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UBC Theses and Dissertations

Effect of stress on electrolytic solution potential McDonnell, Basil 1948

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EFFECT OP STRESS ON ELECTROLYTIC SOLUTION POTENTIAL. A t h e s i s submitted i n p a r t i a l f u l f i l m e n t of the requirements f o r the degree of Master of A p p l i e d Science i n Chemical E n g i n e e r i n g . U n i v e r s i t y o f B r i t i s h Columbia Vancouver September, 1948. B a s i l McDonnell EFFECT OF STRESS OH ELECTROLYTIC SOLUTION POTENTIAL. by B a s i l McDonnel l ABSTRACT U r i i - d i r e c t i o n a l s t r e s s e s have been appl ied , t o copper w i r e s , and the p o t e n t i a l d i f f e r e n c e between such w i r e s and u n s t r e s s e d w i r e s determined i n v a r i o u s e l e c t r o l y t e s ! The p o t e n t i a l d i f f e r e n c e s have been determined b o t h by a g a l v a n o -meter" method and p o t e n t i o m e t r i c a l l y ; . The l a t t e r method gave more c o n s i s t e n t r e s u l t s and i s thought t o e l i m i n a t e some o f the p o s s i b i l i t i e s of p o l a r i z a t i o n ; Some c o r r e l a t i o n has been found between the amount of a p p l i e d s t r e s s and the p o t e n t i a l d i f f e r e n c e observed, and thermodynamic arguments have been advanced t o e x p l a i n such r e s u l t s , at l e a s t q u a l i t a t i v e l y . A c o r r e l a t i o n of these same r e s u l t s w i t h time has l e d to the c o n c l u s i o n t h a t the p o t e n t i a l d i f f e r e n c e i s e s s e n t i a l l y due to a s u r f a c e e f f e c t . ACKNOWLEDGEMENT I wish to thank Dr. Seyer and Dr. Shemilt f o r t h e i r suggestions and c r i t i c i s m s . LIST OF CONTENTS Page I I n t r o d u c t i o n . 1. I I Theory. 1. I I I Review o f Previous Observations. 5. IV Apparatus and Experimental Procedures. 11. V R e s u l t s 'of Experiments Galvanometer measurements P o t e n t i o m e t r i c measurements. 14. 18. VI C o n c l u s i o n s . 26. VII References. ''30. VIII Appendix. LIST OF ILLUSTRATIONS F i g u r e . .Page 1. Te s t C e l l . 12. 2. C i r c u i t .diagram. 12. 3,4,5.. E f f e c t o f s t r a i n on g a l v a n i c c u r r e n t s . 16. 6. Change o f p o t e n t i a l w i t h s t r e s s . 20. 7. R e l a t i o n s h i p between e l o n g a t i o n and p o t e n t i a l - t i m e curves. " 20. 8,9. P o t e n t i a l - t i m e curves. 23,24 10. L o g a r i t h m i c r e l a t i o n s h i p between p o t e n t i a l change and time. 25. 11,12. P o t e n t i a l - t i m e curves. . 27,28 Page 1. 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 . I INTRODUCTION. The presence of s t r e s s a f f e c t s the e l e c t r o -chemical c o r r o s i o n of most metals ( 1 ) . S t r e s s may i n f l u e n c e c o r r o s i o n by c r e a t i n g p o t e n t i a l d i f f e r e n c e s between s t r e s s e d and u n s t r e s s e d p a r t s of a m e t a l . These p o t e n t i a l d i f f e r e n c e s can cause l o c a l i z e d a t t a c k by g a l v a n i c c u r r e n t s . To f u r t h e r the understanding of c o r r o s i o n t h i s i n v e s t i g a t i o n t h a t i s r e p o r t e d here was to measure the e f f e c t of s t r e s s on the 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 of copper. Because o f b e a r i n g on the r e s u l t s r e p o r t e d here, the work of other e x p e r i -menters w i l l be o u t l i n e d . But f i r s t the t h e o r e t i c a l b a s i s f o r assuming t h a t s t r e s s changes the p o t e n t i a l of a metal w i l l be d i s c u s s e d . I I THEORY Walker and D i l l (2) suggested t h a t work done on a metal would be a v a i l a b l e as p o t e n t i a l energy, and t h a t work done on a metal e l e c t r o d e i n c r e a s e s the chemical p o t e n t i a l , making the metal more e l e c t r o n e g a t i v e . The European and N.B.S. Convention Page i s used so th a t more e l e c t r o n e g a t i v e means 1. a g r e a t e r tendency f o r the metal to form i o n s 2. the metal i s l e s s noble 3. the metal i s more anodic. When a t e n s i l e f o r c e t h a t i s l e s s than the e l a s t i c s t r e n g t h o f the metal i s a p p l i e d to a metal e l e c t r o d e the work done w i l l be W = 10" 7 T 2 J o u l e s 2Y where W = work done Y = modulus of e l a s t i c i t y T = t e n s i o n i n dynes. SincePgoules are equal to volt-coulombs, i t was suggested by Walker and D i l l (2) and by M i n i a t o (3) that the p o t e n t i a l change would be E = 1 0 " 7 T 2 M v o l t s 2Y^ h P where E = P o t e n t i a l change, v o l t s /j(rho) a d e n s i t y o f the metal, gram/cm 3 M = molecular weight o f the metal h = e q u i v a l e n t s formed per gram-mole when the metal e n t e r s s o l u t i o n P - coulombs/equivalent. Then a t e n s i o n o f 1 kg on 24 B r i t i s h Standard Gauge (S.W.G.) copper wire would produce a p o t e n t i a l change of 2.46 x 1 0 ~ 7 v o l t s . However, i t i s not t h e o r e t i c a l l y p o s s i b l e to a s s o c i a t e I n t e r n a l energy d i r e c t l y w i t h chemical p o t e n t i a l . The r e v e r s i b l e e l e c t r o d e p o t e n t i a l o f a metal can be r e l a t e d to the fre e " e n e r g y . Consider a metal Page 3. M i n a s o l u t i o n o f a s a l t o f the metal as a p a r t o f a r e v e r s i b l e e l e c t r o c h e m i c a l c e l l . I f E i s the s i n g l e e l e c t r o d e p o t e n t i a l and A G i s the change of f r e e energy i n the r e a c t i o n M ^ M * " then - AG B n E F where AG = G^ -** -G^ G}j[ = f r e e energy/gm-mole o f metal Gfl/p" = f r e e energy/gm-mole o f i o n s q u a n t i t y o f e l e c t r i c i t y t h a t passes • through c e l l per gm-mole of i o n formed. So to c a l c u l a t e the