GA, 9 (1933).  61 (32) B o h n e h b l u s h , H. P., and Dewey, P., Trans. Am. S o c . Mech. Eng., 70, 222 (1948). (33) G i b b s , J . W., T r a n s . Conn. Acad., 3, 108 (1875). (34) C a l l e n d a r , L. H., P r o c . Roy. S o c , 115A, 349 (1927). (35) Langmuir, I . , J . Chem. Phys., 1, 1 (1933). (36) G a t t y , 0., and Spooner, E. C. R., "The E l e c t r o d e P o t e n t i a l B e h a v i o r o f C o r r o d i n g M e t a l s i n Aqueous S o l u t i o n " , O x f o r d a t t h e C l a r e n d o n P r e s s , (1938). (37) B a n n i s t e r , L. C , and E v a n s , U. R., J . Chem. S o c , 1361 (1930). (38) Mears, R. B., and Brown, R. H., I n d . E n g . Chem. 33, 1001 (1941). (39) M o r i z e , P., Metaux e t C o r r o s i o n , 22, 71 (1947); Gwathmey, A. T., and Benton, A. P., T r a n s . E l e c t r o c h e m . S o c , 77, 211 (1940); S l a u n e r , R., and G l o c k e r , R., P. E r i s t . , 80, 377 (1940); A n d e r s o n , A. E., J . Am. Chem. S o c , 52, 1000 (1930); Anderson, A. E., N a t u r e , 125. 49 (1929); W a l t o n , C. J . , Trans. E l e c t r o c h e m . S o c , 85, 239 (1944). (40) Mears, R. B., B e l l Lab. R e c o r d , 1 1 , 143 (1933). (41) Newberry, E., J . Am. Chem. S o c , 51, 1315 (1929). (42) P i l l i n g , N. B., and Bedworth, R. E., Chem. Met. Eng., 27, 72 (1922); J . I n s t . M e t a l s , 29, 529 (1923). C o n s t a b l e , P. H., P r o c . Roy. S o c , 115A, 570 (1927); N a t u r e , 123, 569 (1929); Z e i t k n e c h t , , W., E l e c t r o c h e m . , 35, 142 (1929); i b i d . , 36, 16 (1930); P f e i l , L. B., J . I r o n S t e e l I n s t . , 123, 237 (1931); M e h l , R. P., Mc C a n d l e s , E. L., and R h i n e s , P. N., N a t u r e , 134, 1009 (1934); P r e s t o n ,ffi.A., and Bircumshaw, L. L., P h i l . Mag., 20, 706 (1935); W i n t e r b o t t o m , A. B., N a t u r e , 140, 364 (1937); M i l e y , H. A., J . Am. Chem. S o c , 59, 2626 (1927); P r i c e , L. E., and Thomas, G. I . , J . I n s t . M e t a l s , 63, 25 (1933); E v a i s , U. R., and M i l e y , H. A.. N a t u r e , 139, 283 (1937); J . Chem. S o c , 1295, (1937). (43) W i l k i n s , P. J . , P h i l . Mag., 1 1 , 422 (1931). (44) Tamman,' H. L., and K b s t e r , I . J . , Z. anorgan. Chem., 125. 196 (1923).  Lustman, 33., T r a n s . E l e c t r o c h e m . S o c , 8]^, 359 (1942). E v a n s , TJ. R., T r a n s . E l e c t r o c h e m . S o c , 83, 335 (1943), D i g h t o n , A. L., and M i l e y , H . A., Trans. E l e c t r o c h e m . S o c , 8 1 , 321, 391 (1942) Wagner, C , T r a n s . F a r a d a y Soc,, 34 851 (1938). Bengough, G. D., and May, R., J . I n s t . M e t a l s , 32, 108 (1924). Evans, U. R., J". Chem. S o c , 127, 2484  (1925).  E v a n s , TJ. R., " M e t a l l i c C o r r o s i o n , P a s s i v i t y , and P r o t e c t i o n " , Edward A r n o l d and Co., London, (1948). Haase, K., Z. M e t a l l k u n d e , 26, 185 (1934). C a m p b e l l , W. E., and Thomas, U. B., N a t u r e , 142, 253 (1938); Trans. E l e c t r o c h e m . S o c , 76, 303 (1939). Evans, U. R., N a t u r e , 118, 51 (1926). Wagner, C , Z. p h y s i k Chem., ( B ) 2 1 , 25 (1933); i b i d . , (B) 32, 447 (1938); i b i d . , *(B)40» ^ (1938). 