Effect of the applied potential of the near surface microstructure of a 316L steel submitted to tribocorrosion in sulfuric acid

The tribocorrosion behaviour of a 316L austenitic stainless steel sliding against alumina was investigated under electrochemical control in sulfuric acid using a tribometer with a ball on flat configuration. Tests were conducted by applying either a passive potential (metal covered by an oxide film) or a cathodic potential (no passive film, negligible corrosion) to the steel. Friction, wear and anodic current were monitored. The near surface microstructure of wear tracks was analysed by transmission electron microscopy (TEM). Significantly higher wear was observed at the passive potential compared with the cathodic potential. Chemical reactions could not account for this difference in deterioration. TEM analysis revealed that the plastic behaviour of the metal, and thus its response to wear, depends on the prevailing electrochemical conditions, the passive potential showing larger deformation than the cathodic. This effect was attributed to the presence of the passive film that induces residual stresses and interferes with dislocation activity.