change o f the s i n g l e e l e c t r o d e p o t e n t i a l caused by a mechanical f o r c e i t i s necessary to c a l c u l a t e the change o f f r e e energy o f the metal ( A G M ) . When a mechanical f o r c e i s a p p l i e d to the e l e c t r o d e the termodynamic p r o p e r t i e s o f the metal w i l l be a l t e r e d ( 4 ) . Assume t h a t the metal i s homogeneous. L e t the e l e c t r o d e have a u n i f o r m c r o s s - s e c t i o n o f A cm 2 and l e t the l e n g t h be L cms. per gram-mole. Apply a l o n g i t u d i n a l s t r a i n o f f dynes. Then f o r the i s o l a t e d system o f the e l e c t r o d e , c o n s i d e r i n g the process as r e v e r s i b l e , dQ = dU - f dL where dQ, i s the heat e n t e r i n g the system and dU i s the change o f i n t e r n a l energy o f the system. Using the ittormodynamic i d e n t i t i e s Page4. H s U - L f G a H - TS we can w r i t e dG m = - L d f - SdT where H i s t h e r e n t h a l p y , U i s the i n t e r n a l energy, S i s the entropy, T i s the absolute temp-erat u r e and G i s the f r e e energy o f the system. I f the process i s Isothermal, dG M - - L d f . I f i t i s assumed t h a t the l e n g t h remains s u b s t a n t i a l l y constant 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 , A G M = - L ( f df = - L f j o u l e s . _ M To7 K W But L = molecular weight - M ( d e n s i t y ) ( a r e a ) p A So A (hn =• - fM j o u l e s . 10'^ A For the r e a c t i o n M £ M'"«€ ; - AG = nFE when the metal e l e c t r o d e i s u n s t r e s s e d . When the e l e c t r o d e i s s t r e s s e d w i t h a t e n s i o n f , A G and E change so t h a t - A Gf = >iFEf. L e t A E = E f - E be the change o f the s i n g l e e l e c t r o d e p o t e n t i a l caused by the t e n s i o n f . Then A E = -(4G f - A G ) hF But A G - Gj^n - G M A G f = - ( G M - * - A G M ) A G F - A G = - A G M = 4- M f 10 l> A Therefore A E = - _ j l £_ v o l t s . 10'A Page 5,. T h e o r e t i c a l l y the t e n s i o n on the metal makes i t more e l e c t r o p o s i t i v e . A c c o r d i n g to t h i s equation a t e n s i o n o f 1 kg. on a r e v e r s i b l e e l e c t r o d e of 24 S.W.G. copper wire would make the e l e c t r o d e p o t e n t i a l 1.99 mv more e l e c t r o p o s i t i v e . T h i s has not been observed. However Des Coudres (5) v e r i f i e d a s i m i l a r equation w i t h a mercury e l e c t r o d e t h a t was under a p r e s s u r e head. The p r o p e r t i e s o f metals are not s u i t a b l e f o r a simple mathematical treatment o f s t r a i n e f f e c t s such as has been used. In p a r t i c u l a r , metals are u s u a l l y heterogeneous, and accurate c a l c u l a t i o n s become i n v o l v e d and u n c e r t a i n ( 6 ) . A s i n g l e c r y s t a l c o u l d be used (7), but would have o n l y s l i g h t s t r e n g t h . I I I . REVIEW OP PREVIOUS OBSERVATIONS. There have been many o b s e r v a t i o n s and measure-ments o f p o t e n t i a l changes produced by s t r e s s i n g metals; there has been l i t t l e agreement of r e s u l t s . Andrews (8) measured the change of e l e c t r o d e p o t e n t i a l produced i n s t e e l by deformation and found t h a t samples elongated 20^ and p l a c e d i n sodium c h l o r i d e s o l u t i o n were 1 - 1 9 mv. more e l e c t r o n e g a t i v e , the amount depending on the type of s t e e l . Hambuechen (9) 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 up to the y i e l d p o i n t i n f e r r i c c h l o r i d e solutions-*-- Measurements were made by I Page 6. the compensation method. In a l l t e s t s the p o t e n t i a l o f the metal became more e l e c t r o n e g a t i v e . With wrought i r o n samples changes v a r i e d from 0.6 to 29 mv. Walker and D i l l (2) i n r e v i e w i n g Andrew's work showed t h a t the p o t e n t i a l d i f f e r e n c e between s t r a i n e d and u n s t r a i n e d s t e e l i n sodium c h l o r i d e s o l u t i o n s depends upon the method o f h a n d l i n g and the l e n g t h of time i n the s o l u t i o n . In r e v i e w i n g Hambuechen's work they showed t h a t the p o t e n t i a l changes may not have been caused by s t r a i n i n g e f f e c t s s i n c e h i s samples c o u l d not have reached e q u i l i b r i u m w i t h the e l e c t r o l y t e i n the time allowed b e f o r e t e s t i n g . Walker and D i l l t e s t e d s t e e l samples by s t r e s s i n g up to the b r e a k i n g p o i n t In f e r r o u s s u l f a t e s o l u t i o n s and measuring the p o t e n t i a l changes a g a i n s t a calomel c e l l by the p o t e n t i o m e t r i c compensation method. The s u r f a c e of the sample was prepared by p o l i s h i n g w i t h emery. Below the e l a s t i c l i m i t the p o t e n t i a l was changed l i t t l e or not at a l l . Above the e l a s t i c l i m i t the p o t e n t i a l was changed e l e c t r o n e g a t i v e l y under load. When the l o a d was removed the p o t e n t i a l became s l i g h t l y more e l e c t r o p o s i t i v e than i t was i n i t i a l l y . At the b r e a k i n g p o i n t the p o t e n t i a l change was 50 mv. more e l e c t r o n e g a t i v e at the time of b r e a k i n g and w i t h time the p o t e n t i a l changed toward, the i n i t i a l v a l u e . Page 7. Measurements of the e l e c t o d e p o t e n t i a l at s e v e r a l temperatures and measurements o f the temperature of the s t e e l d u r i n g s t r e s s i n g showed t h a t the p o t e n t i a l changes c o u l d not be caused by temperature changes, because the temperature c o e f f i c i e n t under t e s t c o n d i t i o n s was p o s i t i v e and the temperature d i d not f a l l d u r i n g the t e s t s . M ercia (10) s t r e s s e d specimens of annealed brass i n s o l u t i o n s of z i n