4 5  Wagner, C , and Hammen, H., I b i d . , (B) 4 0 , 197 (1938). Hoar, T. P., and P r i c e , L. E., T r a n s . F a r a d a y S o c , 34 , 867 (1938). F r e n k e l , H . , Z. p h y s i k . Chem., (B)26, 117 (1924). S c h o t t k y , E. P., Z. p h y s i k Chem., ( B ) l l , 163 (1930). Evans, TJ. R., J . I n s t . M e t a l s , 30, 239 (1923). P o u r b a i x , M. J . N., "Thermodynamics o f D i l u t e Aqueous S o l u t i o n s " , Edward A r n o l d and Co., London, (1949). (62) Dean, R. B., and D i x o n , W. J . , A n a l . Chem., 2 3 , 636 (1951).  63  APPENDIX  TABLE  I  I  S t r a i n P o t e n t i a l V e r s u s Load ffor S i z e # 2 2 B & S Hard Copper Wire 0 . 0 0 5 N  in  RUN NUMBER  KNOT;  WEIGHT ON LEFT WIRE KGS POUNDS  XJSPi X 1 0  25°  at  C.  POTENTIAL OF LEFT WIRE MINUS 7  POTENTIAL OF RIGHT WIRE (MILLIVOLTS  54  55  58  0 5 10 0 5 10 0 5  59  10 0 5  60  10 0 5  61  62  10 0 5 10 0 5  63  10 0 5 10  0 1.040 2.034  •o 1.040 2.034 0 1.040 2.034 0 1.040 2.034 0 1.040 2.034 0 1.040 2.034 0 1.040 2.034 0 1.040 2.034  - 1 0 . 0 6 - 1 1 . 3 2 - 1 0 . 4 4 + 1.13  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS)  ) 0 - 1 . 2 6 - 0 . 3 8 0 -1.13  +  0.00 1.13  -  4 . 0 0  0  -  6 . 0 0  - 2 . 0 0  -  4 . 0 0 3.50 5.25  0.00 0 -1.25  + + +  3. 4 . 2. 4 .  5 0 5 0  0 0 0 0  +  0 . 0 0  0.00 0 - 1 . 5 0 0.00  0 . 5 0 - 0 . 5 0 + 0 . 5 0 + 8 . 2 5  0 - 1 . 0 0 0.00 0  +  - 2 . 2 5 - 0 . 2 5  6.50  + 8 . 0 0 - 0 . 2 5 - 3 . 2 5 - 1 . 0 0  0 - 3 . 0 0 - 0 . 7 5  TABLE;  II  S t r a i n P o t e n t i a l . V e r s u s Load F o r S i z e #22 B & S S o f t Copper W i r e i n 0.005N KNO Rim NUMBER  WEIGHT ON LEFT WIRE KGS POUNDS IN^  6  7  8:  9  10  11  12  57  70  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  X  io  7  5  a t 25.0° C.  POTENTIAL OF LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) -3.22 -8.63 -17.19  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS ) 0 -5.41 -13.97  - .  - 2.50 - 6.47  _  0 - 3.97 •  '  — '  4- 0.25  - 3.5 -14.25 -17.88 - 2.56 - 6.19 -17.50 -12.75 + 1.78 - 5.19 -12.19 -16.00 - 2.81 -12.44 -17.09 -25.63 - 1.81 - 7.44 -21.32 -20.94 + 0.22 - 6.78 -14.88 -21.88 - 7.13 -17.25 -23.56 -26.75  -  0 - 3.75 -14.50 -18.13 0 -13.63 -14.94 -10.19 0 - 6.97 -13.97 -17.78 0 - 9.63 -14.28 -22.82 0 - 5.63 -19.51 -19.13 0 - 7.00 -15.10 -22.10 0 -10.12 -16.43 -19.62  TABLE I I ( C o n t i n u e d ) 71  72  74  75  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  +11.25 + 6.00 -10.25 -16.13 t 3.16 + 1.47 -14.,50/ -15.38 - 1.32 - 8.81 -18.00 -24.00 -4.68 -14.44 -25.06 -27.50  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  0 - 5.25 -21.50 -27.38 0 - 4.63 -17.66 -18.54 0 - 7.49 -16.68 -22.68 0 - 9.76 -20.38 -22.82  TABLE I I I S t r a i n P o t e n t i a l V e r s u s Load F o r S i z e #22 B & S S o f t Gop-per