Corrosion Behavior of X80 Steel Under Anodic Polarization

To investigate the corrosion behavior of X80 steel caused by an anodic current density, electrochemical tests of X80 steel in near-natural NS4 solution under varying anodic current densities, I-ac, were performed. The testing combined a three-electrode and direct-current source. Analysis included electrochemical testing and corrosion morphology. The results show that the corrosion behavior of X80 steel in NS4 solution is mainly divided into two stages. The first stage, I-ac=0-20 mA/cm(2), was characterized by the formation of a double electric layer and a corrosion-product layer mainly comprised of FeOOH. During this stage uniform corrosion occurs and I-corr increases linearly. In the second stage where I(ac >=)50 mA/cm(2), the corrosion morphology is pitting corrosion and I-corr is basically unchanged. Black Fe3O4 is the primary inner layer corrosion product that inhibits uniform corrosion and promotes pitting corrosion.