c and copper s a l t s . The surface of the samples was prepared by p o l i s h i n g w i t h emery and e t c h i n g w i t h n i t r i c a c i d . The p o t e n t i a l changes were measured a g a i n s t a calomel c e l l u s i n g a p o t e n t i o m e t r i c method. A i r was excluded by o i l on the s u r f a c e of the e l e c t r o l y t e . He found t h a t the p o t e n t i a l changed 0.2 mv. more e l e c t r o n e g a t i v e when s t r e s s e d to the e l a s t i c l i m i t , and 1.0 mv. more e l e c t r o n e g a t i v e when s t r e s s e d to the y i e l d p o i n t . The change i n p o t e n t i a l was not permanent. Endo and Kamayana (11) conclude from experiments w i t h v a r i o u s l y prepared i r o n samples In a IN. f e r r o u s s u l f a t e s o l u t i o n that the rougher the s u r f a c e the g r e a t e r the e l e c t r o d e p o t e n t i a l . E l e c t r o l y t i c i r o n , e l e c t r i c a l l y p o l i s h e d , was 12 mv. more e l e c t r o -p o s i t i v e than i r o n as deposited, and 6 mv. more e l e c t r o n e g a t i v e than annealed but u n p o l i s h e d i r o n . Page 8. They a l s o found the e f f e c t o f s l i g h t s t r a i n on p o t e n t i a l u s i n g a s i n g l e c r y s t a l o f i r o n . S t r a i n made the c r y s t a l s l i g h t l y more e l e c t r o p o s i t i v e . They conclude from p o t e n t i a l time curves that the sur f a c e o f the e l e c t r o d e was p a r t i a l l y covered by an i n v i s i b l e f i l m o f Pe ( 0 H ) 2 and F e ( 0 H ) 5 , whose e f f e c t c o u l d not be ev a l u a t e d or e l i m i n a t e d . N i k i t i n (12) measured the changes of e l e c t r o d e p o t e n t i a l s o f samples o f copper, s i l v e r and i r o n d u r i n g deformation i n s o l u t i o n s o f N/lO copper s u l f a t e , N/lO s i l v e r n i t r a t e and N/lO f e r r o u s s u l f a t e r e s p e c t i v e l y . T e s t s were made w i t h the metal to be s t r e s s e d as one e l e c t r o d e o f the c i r c u i t and a small p i e c e o f the same sample as the t e s t specimen as an a u x i l i a r y e l e c t r o d e . I t was shown to be unnecessary to cover the su r f a c e of the e l e c t r o l y t e w i t h o i l . The p o t e n t i a l change i n c r e a s e d w i t h the speed o f t e s t i n g . In a l l t e s t s w i t h copper the p o t e n t i a l became more n e g a t i v e . The maximum change was 7 mv. The p o t e n t i a l o f h a r d copper changed more than the p o t e n t i a l o f s o f t copper. When s t r e s s e d by con-tinuous t e n s i o n t i l l r u p t u r e the copper became a b r u p t l y more e l e c t r o n e g a t i v e at r u p t u r e . A f t e r r u p t u r e the 0 p o t e n t i a l r e t u r n e d toward the i n i t i a l value r a p i d l y at f i r s t and then s l o w l y but d i d not r e a c h i t i n ten hours. I f the copper^eTormed by l o a d was l e f t l o a d e d Page 9. the e l e c t r o d e p o t e n t i a l , a f t e r l i n e a r dimensions o f the sample had ceased to change, began to r e t u r n to the i n i t i a l value, at f i r s t r a p i d l y and then more slowly. The p o t e n t i a l r e t u r n e d toward i n i t i a l values at the same speed whether the samples were loaded or not loaded. Deformation changed the p o t e n t i a l o f s i l v e r a maximum o f 20 mv. p o s i t i v e l y and changed the p o t e n t i a l of i r o n a maximum o f 40 mv. n e g a t i v e l y . N i k i t i n s t a t e s 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 to temperature changes s i n c e copper and i r o n show neg a t i v e p o t e n t i a l changes when deformed and have n e g a t i v e temperature 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 while 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 o f e l e c t r o d e p o t e n t i a l . Gautam and Jiha (13) hung annealed copper wires i n a s o l u t i o n of copper s u l f a t e and observed the change i n the p o t e n t i a l d i f f e r e n c e between the w i r e s when weights were added to one o f them. The wires were annealed by h e a t i n g t i l l r e d hot and then d i p p i n g i n methyl a l c o h o l . Measurements were made w i t h a potentiometer. In s o l u t i o n s of N/250 and N/25 copper s u l f a t e , the maximum changes were 6.7 mv. and 2.4 i r -r e s p e c t i v e l y . The s t r a i n e d wire always became more e l e c t r o p o s i t i v e . A f t e r a l o a d of about 1500 kg/sq. cm. Page 10. had been added the p o t e n t i a l d i f f e r e n c e was n e a r l y constant to the maximum l o a d o f about 1800 kg/sq. cm. When the l o a d was removed the s t r a i n e d wire d i d not r e a c h i t s o r i g i n a l v a l u e . Evans (14) measured the change of p o t e n t i a l w i t h time o f samples o f m i l d s t e e l i n a s o l u t i o n o f N/lO KCl underjsteady s t r e s s . At any time compres-s i v e s t r e s s e s gave more e l e c t r o p o s i t i v e p o t e n t i a l s , and t e n s i l e s t r e s s e s 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 s , than when the t e s t area was not s t r e s s e d . The same f i n a l p o t e n t i a l was reached whether the t e s t area was compressed, extended, not s t r e s s e d , or s u b j e c t to a l t e r n a t i n g s t r e s s . MIniato (3) hung p a i r s o f w i r es i n s o l u t i o n s and added weights to one wire to observe the e f f e c t o f s t r e s s on p o t e n t i a l . A galvanometer was used to measure p o t e n t i a l d i f f e r e n c e s between the t e s t wires. S t r e s s changed the p o t e n t i a l of copper, b r a s s and s t e e l wire i n 4$ sodium c h l o r i d e n e g a t i v e l y . Gen-e r a l l y the p o t e n t i a l changed l i n e a r l y w i t h stress, to near the y i e l d p o i n t where the p o t e n t i a l d i f f e r e n c e between the wires became constant. The maximum changes o f p o t e n t i a l as i n d i c a t e d by galvanometer d e f l e c t i o n s were 1.45 mv. f o r c o l d drawn copper under 2700 kg/sq. cm. s t r e s s , 0.5 mv. f o r annealed copper under 400 kg/sq. cm. s t r e s s , 1 . 