W i r e i n 0.005N KNO?, a t 40.0° C. RUN MJMBER  46  47  48  WEIGHT ON LEFT WIRE KG-S POUNDS IIP x 1 0 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  7  POTENTIAL OF LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 1.38 -23.38 -23.50 -32.38 - 1.88 -10.35 -23.69 -35.00 - 0.75 - 5.16 -12.63 -24.00  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS 0 -22.00 -22.12 -31.00 0 - 8.47 -21.81 -33.12 0 - 4.41 -11.88 -23.25  TABLE I I I 49  79  80  81  82  83  84  3 •4 5 6 3 4 5 6 3 4 5 6 3 •4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  (Continued +- 1.75 - 5.94 -16.00 -19.00 1.25 - 2.88 -15.00 -23.69 + 4.69 + 0.38 -12.00 -22.25 + 1.94 - 8.00 -17.00 -29.25 -+- 2.69 - 1.13 -13.63 -27.25 +11.19 + 7.44 -10.81 -14.81 + 0.69 - 3.19 -14.56 -28.19  ' 0 -7.69 -17.75 -20.75 0 - 4.13 -16.25 -24.94 0 - 9.94 -16.49 -26.94 0 - 9.94 -.18.94 -31.19 0 -3.82 -16.32 -29.94 0 - 3.75 -22.00 -26.20 0 - 9.88 -15.25 -28.88  TABLE IV S t r a i n P o t e n t i a l V e r s u s Load P o r S i z e #22 B & S S o f t Copper W i r e i n 0.005N KNO* a t 60.0° C. RUN NUMBER  POTENTIAL OF WEIGHT ON LEFT WIRE MINUS LEFT WIRE EGS POUNDS _ POTENTIAL OF 10' RIGHT WIRE IN x (MILLIVOLTS) 3 0.643 - 0.75 4 0.842 -10.32 5 1.040 -21.50 1.239 -25.19 6 2  41  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS) 0 - 9.57 -19.25 -24.44  TABLE 42  43  44  45  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  IV  ( Continued)  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 0.75 -10.32 -21.50 -25.19 - 3.25 -11.94 -21.00 -29.38 + 0.50 - 7.50 -19.38 -40.25 + 2.69 - 5.00 -12.63 -33.00 TABLE  0 - 9.57 -19.25 -24.44 0 - 8.69 -17.75 -26.13 0 - 8.00 -19.88 -40.75 0 - 7.69 -15.32 -35.69  V  S t r a i n P o t e n t i a l V e r s u s Load f o r S i z e #22 B & S S o f t Copper Wirein  ROT NUMBER  0.05N KECK a t 25.0° C.  WEIGHT ON LEFT WIRE KGS POUNDS IN x 10 2  2  3  4  13  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  7  POTENTIAL OP LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 2.28  -•  -21.35 —  - 3.19 - 7.38 -21.66  MAXIMUM STRAIN . POTENTIAL (MILLIVOLTS) 0  -19.07 -  + 0.81 - 0.96 -14.44  0 - 4.19 -18.47 •a 0 - 1.77 -15.25  + 1.00 - 2.25 -17.32 -21.19  0 - 3.25 -18.32 -22.19  —  —  -  68 TABLE 15  16  17  20  64  65  66  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6 3 ^4 5 6  V  (Continued)  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 X e-S 39 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 5.09 - 9.25 -20.56  0 - 4.16 -15.47  - 6.56 -13.81 -25.00  0 - 7.25 -18.44  - 6.13 - 9.56 -21.13  0 3.43 -15.00  +10.75 + 4.44 -10.13 -11.38 - 1.25 - 7.00 -18.19 -23.19 - 2.38 - 5.63 -18.56 -22.50 - 2.13 - 8.13 -19.13 -23.76  0 - 6.31 -20.88 -22.13 0 - 5.75 -16.94 -21.94 0 - 3.25 -16.18 -20.12 0 - 6.19 -17.13 -21.63  •- •  -  - -  -  -  -  TABLE V I S t r a i n P o t e n t i a l V e r s u s Load f o r S i z e #22 B & S S o f t Copper W i r e i n 0.05N ]SN03 a t 40.0° C. RUN NUMBER  50  51  WEIGHT ON LEFT WIRE KGS POUNDS I N ^ x 10? 