Tribocorrosion behaviors of 304SS: effect of solution pH

Abstract

The tribocorrosion behavior of 304SS in chloride-containing solutions with different pH (pH 7.2–9.2) was investigated under rubbing conditions of 50 N and 100 R min⁻¹ using a pin-on-disc tribometer with an Al₂O₃ pin mounted on a vertical rotating axis. When combined with rubbing, the corrosion of 304SS was accelerated due to the formation of galvanic couples between the mechanical depassivated areas and the surrounding passivated areas. In addition, the continuous sliding-over processes also make the pitting corrosion to occur more easily due to the affinity of Cl⁻ to metal cations near the active surface. However, OH⁻ has better affinity than Cl⁻; therefore, a high pH solution mitigates the local corrosion with a wear track. It was found that high pH solution exhibits good lubricity, and both the friction coefficient and total material loss reduce evidently with increasing pH. From the calculation results and wear morphologies, we can confirm that pure mechanical and corrosion-accelerated wear, including abrasion and delamination, are among the chief reasons for material loss.