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.

When alumina is produced by the Bayer process with high-sulfur bauxite, the sulfur would strongly corrode the 12Cr1MoV steel made heat exchanger. This study investigated the initial corrosion behavior of the 12Cr1MoV steel exposed to a thiosulfate-containing sodium aluminate (TCSA) solution under the evaporation conditions of alumina production. The obtained corrosion rate equation is V = 6.306·t·exp(−0.71). As corrosion progressed, with the corrosion product film growing, the corrosion current density declines slowly, and the corrosion resistance of the steel is increased. At 1–3 days, the corrosion product film consisted of FeO, Fe2O3, and FeOOH. S2O32− lead to corrosion in local areas of the steel and pits appeared. AlO2− is transformed into Al(OH)3 and filled in the corrosion pits. At 4 and 5 days, Fe3O4 is generated in the outermost layer, and Al(OH)3 is shed from the corrosion pits. The corrosion mechanism of 12Cr1MoV steel in a TCSA solution is proposed based on the experimental results.

This study investigates the effect of corrosion temperature on the corrosion of Q235 steel and 16Mn steel in the sodium aluminate solution using the weight loss method and electrochemical method. The results indicate that the corrosion rates of two steels show an increasing trend with the temperature and that of Q235 steel increases more than that of 16Mn steel at higher temperatures. The corrosion products have changed from four forms at 25 °C to two forms at 65 and 110 °C, namely, the octahedral particles and the bulk particles formed by the flocculent aggregation. The corrosion products are composed of FeS, FeS 2 , Fe 2 O 3 , Fe 3 O 4 , NaFeO 2 , and Al 2 O 3 . The I corr of the two steels increases with temperature, while R p gradually decreases. The two steels are controlled by the charge transfer at 25 and 65 °C and the charge transfer and the ion diffusion at 95 °C, indicating that the temperature changes the kinetics of the corrosion process.