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  POTENTIAL OF LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 0.56 -21.25 -30.25 -35.13 - 0.69 - 5.41 -23.75 -35.09  MAXIMUM STRAIN . POTENTIAL (MILLIVOLTE 0 -20.69 -29.69 -34.57 0 - 4.72 -23.06 -34.40  TABLE V I ( 52  53  3 4 5 6 3 4 5 6  Continued )  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 2.25 - 9.78 -25.88 -33.75 - 0.25 -11.63 -31.19 - 35.88  0 - 7.53 -23.63 -31.50 0 -11.38 -30.94 -35.63  TABLE V I I S t r a i n P o t e n t i a l V e r s u s Load f o r S i z e #22 B & S S o f t Copper W i r e i n 0.05N KNO3 a t 60.0° C. RUN NUMBER  31  32  33  35  WEIGHT ON LEFT WIRE KGS POUNDS IN^X 1 0 3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  7  POTENTIAL OP LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 0.19 - 8.63 -22.63 -29.50 - 2.50 - 9.69 -18.44 -28.88 - 1.13 - 7.00 -17.13 -28.94 + 3.50 - 1.00 -17.19 -18.88  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS 0 - 7.44 -21.44 -29.31 0 - 5.87 -15.94 -26.38 0 - 5.87 -16.00 -27.81 0 - 4.50 -20.69 -22.38  TABLE V I I I S t r a i n P o t e n t i a l V e r s u s Load f o r S i z e # 2 2 B & S S o f t Copper W i r e i n 0.5N KNOs a t 25° C. 22  23  24  3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  -+- 1.13 - 4.41 -14.50 -27.25 0.00 - 5.25 -13.88 -13.88 - 2.09 - 7.25 -15.16 -13.81  0 - 5,54 -15.63 -28.38 0 - 5.25 -13.88 -13.88 0 - 5.16 -13.07 -11.72  TABLE V I I I 68  69  3 4 5 6 3 4 5 6  (Continued)  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 7.50 -17.13 -24.19 -30.56 - 1.88 . -12.00 -21.81 -27.38  0 - 9.63 -16.69 -23.06 0 -10.12 -19.93 -25.50  TABLE I X S t r a i n P o t e n t i a l V e r s u s Load F o r S i z e #22 B & S S o f t Copper W i r e i n 0.5N K¥0^ a t 40.0° C.  Rim  NUWRFIR  WEIGHT GN LEFT WIRE KGS POUNDS IN x 10 2  25  26  27  28  3 4 5 6 3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  7  POTENTIAL OF LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 4.44 -11.44 -23.44 - 34.56 -. 4.09 - 8.88 -13.06 -20.25 + 0.38 -10.38 -19.32 -27.00 - 3.00 - 7.50 -15.00 -20.00  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS 0 - 7.00 -19.44 -30.12 0 - 4.77 -12.97 -16.16 0 -10.76 -19.70 -27.38 0 - 4.50 -12.00 -17.00  TABLE X S t r a i n P o t e n t i a l V e r s u s Load f o r S i z e #22 B & S S o f t Copper W i r e I n 0.5N KN0-* a t 60.0° C. 29  30  3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 5:^25 -15.93 -20.32  0 -10.68 -15.07 _  - 0.81 -.' 6.56 -17.63 -32.00  0 -.'.5.75 -16.82 -29.19  TABLE X ( C o n t i n u e d ) 37  38  39  3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  - 2.25 - 8.06 -17.50 -27.38 - 1.63 -15.34 -26.69  0 - 5.81 -15.25 -25.13 0 -13.71 -25.06  - 7.00 -13.19 -22.94 -30.50  0 - 6.19 -15.94 -23.50  -  TABLE X I S t r a i n P o t e n t i a l "Versus Load f o r #22 B & S S o f t Copper W i r e i n (D.05N C u S 0 RUN NUMBER  WEIGHT ON LEFT WIRE KGS POUNDS I N x 10? 2  76  77  78  3 4 5 6 3 4 5 6 3 4 5 6  0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239 0.643 0.842 1.040 1.239  4  a t 25.0° C.  