7 5 mv. f o r b r a s s under Page 11. 22C0kg/sq. cm. s t r e s s , and 10 mv. f o r s t e e l under 2400 kg/sq. cm. s t r e s s . S t r e s s i n g c o l d drawn copper wires i n sodium s u l f a t e and sodium carbonate gave no galvanometer d e f l e c t i o n s . ' Potassium c h l o r i d e s o l u t i o n s gave s i m i l a r r e s u l t s to sodium c h l o r i d e s o l u t i o n s . In s o l u t i o n s of c u p r i c c h l o r i d e , ammonium c h l o r i d e , and a c i d i c and a l k a l i n e sodium c h l o r i d e , the i n i t i a l p o t e n t i a l d i f f e r e n c e s between copper wires produced o f f - s c a l e d e f l e c t i o n s . IV. APPARATUS AND EXPERIMENTAL PROCEDURES. Samples o f wire to be t e s t e d were p l a c e d i n c e l l s l i k e t h a t shown i n F i g u r e 1. The wires were suspended from hooks i n the top bar of a four f o o t square 4 by 4 wooden frame. Scale pans were atta c h e d to the w i r e s below the c e l l s to which weights c o u l d be added to s t r e s s the w i r e s . The wires were i n s u l a t e d from the hooks and pans by b a k e l i t e . E l e c t r i c a l con-n e c t i o n s were made to the wires by screw f a s t e n i n g s and by s p r i n g c l i p s which gave good e l e c t r i c a l c o n t a c t between the t e s t w i r es and the l e a d w i r e s . Measurements were made w i t h a galvanometer, w i t h a s e n s i t i v i t y o f 0.295 mv./cm. s c a l e r e a d i n g , and w i t h a Leeds and Northrup K-2 type potentiometer. These instruments were connected to - the c e l l s i n the way shown i n F i g u r e 2. Tast Wires Electrolyte Rubber plug Rubbe r stoppt I 80 mm P y r e x tubing Stop-cock grease 10 mm Pyrcx tubing F I G U R E 1. T z s t C t l l in S e c t i o n "to get./tr~a.no/77eter o n Potentiometer "to Galvanometer to test cells "to e/rrf on Potentiometer Externa.! Resistance FIGURE 2. Circuit Diagram Page 15. The w i r e s . t o be t e s t e d were f i r s t cleaned w i t h e t h y l e t h e r . They were then coated w i t h a t h i n l a y e r of p a r a f f i n wax above and below the s e c t i o n to be exposed to the e l e c t r o l y t e and p l a c e d i n the c e l l w i t h w i t h s u f f i c i e n t weight suspended to prevent c u r l i n g . The s e c t i o n exposed was about one centemeter l o n g . Then the e l e c t r o l y t e was poured i n the c e l l . I n those t e s t s u s i n g a deareated e l e c t r o l y t e , the su r f a c e o f the e l e c t r o l y t e was covered w i t h a l a y e r o f Stanolax, a petroleum o i l , one centimeter deep. The e l e c t r o l y t e s were prepared u s i n g d i s t i l l e d water. When r e q u i r e d the e l e c t r o l y t e s were deareated by b o i l i n g or by p l a c i n g under a vacuum o f 65 cms. o f mercury. In t e s t s by M i n i a t o ' s method the l e a d w i res from the c e l l were connected to the galvanometer. The g a l v a n i c c u r r e n t i n the c e l l was shown by the de-f l e c t i o n o f the galvanometer-mirror's image on the galvanometer s c a l e . The c i r c u i t was arranged so t h a t a r e s i s t a n c e o f 10,000 or 20,000 ohms c o u l d be i n s e r t e d to reduce i n i t i a l c u r r e n t s t h a t might produce o f f - s c a l e d e f l e c t i o n s . Weights were added to the s c a l e pan on one o f the wires and the e f f e c t o f s t r a i n i n g t h i s wire on the c u r r e n t i n the c e l l was found by r e a d i n g the d e f l e c t i o n o f the image on the Page 14. s c a l e . Since the c u r r e n t i s caused by p o t e n t i a l ' d i f f e r e n c e s between two w i r e s , changes i n the c u r r e n t may i n d i c a t e changes i n the p o t e n t i a l d i f f e r e n c e ] and so the change i n the e l e c t r o d e p o t e n t i a l s of the s t r a i n e d w i r e . In p o t e n t i o m e t r i c t e s t s the l e a d w i res from the c e l l were connected to the potentiometer. The p o t e n t i a l d i f f e r e n c e between the two w i r e s i n the t e s t c e l l was thus measured a g a i n s t a standard West cam c e l l . Weights were added to the s c a l e pan on one of the wires and the e f f e c t o f s t r a i n i n g t h i s wire on the p o t e n t i a l d i f f e r e n c e between the two wires was observed by a d j u s t i n g the potentiometer to o b t a i n a balance o f the p o t e n t i a l s i n the c i r c u i t , and then r e a d i n g the potentiometer s c a l e . To measure the e x t e n s i o n o f a wire marks on the wire, above and below the c e l l y were observed through the two t e l e s c o p e s o f a cathetometer capable o f measuring 0.001 cm. V. RESULTS O P EXPERIMENTS. Galvanometer Measurements. The use of a galvanometer to i n d i c a t e the changes i n e l e c t r o d e p t o e n t i a l produced by s t r a i n was not a l t o g e t h e r s u c c e s s f u l . The p r i n c i p l e d i f f i c u l t y was t h a t the m i r r o r image s h i f t e d c o n t i n u o u s l y , showing Page 15. that the c u r r e n t was not steady. Since M i n i a t o (3) had been s u c c e s s f u l i n o b t a i n i n g steady, c o n d i t i o n s many t e s t s were made, but these and correspondence w i t h M i n i a t o , f a i l e d to show the reason f o r l a c k o f agreement. Tests were made on the wi r e s that are l i s t e d as f o l l o w s . 5 p a i r s o f s o f t drawn 14 S.W.G. copper wire 5 " " c o l d drawn 14 S.W.G. " " 7 " " s o f t drawn 18 S.W.G. " " 12 " 11 c o l d drawn 21 S.W.G. " " 7 " " c o l d drawn 24 S.W.G. " " The r e s u l t s may be summarized as f o l l o w s . 