Effect of sulfur on synergistic corrosion behavior of Q235 and 16Mn steel in sodium aluminate solution

In this study, the corrosion electrochemistry and corrosion behavior of two steels were studied under the simulated alumina production conditions. The corrosion rate of 16Mn steel is greater than that of Q235 steel. The effect of S^2- concentration on corrosion rate was significantly higher than that of S₂O₃^2-. The synergistic corrosion rates of Q235 and 16Mn steels increase at first and then decrease with the sulfur content, and the peak value appears when the concentration of S^2- and S₂O₃^2- is 4 g/L and 3 g/L respectively. There are two main types of corrosion products: one is surface octahedral grain, which is composed of Fe₂O₃, Fe₃O₄ and Al₂O₃.The other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS₂ and NaFeO₂.The formation mechanism of the corrosion and corrosion mechanism were obtained by analyzing the phenomenon of ion competitive adsorption. Further validation and analysis of ion competition adsorption phenomenon were conducted using first-principles calculations based on density functional theory (DFT). The formation of corrosion products on the steel surface was investigated at an ion level, and the adsorption energies of OH^- and S^2- at the top site of Fe(110) surface were calculated. It was found that S^2- is more likely to be adsorbed on the Fe(110) surface compared to OH^-. The corrosion mechanism of steel is discussed preliminarily.