POTENTIAL OP LEFT WIRE MINUS POTENTIAL OF RIGHT WIRE (MILLIVOLTS) - 1.38 - 3.00 - 3.94 - 6.00- 1.50 - 2.63 - 4.75 - 4.88 - 0.75 - 1.00 - 2.94 - 5.13  MAXIMUM STRAIN POTENTIAL (MILLIVOLTS.) 0 -1.62 -2.56 -5.62 0 -1.13 -3.25 -3.33 0 -1.13 -1.19 -4.38  TABLE XII.. pH  of  K N O 3  S o l u t i o n s C o n t a c t i n g S i z e #22 B & S S o f t CoppaWire  RUN NUMBER 23 22 24 28 27 29 30 37 38 39 14 63 62 65 66 67 13 64 51 50 33 31 32 61 58 59 60 57 49 46 47 48 44 41 42 45 43  . SOLUTION CONC. TEMP. (N) (°C) 0.50 25 0.50 25 0.50 25 0.50 40 0.50 40 0.50 60 0.50 60 0.50 60 0.50 60 0.50 60 0.05 25 0.05 25 0.05 25 0.05 25 0.05 25 0.05 25 0.05 25 0.05 25 0.05 40 0.05 40 0.05 60 0.05 60 0.05 60 0.005 25 0.005 25 0.005 25 0.005 25 0.005 25 0.005 40 0.005 40 0.005 40 0.005 40 60 0.005 0.005 60 0.005 60 0.005 60 0.005 60  CONTACT TIME (MINS. ) 110 118 160 75 155 70 100 100 110 120 58 90 115 115 125 140 156 165 110 860 80 125 190 90 105 105 115 180 85 110 120 300 95 115 120 220 260  pH  INITIAL 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7  5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 6.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7 5.7  FINAL 5.9 6.0 6.0 6.0 6.0 6.0 6.0 5.8 6.0 5.8 6.0 5.9 5.9 5.9 5.9 6.0 6.0 5.9 6.2 6.4 6.4 6.3 6.3 6.2 6.4 6.3 6.4 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.2 6.5  ! 1 i 11 1 •  IN  Trj f I j r;;  tFT  11  J.L.CJ  i ;i <  !!  ; 1 in t N-i  If-  «  TIT'  l!  1 : 44.  : i .9  I!  I 1 !1 I  "~r: • (•' f  I I  1 1  ! It i1!  1  i1  1 ' /  14*'!  i; ! !  =1 L  ti!  ;  )T.RJ/\|$l l  1  :3 <1 1  !  41  TIT  I !  I t  1  TTTt  felt i ffi'j'C ire if f t yfT ftd J-,-4-  ; 'Phi Jlhiil) ! i  1 -r  if  4 -1  -r-U  1  ...Li i l l  I' 11 I if;: £ 1,1 ' -1 •  .J4J  1  ri 44  1 i-  It  .1  M l  T f t * mi—-r-  1  1 !  11  iM '  -1..  'iTT-TTr~"TTyT  ! "I t t  ! ! i 1  -4-r-  ..f—»  1 •!  LPatMiT  :!  i . t  -U—4-  rrr.,,  JiiJl  1 1  ..4P  » . Li .!  "  Mi!  :  1 1 1 1 «• 1 - : 1 i 1  1 t  50 i; 1  i • ' ! • . ' lit r  T  1  iI  if  •6  u.  I"  • i  -Li 4-r  J—ii. !  4  I  i  f'l  .ic; i4 ; I  M44~  sfafc:  ;i !  'JO''-' <  2  ~i~tr  ±44-  ,|_< _Lu ,i j. —!—j—j—i.  It  11  11  ! t I  1-p  Ah!'  1-  TT7T  pi i  2  Hi!  MiMiiiTliiji ,.i.:ll.iu Ifl:M i  .-U~  7  i i.f • *! j I i  I  1  4.-U  ! i  !'!  '.X.  ^  l-i. I! 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Mi | H  .•i_L  i  Ii : i i  4-X  'I  77  11  Tr  tM  r i-  M.M 'IN;  II : 1  i  ! r  lit:  t M i j- i . M  I  H J-LX.  ill  ! I  !  IT:  MM'  MM  1 •  M I t  Ij ; :j•jj M-l I I I V  i  : M !' ' ' I •I j^7L L J l i i i ^ i X i  i I  i M ; - ] ! iI i 1 j 1 j ' •; i  -V.I  1  1  • in MM I.I \  • i  !M J ! -:ix,J-4..., U-M !  I 'ft  1I-  XX.  II'  1  • ' ' ! i I  -L.LJJ.  i !  i-1  • .i  ..jinii.Mn n h  '  i M  i  i  M  i i  I !;;;;-;, | • " h  I • I  Ii 1 .1 • i  !:Hltlj! .LL-U.J  • I i .  - -M-r-;-T--.-H-< hJ • MM •I i m i MM iI ; i I I .< 1 ;  •ii ii mn  -It  lli: '!,  444  frit  r  i no.  i  1  1 , 141  > HMT  i ! fl  I  ! I !  