1. The i n i t i a l p o t e n t i a l d i f f e r e n c e between two app a r e n t l y s i m i l a r w i r e s was sometimes as l a r g e as 20 mv. 2. By v a r y i n g the r e s i s t a n c e o f the c i r c u i t i t was found t h a t the apparent p o t e n t i a l d i f f e r e n c e depended upon the c u r r e n t . Large d e f l e c t i o n s c o u l d be reduced s h o r t i n g the t e s t w i r e s . This i n d i c a t e d p o l a r i z a t i o n . 3. R e p o r t i n g o n l y those t e s t s o f l o a d i n g and un-l o a d i n g the wires which i n d i c a t e d some c o n s i s t e n c y , there were 48 t e s t s showing no s t r a i n e f f e c t s , 9 t e s t s i n d i c a t i n g e l e c t r o n e g a t i v e p o t e n t i a l changes due to s t r a i n , 8 t e s t s i n d i c a t i n g e l e c t r o p o s i t i v e p o t e n t i a l changes due to s t r a i n , and 2 t e s t s i n d i c a t i n g e l e c t r o p o s i t i v e p o t e n t i a l changes f o r small s t r a i n s and e l e c t r o n e g a t i v e p o t e n t i a l changes f o r l a r g e s t r a i n s . The r e s u l t s and c o n d i t i o n s o f three t e s t s which showed a s t r a i n e f f e c t are t a b u l a t e d i n Table 1. (See appendix) and p l o t t e d i n F i g u r e s 3, 4 and 5.-«- These t e s t s are i n c l u d e d to show the method used to determine the e f f e c t o f s t r e s s i n g the w i r e s . They are not Page H.7. t y p i c a l o f the ge n e r a l r e s u l t s because i n these the c u r r e n t s are f a i r l y steady and because the s t r a i n e f f e c t c o u l d be r e p e a t e d s e v e r a l times. I n F i g u r e 3 d u r i n g the time i n t e r v a l 1.5 to 4.25 minutes a s t r e s s o f 190 kg/sq. cm. on the ne g a t i v e wire reduced the c u r r e n t , seemingly i n d i c a t i n g t h a t the s t r a i n e d wire had become more e l e c t r o p o s i t i v e . In the time i n t e r v a l 5.25 to 6.75 minutes a s t r e s s o f 390 kg/sq. cm. i n c r e a s e d the c u r r e n t , i n d i c a t i n g t h a t the s t r a i n e d wire had become more n e g a t i v e . I n F i g u r e 3 small s t r e s s e s seemed to change the e l e c t r o d e p o t e n t i a l o f the s t r a i n e d wire p o s i t i v e l y , and l a r g e s t r e s s e s n e g a t i v e l y . I n F i g u r e 4 and 5 the e l e c t r o d e p o t e n t i a l s o f the w i r e s seemed to become more e l e c t r o -p o s i t i v e w i t h s t r a i n . For example, i n F i g u r e 5 i n the time i n t e r v a l 3 to 4 minutes, a s t r e s s o f 550 kg/sq. cm. on the p o s i t i v e wire i n c r e a s e d the c u r r e n t , i n d i c a t i n g t h a t the wire had become more e l e c t r o p o s i t i v e . System o f numbering t e s t s . Example, 21 Cu cd 6. Th i s means the s i x t h t e s t w i t h a p a i r o f c o l d drawn 21 S.W.G. copper, w i r e . "sd" stands f o r s o f t drawn wire and "a" stands f o r annealed w i r e . Page 18. . The d i f f e r e n c e s between the r e s u l t s I n F i g u r e 3 and those i n F i g u r e 4 and 5 cannot be a t t r i b u t e d to d i f f e r e n c e s o f s o l u t i o n . T h i s was found from the r e s u l t s o f other t e s t s . Q u a n t i t a t i v e estimates o f the change o f p o t e n t i a l c o u l d not be made because the c u r r e n t d i d not depend s o l e l y on the p o t e n t i a l d i f f e r e n c e between the wires. The r e s i s t e n c e i n the c i r c u i t c o u l d be determined e a s i l y but the degree o f p o l a r i z a t i o n depended upon the c u r r e n t and was d i f f i c u l t to evaluate because the c u r r e n t was always changing. The e f f e c t o f • p o l a r i z a t i o n was l a r g e . For example, i n a t e s t w i t h 21 S.W.G. c o l d drawn copper wire i n 4% sodium c h l o r i d e the p o t e n t i a l d i f f e r e n c e one hour a f t e r f i l l i n g the c e l l was 5.5 mv. as found by the potentiometer w i t h no c u r r e n t f l o w i n g and 0.02 mv. as i n d i c a t e d by the -7 IR drop w i t h a c u r r e n t o f 1.4 x 10 amps. Other causes than the change o f e l e c t r o d e p o t e n t i a l may change the c u r r e n t f l o w i n g i n the c e l l when one of the wires i s s t r a i n e d . I f there i s a f i l m o f c o r r o s i o n products on the s u r f a c e o f the metal changes i n c u r r e n t c o u l d be caused by changes o f the r e s i s t e n c e o f the f i l m by d i s t o r t i o n . P o t e n t i o m e t r i c Measurements. For p o t e n t i o m e t r i c measurements o f the p o t e n t i a l Page 19. change produced by s t r e s s most o f the wires t e s t e d were annealed. Two methods o f an n e a l i n g were f o l l o w e d . I n the f i r s t , t h a t used by Gautam and J h a (13), the s e c t i o n o f the c o l d drawn wire to be t e s t e d was heated to redness i n a bunsen flame and quenched i n methyl a l c o h o l . I n the secdnd method, the w i r e s were heated to about 400° C. i n an atmosphere o f n i t r o g e n by an e l e c t r i c furnace, kept at t h i s approximate temperature f o r 20 to 30 minutes and cooled, s t i l l i n n i t r o g e n . Both methods o f anne a l i n g gave the same apparent r e s u l t when t e s t e d . No d i f f e r e n c e i n behavior was observed between u s i n g a r e a t e d and deareated e l e c t r o l y t e s . T ests were made on the wires that are l i s t e d as f o l l o w s . 