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

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 S ^2− and S _2 O _3 ^2− form synergistic corrosion and S ^2− is contained alone. But, the size of corroded particles is smaller in the solution containing only S _2 O _3 ^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 FeS _2 ) and oxides (Fe _2 O _3 , Fe _3 O _4 , Al _2 O _3 and NaFeO _2 ). 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 S _2 O _3 ^2− alone is consistent with Q235 steel. But, Nyquist plots of 16Mn steel presents a typical Warburg diffusion phenomenon with containing S ^2− alone and forming synergistic corrosion.

Keywords

• Q235 steel
• 16Mn steel
• sulfide
• thiosulfate
• corrosion