I 44—  i J  1' 1  -t-f-r r 1  T  I- M I  '! i  TTT T i t i  'Iii  I !•  TJ*ii  •I I  I ! !  1 1 1  • j j M i Ii'"iM .•'MM i 1  t i  M  i:x.4 f ^  I'M lot  I r1  1 T «.t-.l I } -I  1  H  MM  it*  •S* E  11 ii  JJ-  i'4 f  i I  M  • : :  !i  1  PiT-iTtrttimt hii?;;: i - ' H i ij-fim r  Tf:"T  1  t i l Ti 1-. i  !tn  *Fi M I I  ! i-1J-4 "H ;4H- * j--'  r  •l!  i  !'!  l '  I I  1  :  .4 i  1 1 1 !  ru.4  I  i- r •  T~H" dell  4+  jjifc^^' .4-.  • <  4-+  I'M  .1 1  i:  . i' •  '14  U4»W  H—l-  •••I'irifft  I  •  Mle-M Ililii  .'I  I I  ' t  -f  11  I  -4  -4*r  111 v  r  -t'  ii - f p ri.i j  M  11  rt^H4«N--i4  M4  4s  . f f l f f i j ^  ^ f f p t i i  T  1  1  JU-i  1 r4r  T  t  ' l + h & v ^ 1 • T T 1J 1  1  '1 • H i ' M j i i f i n ii 1M i M1 M j l M u 1  h  87  APPENDIX I I The  following section w i l l include  the l o g a r i t h m i c  a method o f how  r a t e i n e q u a t i o n (7.) was a p p l i e d  to the  d e c a y c u r v e s a s measured and p l o t t e d "by t h e Speedomax. I n c l u d e d w i l l h e a d e s c r i p t i o n o f how t h e d e c a y c u r v e s were h a n d l e d , a sample c a l c u l a t i o n arid i n T a b l e s XIv", XV" and XVI the v a l u e s o f t h e c o n s t a n t s so c a l c u l a t e d . The  decay c u r v e s were p l a c e d i n t h e f i r s t  quadrant,  so t h e y would be p o s i t i v e , w i t h t h e o r i g i n a t t h e p o i n t o f maximum s t r a i n p o t e n t i a l .  Integer values of the p o t e n t i a l  were s c a l e d o n t h e c u r v e s u s i n g t h e a x i s e s t a b l i s h e d as t h e r e f e r e n c e .  The t i m e f o r each i n t e g e r  above  value of the  p o t e n t i a l was t h e n measured t o t h e n e a r e s t one h u n d r e d t h o f a minute f r o m t h e zero time a x i s .  The e x p e r i m e n t a l r e l a t i o n -  s h i p between t h e s t r a i n p o t e n t i a l , E , and t h e t i m e , t ,  was  t h e n p l o t t e d o n s e m i - l o g a r i t h m i c paper t o y i e l d a s t r a i g h t l i n e s e c t i o n and two c u r v e d s e c t i o n s , The  one a t each end.  b e s t s t r a i g h t l i n e was g r a p h i c a l l y f i t t e d t o t h e r e l a -  tionship.  The r e s u l t i n g s t r a i g h t l i n e i s now i n t h e f o r m E  =• 2.303 k l o g ( a t + a t ' + l )  (8.)  To s i m p l i f y t h e r e l a t i o n s h i p a s u b s t i t u t i o n was made as follows: set  b = at' + 1  giving  E a 2.303 k l o g ( a t + h)  (9. ) (10.)  88  Now using the c o r r e c t e d experimental v a l u e s of E 5  and t d e t e r m i n e d f r o m t h e b e s t s t r a i g h t l i n e on the p l o t of E v s t , the t h r e e c o n s t a n t s a p p e a r i n g i n e q u a t i o n  (10.)  may be d e t e r m i n e d b y a l g e b r a i c a l l y s o l v i n g t h r e e s i m u l t a neous e q u a t i o n s w i t h t h e c o n s t a n t s as t h e unknowns.  