Influence of Alloying Element Contents on Corrosion Properties of AH32 Steel in Wet Atmosphere Containing H₂S

The effects of alloy element contents on corrosion properties of the AH32 steel in the briny wet atmosphere containing H2S simulating the cargo oil tank corrosion environment were investigated by corrosion rate measurement, SEM, EDS and XRD. The results show that the corrosion rate of AH32 steel with higher alloy content was higher in the initial stage , and then decreased rapidly after 21 d due to higher contents of Ni, Cr, Cu, V and Nb. The corrosion resistance of the higher alloying AH32 steel was better than that of the lower alloying AH32 steel. The main corrosive products on the surface of the both AH32 steels with higher and lower alloy content are identified as FeS1-x, FeS, Fe3O4, α-FeOOH, β-FeOOH, and γ-FeOOH. The electrochemical corrosion controlled by the diffusion of H2S and O2 under the liquid film was the main corrosion mechanism. HS- depolarizing process became increasingly dominant with the increase of corrosion time.