31 p a i r s o f annealed 24 S.W.G. copper wire 4 " " c o l d drawn 24 S.W.G. copper wire 20 " " annealed 21 S.W.G. " " 3 " " c o l d drawn 21 S.W.G. " 11 2 " " annealed 14 S.W.G. " " In Table I I (see appendix) and i n F i g u r e 6 are some t y p i c a l r e s u l t s showing the p o t e n t i a l changes produced by adding weights q u i c k l y to one wi r e . One p o t e n t i a l r e a d i n g was taken a f t e r each i n c r e a s e o f s t r e s s . Weights were added as r a p i d l y as re a d i n g s c o u l d be taken. The l e n g t h o f these t e s t s was about Page 21. f i v e minutes (see Table I I ) . These r e s u l t s compare w i t h those o f Guatam and Sha i n magnitude, but are e l e c t r o n e g a t i v e p o t e n t i a l changes, whereas t h e i r p o t e n t i a l changes were e l e c t r o p o s i t i v e . No r eason f o r t h i s c o n t r a d i c t i o n has y e t been' found. There was a s l i g h t l y g r e a t e r p o t e n t i a l change i n d i l u t e s o l u t i o n s . Compare curves 1 and 4 w i t h curves 3 and 2. Gautam and 3>ha a l s o observed t h i s . Comparison o f curve 5 to curve 4, F i g u r e 6, shows t h a t a g r e a t e r l o a d i s r e q u i r e d to produce a p a r t i c u l a r change of p o t e n t i a l at the second l o a d i n g (curve 5) than i s r e q u i r e d at the f i r s t l o a d i n g (curve 4 ) . A g r e a t e r s t r e s s i s r e q u i r e d to elongate the wire a f t e r i t has been s t r a i n e d than when i t i s f r e s h l y annealed. I t w i l l be shown t h a t the p o t e n t i a l e f f e c t s are r e l a t e d to e l o n g a t i o n . I f the weights were added i n t e r m i t t e n t l y so t h a t s e v e r a l p o t e n t i a l r e a d i n g s c o u l d be taken between a d d i t i o n s , r e s u l t s were o b t a i n e d l i k e those g i v e n i n Tables IV and V (see appendix) and p l o t t e d i n F i g u r e s 8 and 9. These curves show the tendency o f the p o t e n t i a l change produced by s t r a i n i n g to drop toward zero as time passes. Note i n these curves that the removal o f the l o a d causes l i t t l e or no change i n the p o t e n t i a l . Page 22. Fi g u r e 7 (Table I I I ) compares percent e l o n g a t i o n and the p o t e n t i a l - time r e l a t i o n s h i p f o l l o w i n g s t r e s s e s on c o l d drawn and on annealed copper. The g r e a t e r e l o n g a t i o n w i t h annealed copper g i v e s a g r e a t e r s t r a i n p o t e n t i a l e f f e c t . S e c t i o n s A and B o f the curves i n F i g u r e 8, and s e c t i o n s C, D and E o f the curves i n F i g u r e 9, are p l o t t e d i n F i g u r e 10 showing t h a t the r e l a t i o n s h i p between the p o t e n t i a l change f o l l o w i n g deformation and the time el a p s e d i s approximately l o g a r i t h m i c i n some t e s t s . An e x p l a n a t i o n o f these e f f e c t s i s t h a t copper, when p l a c e d i n con t a c t w i t h an e l e c t r o l y t e , does not rea c h a steady s t a t e w i t h the e l e c t r o l y t e immediately. The p o t e n t i a l may change d u r i n g the fo r m a t i o n o f some surf a c e f i l m . The p o t e n t i a l w i l l be steady when the f i l m i s completely formed. Then i f copper i s elongated f r e s h s u r f a c e may be exposed and the p o t e n t i a l w i l l change q u i c k l y toward the o r i g i n a l value, and w i l l r e t u r n w i t h time to the steady s t a t e p o t e n t i a l as the breaks i n the f i l m r e p a i r . Thus i n F i g u r e 7 the g r e a t e r e l o n g a t i o n o f annealed copper may have broken the s u r f a c e f i l m more completely and so g i v e n the gr e a t e r s t r a i n ^ p o t e n t i a l e f f e c t . £ 3 Page 26. The r e s u l t s p l o t t e d i n F i g u r e 11 and F i g u r e 12 (Table VI) show th a t d i f f e r e n t s o l u t i o n s give markedly p o t e n t i a l - t i m e curves. I t has been shown (15) t h a t the magnitude o f the steady s t a t e p o t e n t i a l depends upon the a c i d i t y and s a l i l i n i t y o f the e l e c t r o l y t e . I t was a l s o found that i f a wire was s t r e s s e d immediately a f t e r the a d d i t i o n o f the e l e c t r o l y t e no s t r a i n p o t e n t i a l change was produced. P o s s i b l y the f i l m was not then formed. In these experiments no i n c r e a s e was observed in the i n i t i a l p o t e n t i a l d i f f e r e n c e between a p a i r o f annealed w i r e s , u s u a l l y l e s s than 2 mv., when one of the w i r e s was s t r a i n e d b e f o r e the a d d i t i o n o f the e l e c t r o l y t e . Newberry ( 1 6 ) t r e a t e d copper i n s e v e r a l d r a s t i c a l l y d i f f e r e n t ways but no d i f f e r e n c e i n the I n i t i a l p o t e n t i a l was observed that c o u l d be a t t r i b u t e d to mechanical c o n d i t i o n s . "On the other hand the nature of the s u r f a c e c e r t a i n l y a f f e c t s the speed of the r e a c t i o n which occurs between the e l e c t r o d e and the e l e c t r o l y t e . " VI. CONCLUSIONS. The measurements made w i t h a galvanometer show how g a l v a n i c c u r r e n t s are reduced by p o l a r i z a t i o n . I t i s not p o s s i b l e from the experiments r e p o r t e d here 2,7 •|.. - • _ i ,J. ;-(+ .III? _' 1 73f 3.;h j ivr 7L7J7- " ;-7-i-7" •7~7 rr— .. i7'!7 m~;— r - • j ii.'. r| : ; • -••' a:- ¥ 1 ©7y II, -•"7 - •* f-' _r±r7 • t-j- . .J 77'7f\ -• ,4 -'- Irp. A:A t •.777 ''.it1': P E N ill •rtH: I E k s ...i • a.tj-' <: 71*^  A 7t7 - .^-J. : ,7 : Art .... •7.. _ 1.' 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' 1 ;-VJ 6 ri 1 o • l i ^ : .7 t i 'i: ._/ . f\7 Mi aft •«<f' ft' F . L! • • ! • • V- 'V r • - •:.b ?;•}••. ' !TJ"TT . :c_v 7'7' - f - i - r ^ - I A. r T77r 7 yA± •K-,1--7-r -crfci •'•:i; "•".4". lit: r-t r , • "> ' • «J 7 T rr.;'.'; : • ; - , - : " J " - i~ * .]"•.}'. ' T ; „ : '7. ;1 L .7rA A: :!7777 ' 17u. 7 I u JO>: M £ -•• '-'/ 'v -••••' f ;- lit' I_ "-' - ; L $77 •77T t'A~: AA- il7:. . tir 77r. " ! •' .A. c-o ic - -ri:. -, ••} ->±/ . -• ,.,P •7.1 *Ct J. . 26 Is. In: 19<• ; v s 34 7:1'--7, : iA x. • • *i i~ ' ' rt'i R 1* '-J - V . ,""[-"-1 LT' ."A m 7 t - •:6. it* # r J- - r :;i.rt. i • til \l 7v" - r p f V T". . . . C-- "I*C. 7 /!