A  sample c a l c u l a t i o n w i l l f o l l o w u s i n g r u n # 36 as t h e  (  example. SAMPLE CALOITLATIOir The e x p e r i m e n t a l r e l a t i o n s h i p between the  strain  p o t e n t i a l and time i s shown i n Tahle X I I I and p l o t t e d F i g u r e 17.  on  M  CO  ^  TABLE X I I I Relationship  Between S t r a i n P o t e n t i a l and Time f o r #22 B & S  S o f t Copper W i r e i n 0.05U KH03 a t 60.0° C. f o r a Load 5 Kilograms E, Strain Potential, mv. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21  t, Time, mine. 0.10 0.15 0.19 0.24 0.31 0.45 0.60 0.76 0.90 1.16 1.40 1.60 2.06 2.60 3.08 3.85 4.50 5.67 7.65 10.50 15.30  Corrected Tiinej, mine.  0.33 0.50 0.75  of  The c o r r e c t e d time v a l u e s a r e now s u b s t i t u t e d i n equation  (10.) as f o l l o w s : 4 - 2.303 k l o g  (0.33 a + b )  (11.)  6 = 2.303 k l o g  (0.50 a + b )  (12.)  8 = 2.303 k l o g  (0.75 a + b )  (13.)  Through the c h o i c e o f E and b y u s i n g a p r o p e r t y of l o g a r i t h m s , i t may be observed  t h a t t h e sum o f e q u a t i o n s  (11.) and (13.) e q u a l t w i c e e q u a t i o n  (12.).  With the loga-  r i t h i m s removed t h i s r e d u c e s t o b as a f u n c t i o n o f a, s i n c e the k w i l l c a n c e l . (0.33 a + b )  The f o l l o w i n g r e l a t i o n s h i p  (0.75 a + b ) - (0.50 a + b )  results: (14.)  2  o r upon m u l t i p l y i n g o u t and s i m p l i f y i n g b = -0.0556 a  (15.)  Removing t h e l o g a r i t h m s f r o m e q u a t i o n s  (11.) and  (12.) and d i v i d i n g ( l l . ) b y (12.) r e s u l t s i n » ( 2?o03 k) a + b ) _ 10 6 (0. 50 a + b 10 2.303 k ( 0 , 33  How s u b s t i t u t e e q u a t i o n  (15.) i n t o e q u a t i o n  0.2844a 0.4444a  _ ~  10  ( 2.303 k )  , (16. )  (16.) t o g e t  (17 ) K L , m }  T a k i n g l o g a r i t h m s o f b o t h s i d e s and c a n c e l l i n g t h e a's on the l e f t hand s i d e g i v e s -0.1938 -  i -2 2.303 k  (18.)  92  or  k = 5.467  (19. )  How knowing b i n terms o f a t i t u t e i n t o e q u a t i o n ( l l . ) t o determine  and t h e v a l u e o f k subsa . Hence, b  and t '  may be r e a d i l y determined f r o m e q u a t i o n s (15. ) and (9.) r e s p ertively  0.2844 a = r ! 0  4 2.303 (5.467)  (20.)  a = 7.3031  (21.)  b = -0.0056  (22.)  t^-0.1377  (23.)  The v a l u e s o f the c o n s t a n t s f o r a p p r o x i m a t e l y 120 d e c a y c u r v e s have been c a l c u l a t e d  and a r e i n c l u d e d  i n the f o l -  lowing Tables.  I n every case, the values of the constants  were s u b s t i t u t e d  i n t o e q u a t i o n ( l l . ) a s a check.  93 TABLE XTV Calculated Values of Constants f o r Logarithmic Section of Decay Curves o f # 22 B & S S o f t Copper Wire i n  J$HO%  Solution  a t 25.0° C. ROT HUHBER  0.005H 6 8 9  10 12 57 70 71 72 74 75 0.05H  2 3 5  13 15 16 19  20  WEIGHT OH LEFT WIRE, Es.  a mv./min •  ZERO TIME  C0HSTAHT, mins.  