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Corrosion protection performance of cathodically protected oil and gas pipeline coatings around the transition temperature

University of British Columbia

Oil and gas pipelines are susceptible to corrosion by reacting with their environments. Water, oxidants, acids, and alkalis can act aggressively on the steel substrate. Over the years, corrosion has been the cause of many catastrophes. Thus, to prevent or slow down corrosion from taking place on steel substrate two techniques are primarily used. These techniques are coatings and cathodic protection. While the principles of cathodic protection is basically to reduce corrosion potential, coatings protect metals by breaking corrosion cells and provide shielding from corrosive agents. However, coatings should exhibit certain characteristics in order to be considered effective it terms of corrosion protection. Coatings have to withstand severe weather including temperature changes. Pipelines often operate at high temperatures due to the heat generated from crude frictions during transfer. With higher demands for crude oil and products, pipelines might be operated at flow rates more than normal and temperatures may exceed transition temperature (Tg) of the coatings. All thermoplastic materials have an important material property resulting from the molecular movement of the side chains of the polymer, Tg. It affects many polymer properties. In literature, it is not quite clear whether Tg affects corrosion protection properties or not. In this work, behavior of two polymer coatings, namely SP8888 and SP2888 provided by Specialty Polymer Coatings Inc., have been studied at temperatures around their Tg using Electrochemical Impedance Microscopy (EIS) in combination with Electrochemical Noise (EN). From the experimental work results, it was found that coating capacitance (Cc) has slightly increased and coating resistance (Rc) has decreased as temperature was increased over the range of test. There was a slope change for both Rc and Cc around Tg. Charge transfer resistance (Rct) has shown an abrupt drop as the temperature approached Tg. Generally, the estimated Tg value from Z modulus was in good compatibility with the Tg measured with other DSC technique.

Text

2014-05-27

Attribution 2.5 Canada

http://hdl.handle.net/2429/46840

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by/2.5/ca/