->-7 p "7: i" :-7f 7- 71*7' H -J*"J— A;' -""i-jT* '771 77 r , f e . • [r -T P - :r ; i : \ : rj-V'- "('.. (• : rA- 7.7' : : , ; -.-4-:--7'TLX J711*7". 477" : 77 '-74-77 """_*•._: I i -T.7 Z: i * • : \ " xl_:" J -> : / : ^ - .; 7 17. -7 ':rx: 7±P pp. l-'-lT. • IUT ES >•;••. 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T;4 \ Page 29. to make any c o n c l u s i o n as to the e f f e c t o f s t r a i n upon the 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 o f copper. The measurements made w i t h a potentiometer are summarized as f o l l o w s . 1. The d i r e c t i o n and magnitude of the p o t e n t i a l change produced hy s t r a i n i n g copper depends upon the e l e c t r o -l y t e . A c c o r d i n g to the theory i f s t r a i n o n l y a f f e c t s the 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 o f the metal, the nature o f the s o l u t i o n should have no i n f l u e n c e . 2. S t r a i n d i d not a p p r e c i a b l y i n f l u e n c e the 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 o f copper u n l e s s accompanied by e l o n g a t i o n . T h i s i n d i c a t e s t h a t the p o t e n t i a l changes produced by s t r e s s i n g were s u r f a c e e f f e c t s . 3. The magnitude o f the p o t e n t i a l change produced by s t r e s s i n g copper wire i n copper, s u l f a t e s o l u t i o n s was a l o g a r i t h m i c r e l a t i o n s h i p to time. T h i s a l s o i n d i c a t e s t h a t the p o t e n t i a l changes were s u r f a c e e f f e c t s . The p o t e n t i a l may depend upon the regrowth o f a f i l m on the f r e s h s u r f a c e s exposed by e l o n g a t i o n o f the me t a l . I t might be supposed the growth o f a f i l m would be a c c o r d i n g to a p a r a b o l i c e quation but many metals o x i d i z e a c c o r d i n g to a l o g a r i t h m i c e q uation (17). 4. 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 not occur u n l e s s the copper 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. 5. Removal o f the l o a d caused l i t t l e change i n the p o t e n t i a l . Annealed copper I s i n e l a s t i c (18) and so the wire that had been s t r e s s e d d i d not r e t u r n to i t s o r i g i n a l l e n g t h . So the removal o f the l o a d d i d not much a l t e r the c o n d i t i o n s at the sur f a c e o f the wire t h a t c o n t r o l l e d the p o t e n t i a l change. The o r i g i n a l i n t e n t i o n o f measuring the e f f e c t o f s t r e s s on the 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 o f copper and a p p l y i n g the r e s u l t s to a t h e o r e t i c a l e q u a t i o n has not been f u l f i l l e d . The s t r a i n p o t e n t i a l Page 30. changes reporte d here and by others are p r i m a r i l y surface phenomena. The c o n d i t i o n of s t r a i n on the metal electrode has l i t t l e i n f l u e n c e on the electro d e p o t e n t i a l . To make measurements that can be i n t e r -preted the com p l i c a t i n g e f f e c t s of the surface f i l m must be avoided. On the subject of s t r a i n p o t e n t i a l s Copson, w r i t e s (19) : " I t i s f r e q u e n t l y s t a t e d t h a t energy st o r e d i n a d i s t o r t e d metal makes such metal more e l e c t r o -negative than ........ s t r e s s - f r e e m a t e r i a l , and that as a r e s u l t g a l v a n i c e f f e c t s may cause r a p i d c o r r o s i o n of the d i s t o r t e d metal. Attempts have been made to t a r r i v e at the p o t e n t i a l d i f f e r e n c e . Results vary but i n general i n d i c a t e o t h a t the d i f f e r e n c e i n emf. i s only a few my. This d i f f e r e n c e i s too small to have much e f f e c t on c o r r o s i o n and could e a s i l y be upset by such f a c t o r s as con c e n t r a t i o n c e l l s . " v I t i s p o s s i b l e that w h i l e the st a t e of s t r a i n on a metal has l i t t l e i n f l u e n c e on the ele c t r o d e p o t e n t i a l , the increased i n t e r n a l energy of the s t r a i n e d metal (20) may c o n t r i b u t e to the energy necessary f o r a c t i v a t i o n of the r e a c t i o n s i n v o l v e d i n corrosion^ and thus s t r a i n may speed c o r r o s i o n . VI I . REFERENCES. 1. E.H. Dix J r . A c c e l e r a t i o n of the r a t e of c o r r o s i o n Page 31. by h i g h constant s t r e s s e s . Am. I n s t . Mining Met. Eng., Met. Div., Tech. Pub. No. 1204, 30 pp (19#0). J.T. Waber, H.J. McDonald and B. Longten. Trans. Am. Electrochem. S o c , 87,209 (1945). 2. Walker and D i l l . E f f e c t o f s t r e s s upon the el e c t r o m o t i v e f o r c e o f s o f t i r o n . Trans. Am. E l e c t r o -chem., S o c , 61,153 (1907). 3. O.K. M i n i a t o . 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., Univ. o f B.C. (1947). 4. P.W. Bridgeman. A Condensed C o l l e c t i o n o f "Thermo-dynamic Formulas, P. 31. Cambridge Harvard Univ. Press (1925). 5. Des Coudres. Weid ann., 46,292 (1892). 6. R.W. Goranson. P h y s i c s o f s t r e s s e d s o l i d s . J . Chem. Phys., 8,323 (1940). 7. A.T. Givathmey and A.F. Benton. Growth, o r i e n t a -t i o n and p r e p a r a t i o n o f s i n g l e c r y s t a l s o f copper. J . Phys. Che., 44,35 (1940). 8. Andrews. Proc. I n s t . C i v i l Eng. ( B r . ) , 118, 356 (1894). 9. Hambuechen. B u l l . Univ. Wise. Eng. S e r i e s , 2, No. 8, (1900). 10. P.D. Me r c i a . Met. Chem. Eng. 15,321 (1916). 11. H. Endo and S. Kamayana. S i n g l e p o t e n t i a l s o f I r o n and s t e e l e l e c t r o d e s . S e i . Reports Tohoku Univ.., 20,124 (1931). 