Effects of S2- and S2O2- 3 -Containing Bayer Solutions on Corrosion of 16Mn Low-Alloy Steel at Elevated Temperatures

Serious pipe corrosion caused by accumulated S2- in Bayer solutions occurs when treating high-sulfur diasporic bauxite by the Bayer process at elevated temperatures. The effects of S2- and S2O23- anions on the corrosion behavior of 16Mn low-alloy steel have been investigated under simulated high-temperature Bayer digestion conditions. The structure of the corrosion layers was analyzed. Results show that S2- anions markedly accelerate such corrosion because of the generation of loose FeS-containing corrosion product, whereas S2O3~ anions with concentration > 8.7 g L-1 can remarkably retard the corrosion process by forming a compact magnetite layer with dense and fine particles. Corrosion surface topography analyses support all the experimental corrosion results. Thus, S2O23- represents an effective corrosion inhibitor for 16Mn low-alloy steel, and S2- to S2O23- transformations may contribute to preventing equipment corrosion when using high-sulfur bauxite in the Bayer process.