KHO3 5 5 6 5 •6 5 6 5 6 4 6 4 5 5 6 5 4 5 6 4 5  3.84 4.82 2.99 2.38 1.36 2.97 2.71 3.24 3.24 3.70 1.30 2.55 1.65 5.90 2.52 2.06 1.66 2.42 1.85 1.65 2.44  1.07 1.34 8.84 10.07 4.33 2.15 6.39 18.18 18.18 3.50 5469.68  -0.78 -0.57 -0.17 -0.07 -0.32 -0.52 -0.15 -0.07 -0.07 -0 .2 8  13.30 3.92 27.44 10.32 5.31 12.97 268.29 6.66 82.93  -0.20 -0.02  3.00  -0.00 -0.29  -0.06 -0.16 -0.14 -0.06  -0.00  -0.15  -0.02  KH03 5 5 5 6 4 5 6 5 4 5 5 6 4 5 6  5.98 5.68 6.18  3.22  2.06 4.41 4.72 4.73 1.26 4.64 1.64 5.30 2.78 2.03 3.56  1.23 0.79 7.38 3.07 0.75 7.14 20.18 0.68 1.28" 0.99 1.85 9.28 0.55 57.61 12.86  -0.70 -1.31 -0.13 -0.14 -1.55 -0.18 -0.06 -1.64 -0.70 -0.63 -0.53  -0.12  -1.84 -0.03 -0.05  94 TABLE  64 65 66 67 0.5JT  KHG  21 22 23 24 68 69  XIV ( C o n t i n u e d )  4 5 6 5 6 4 5 6 4 5  0,93 2.33 2.16 2.46 2.35 4.06 4.87 3.06 4.59 5.68  6.75 22.16 51.25 67.67 89.14 21.58 33.19 336.61 11.67 9.51  -0.10 -0.05 -0.02 -0.02 -0.02 -0.05 -0.03 -0.00 -0.08 -0.10  6 4 5 6 5 5 6 4 5 4 5  7.06 1.61 2.78 4.77 3.48 3.48 2.46 3.95 4.40 2.83 4.89  11.25 2.60 12.04 43.89 3.23 2.81 4.02 1.02 4.33 3.32 8.69  -0.13 -0.41 -0.07 -0.03 -0.37 -0.35 -0.30 -0.48 -0.28 -0.23 -0.24  3  TABLE  XV  C a l c u l a t e d V a l u e s o f C o n s t a n t s f o r L o g a r i t h m i c S e c t i o n o f Decay Curves of # 22 B & S S o f t Copper W i r e i n EITOT, S o l u t i o n a t 40.0°( RUN NUMBER  "WEIGHT OH LEFT WIRE,  k  a  mv./min • 0.005N 47 48 49 79 80 81 83 84 *  t  /  ZERO TIME CONSTANT,  mins.  KHO3  5 6 6 5 5 6 5 6 4 5 6 5 6 5 6  2.55 3.64 1.85 1.02 2.50 2.46 2.50 1.28 2.25 3.00 4.58 2.54 3.08 4.01 2.68  9.69 20.34 48.35 756.43 14.18 66.58 16.75 122.47 5.45 13.47 15.63 12.53 86.90 12.18 78.73  -0.11 -0.05 -0.01 -0.00 -0.04 -0.03 -0.06 -0.01 -0.13 -0.06 -0.07 -0.10 -0.15 -0.08 -0.01  95  OjOSH KSO3 5G 51 52 53  4 5 6 4 5 6 4 5  3.00 3.27 4.16 1.14 2.08 2.75 1713 7.56  2.92 1.89 15.32 15.62 439.85 6.47 6.72 5.55  -0.42 -0.52 -0.06 -0.07 -0.02 -0.16 -0.14 -0.16  5 6 5 6 4 5 6 5  5.04 6.95 1.05 1.85 2.18 3.30 4.25 2.23  2.83 13.67 19.98 7.47 12.18 15.57 20.53 4.63  -0.32 -0.06 -0.04 -0.22 -0.13 -0.04 -0.05 -0.25  0.5H 25 26 27 28  TABLE XVI C a l c u l a t e d V a l u e s o f C o n s t a n t s f o r L o g a r i t h m i c S e c t i o n o f Decay Curves of # 22 B & S S o f t Copper W i r e i n KHOS S o l u t i o n a t 60.0°< RUH  KTJMR'RR  0.0053J  WEIGHT 0IT LEET WIRE Kg.  4 5 6 5 6 5 6 5 6 5 6  42 43 44 45  31 32  mv.y^min.  t' ZERO TIMl CONSTANT mins.  K&O3  41  0.05H  a.-  KSTO  2. 01 5.68 6.46 4.87 5.20 3.64 7.45 1.36 6.543 3.34 3.15  2.68 5.59 0.77 0.60 9.54 3.04 0.67 192.46 7.54 1.48 65.38  -0.55 -0.20 -1.21 -1.49 -0.08 -0.31 -1.75 -0.30 -0.10 -0.95 -0.02  10.56 46.84 4.53 1.42  -0.12 -0.02 -0.29 -0.70  3  4 5 5 6  1.62 3.14 3.28 5.17  33 35 36  4 5 6 5 6 5  0.96 3.40 4.59 4.53 4.50 5.47  14.58 6.48 19.38 26.80 5.45 7.30  -0.08 -0.11 -0.07 -0.06 -0.20 -0.14  4 4 5 5 6 4 5 4 5 6  1.84 1.52 2.38 2.51 4.05 3.09 3.51 1.65 2.93 3.82  11.91 4.11 105.20 12.01 4.95 15.47 50.39 5.60 14.12 12.21  -0.13 -0.20 -0.07 -0.08 -0.18 -0.05 -0.02 -0.08 -0.00 -0.09  0.5U KHOs 29 30 37 38 39  -  

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