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

Abstract

Abstract This study investigates the effect of sulfur on Q235 steel and 16Mn steel corrosion in sodium aluminate solution. The corrosion rate of Q235 steel and 16Mn steel reaches the maximum respectively when S2− and S2O3 2− form synergistic corrosion and S2− is contained alone. But, the size of corroded particles is smaller in the solution containing only S2O3 2− for two kinds of steel. The corrosion rate of 16Mn steel is greater than Q235 steel. Surface corrosion of two kinds of steel is both composed of sulfides (FeS and FeS2) and oxides (Fe2O3, Fe3O4, Al2O3 and NaFeO2). The crystal particles of steel surface are mainly iron oxides according to EDS analysis. Nyquist plots of Q235 steel with different forms of sulfur have two capacitance-resistance arcs and no diffusion impedance. Nyquist plots of 16Mn steel with S2O3 2− alone is consistent with Q235 steel. But, Nyquist plots of 16Mn steel presents a typical Warburg diffusion phenomenon with containing S2− alone and forming synergistic corrosion.