12. L.V. N i k i t i n . E l e c t r o c h e m i c a l method f o r the study o f mechanical deformation o f metals. Compt. rend, acad. s c i . U.S.S.R., 17,107 (1937). Change o f e l e c t r o d e p o t e n t i a l s o f metals d u r i n g t h e i r mechanical deform-a t i o n ( I ) . J . Gen. Chem. (U.S.S.R.), ; 9,794 (1939 ). The temperature c o e f f i c i e n t o f the e l e c t r o d e p o t e n t i a l o f i r o n . J . Gen. Chem. (U.S.S.R.), 11,146 (1941). 13. L a j j a Ram Gautam and J.B. $ha. E l e c t r o l y t i c s o l u t i o n p r essure o f copper wires under s t r a i n . Proc. I n d i a n Acad. S c i . , 18A,350 (1943). ° . Page 32. 14. U.K. Evans and M. T c h o r a l d j i Simchfad. Mechanism o f c o r r o s i o n f a t i g u e o f m i l d s t e e l . Proc. Roy. Soc. (London), 188A,372 (1946-47). 15. L.C. B a n n i s t e r and U.R. Evans. P o t e n t i a l time curves o f some i r o n a l l o y s . J . Chem. S o c , 1361(1930). P. Vies and A. Ago. Some p r o p e r t i e s o f the e l e c t r o -motive f o r c e s developed by c o n t a c t o f metals w i t h s o l u t i o n s o f v a r i o u s a c i d s and s a l t c o n c e n t r a t i o n s . Compt. rend., 188,1550 (1929). G.V. Akinov and I.L. R o z e n f e l d . I n f l u e n c e o f the p H of a s o l u t i o n on the c o r r o s i o n and e l e c t r o d e p o t e n t i a l o f copper. J . Phys. Chem. (U.S.S.R.), 14,1486 (1940). 16. Edgar Newberry. S i n g l e p o t e n t i a l o f the copper e l e c t r o d e . J . Am. Chem. S o c , 51,1315 (1929). 17. H.A. M i l e y . Fundamentals o f O x i d a t i o n and T a r n i s h . In C o r r o s i o n Handbook, ed. by H.H. U h l i g . John W i l e y and Sons, Inc., New York (1948). 18. J . McKeown and O.F. Hudson. S t r e s s s t r a i n c h a r a c t e r i s t i c s o f copper s i l v e r and g o l d . J . I n s t . Metals, 60, Adv. Copy No. 754, 22 pp (1937). 19. H.R. Copson. E f f e c t o f s t a t i c s t r e s s on g e n e r a l c o r r o s i o n . I n " C o r r o s i o n Handbook" ed. by H.H. U h l i g . John Wiley and.Sons, Inc., New York (1948). 20. G.I. T a y l o r and H. Quinney. L a t e n t energy remain-i n g i n metal a f t e r c o l d working. . Proc. Roy. S o c , 143,307 (1934). R.W. Prance. L a t e n t energy i n c o l d worked i r o n and copper as estimated by de t e r m i n a t i o n o f the heat o f s o l u t i o n . Trans. Farad. S o c , 30,450 (1934). APPENDIX TABLE I (F»fr. 3,4,5) 2.1 S.W.G-. cold drawn copper wire. Test 6. Soln-lVZ5'o COSOA. Initial load. ZZ9 gms on each u>ir<? T i m e mins <v-s«cs 30 - * s I 2 0O I S 3 0 4* 13=00 /s J40o 15 30 •/*" , 30 f6:0O l i " 30 / 7 00 30 4* 18 00 IS 30 AS 30 Deflection Cms 16 3 7.0 o Zl f 21 6 Z I -4 166 l©0 193 IBS' •2.0 S 10 + 1 9 4 / 9-6 Z5 O 2 S O If Z a/ 6 Zl 6 2 0 4 ao-5 » - - 5 a.'- / 2 Z 8 I90 / 9 7 23 O removed 4 omne^uiirt Z. r<mofct( i r e i*ioe«ot 0-5" on *»ej. r e m o v e / nej.iu/V* 215WG. ceW drawn Copper v»'r«T««t 11. So)>o4-% /VgC/ I n i t i a l loac( ?^9<j»n r\d<Lkopo<i.wf* Time Q e/lecii on ^t^hk ojided mins+*>ecs \ cms | K g s So 4-S-/ - oo / r j« , * r / r 70 ? r j 00 / r zo *<? is-«r Soo / r 3«» If 30 *r 7:00 t-.OO /sr Jo 21 S. IA/ 6 do Id drawn fioppcr \oire T«s^  10 Aearvated. covered Sfamokit Initial load H19<\im Add to po$. vise. Oz flection WjLiQy<idde<( cms K<\% TABLE U. (FI*6) ZIS.W. G. annealed Copper wire Tes t 3. Soln %sCuSQi.-f(i\tA8-SS. Initi'o.1 load too g m s Ti we 2\SWG<&*e&.le.dcopperu>ire Test 5. 2 Jo. T*'ifik/ la+d /it ems Til*** Poieniia.1 AiHcrtt mis <t-.OOo.fn 21S W6 a»*ea/e/copprr u ire Test '4. Sol* "/ztbGiSQf. -filledInitial load itftp* -0-6Z. -o J& -o-36 -0 07 / zr 2 96 7 /* 21 S.W.Gr a.**ea.lfo{Copper u//rv Test 6. Soln %se> Cu-SQ,Mkd Tlo.T»iho.l\o*d /Moms Time. **y m" O 1 Z. J s 6 0 S8 0-38 0-43 -otr -o /f -r*7 -1 c? Q 0 Z oir o-73 6zr IOZ7 //•*+ g 00 r -io. 96 /9.3I8 \/9.3/9 o/r av /f 1 o.iz 2ISWG"dUfieoitdCoppertuinr Test 18 Soln "fx Cu SO4 T M W it* fillmq. Initio.} loaud. il9 q»* /uire TABLE I T (FIGS) /*f S W G Annealed coppf-wi™ Test 2 Sol* 'yjr&.Sfy . Ww( -J /M/y TnifieJ loa.d tooo gm or\tack u>irc 2/6-5 1.63 < ;.2J v ' * r tie I 06 0.93 Tim t *ki$ht*ddtd min m if O o « ©. <r -<>.z* - o . ^ r -•. 12 -©.74 \? 0-4O ft -o. 181. -o.zo -«. a/ -ft 36 -a. 37 rJlS I ("I' - O O I - O . o 2 - c o 1 o o * o. « a o. *> 2.86 2.64-2. 27 2 20 h i m o o o.of ©.** off Z.Br r.if tl8 lot _^ ffl o o.r* o. (6 oio a«t_ ftoo 2 6.7+2 7.16 IIS 0 66 Of« 6.41 0.36 O.t* 0.07 -o.io TABLE SZ (F\&\\) Z4SWG-ojwea\e<( cofptrwi>« Test 16 a.nr>e.oJtcL Copper wire Tzit24-Sclh NaCl. Tested 6 hrs after /,ill mg SJtn IH Tttttd l i hrtfier tiUmtj Ini t ia l load 100 gm on «acJi u<>* TViiH*! \o\ol leoa.** on eacA uJirs Titne Vtiohf Mtstiai £AZ Uncjfkaf JK»WA># 7lwi4 >AAPI«A^ fVUrft*) 24 £ Added dlfftrrtkX Sittiort ^  tddtrf JMftTlKi ristato* in in Kq tviz mis mmsvrti % )>*iin ICQ inr M / meg^ m* /o -3.17 -2+7 -a.cz 83X O 070 o r r I4.TZO 14 667 l+.i3X 24" S W <7AMnt4.(<cf topf>W u)if* Te%t Z& So 1)0 " / i f GxS0* .Tested a***r- 4br. JVlifiaf /(W Xloogman'fastUtre.lagjnrat, after Time I yt'iakfoMdtd \Pot*»ti*ldifortiaA SAC nnitn teo r** mr 16.017 16.US O 036 O.Z2 O.i 7 O. 17 I- 7 t - t'JL -1.79 ~xsy U.eo9\ //•27 , 'I.J? 16.799 16.27 Z4Sv/<ra*. (u utire T«-st 2.S Ttfttd thr tftcr&Hinq mi ft added d;*i*rinc* Kg 11 -3.2 1 -3. 36 -3. S.3 "J 'I 36.06 32. 66 Z7. 99 Hi «* f 7. 6B 2. 1 + 7663 7ie>6 66 o7 Vf *7 71. tl 71. Z» Z + V f r am. cu u»ir« Test U Im'tYa/ load too <}m P.t«.Mfi*l di-H*r*.»CM. -o z3 -OZT 68.69 loasr 9 7.76 92.63 et.ro 9X.S9 re.zs • 3l.oo 0 l.ZO 0 . S 7 o.fo 66.57 7 9. 71 73. II 66.91 I0X.60 17.19. hf.93 82 7/ %md wire zf-trssed s/*nforty-neq &A«.i4«*s -pot-, di-ff- feto xnr l hr- mor€ . 24 SW6- on Cu. u«V-« T««t 29 Tesfad 2 7x hr after -filling -a. 66 -oi9T in 1.3? 1.76 a.ix II. *1 jr.oo /+.+7 o OfJ l.o6 or? 2.83 3. of It* 13. 71 14-36 16-93 /t. rz 16. II lit diff. wax 16 mr -A»r +8*r. ttnd uo'ire str*%std-%iniim.r _ t A I r s _ .. d t a i a e \ . - p » t d i 4 f . -fee* O j + t r a b o u t " t h r t r r o r * . 

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