Synergistic effect of the total acid number, S, Cl, and H₂O on the corrosion of AISI 1020 in acidic environments

The corrosive environment in sulfur-containing equipment is often complicated and changeable. This study adopted the Taguchi method to optimize the immersion test, and the L27(313) orthogonal table was used to design an immersion corrosion experiment. The influence of four factors, namely, the total acid number (TAN), sulfur, chlorine, and water, on the corrosion of AISI 1020 in the oil phase was studied. It showed that the effect of chlorine is the most pronounced and that of sulfur is second followed by that of the TAN and H2O. It was also found that the effect of H2O exceeds that of the TAN after 336 h; meanwhile, the interaction between the four factors varies over time and stabilizes after 336 h. Moreover, corrosion rate curves reveal that the stable corrosion product film formed on the metal surface gradually slows down the corrosion process. Analysis of corrosion morphology and product composition was done by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Overall, the synergistic effect of the corrosion rate changing with time provides a certain reference for the corrosion protection of sulfur-containing storage equipment.