Effect of the elastic tensile load on the electrochemical corrosion behavior and diffusible hydrogen content of ferritic steel in acidic environment

Linear polarization resistance (LPR) and potentiostatic polarization measurement are employed to determine the influence of tensile stress in the elastic range on the electrochemical corrosion and hydrogen reduction behavior of ferritic steel in a sour environment. For a more mechanistic study, the experimental polarization data were fitted using the Wagner-Traud equation, and the reaction parameters related to the sour corrosion of ferritic steel under an applied load condition were obtained. This study revealed that elastic loading condition led to higher anodic and cathodic reactions of the steel, resulting in a significant increase in corrosion current and a decrease in polarization resistance. In particular, the hydrogen evolution rate induced by the cathodic reduction reaction increased significantly under an applied elastic load. The generation of molecular hydrogen in the pre-formed sulfide film can contribute to weakening the stability of the sulfide film by suppressing normal growth of the film. Consequently, the diffusible hydrogen contents in the steel increases under the stress condition, resulting in a higher susceptibility to hydrogen assisted cracking failure. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.