Corrosion behavior of a high-strength steel E690 in aqueous electrolytes with different chloride concentrations

In this paper, the corrosion behavior of E690 steel with different chloride concentrations was studied. Combined with the corrosion weight loss, corrosion morphology, corrosion products, electrochemical phenomenon, and the transformation process of corrosion products, the influence of different Cl− concentrations on the corrosion characteristics of E690 steel was studied. The results showed that the corrosion rate of E690 steel increased with the increase of Cl− concentration, and the corrosion rate reached the highest at 3.5% Cl− concentration, and then decreased. The corrosion morphology and electrochemical properties of E690 steel were consistent with the corrosion rate. At the initial stage of corrosion, The concentration of Cl− affected the corrosion resistance of E690 steel by affecting the reaction process of anode and cathode. When Cl− is less than 3.5%, Cl− had an anodic depolarization effect on E690 steel and accelerated anodic dissolution. When Cl− reaches 3.5%, the diffusion of oxygen was hindered, and the existence of film of Fe(OH)2 also reduced the dissolved oxygen in the film environment on the metal surface, leading to the weakening of corrosion. In addition, Cl− affects the corrosion resistance of E690 steel by affecting the transformation of corrosion products. When Cl− in solution reaches 3.5%, β-FeOOH appears in corrosion products of E690 steel. Compared with γ-FeOOH, β-FeOOH is highly reductive and can be rapidly reduced to Fe3O4, thus accelerating the corrosion reaction.