Electrochemical modeling of passivation phenomena in tribocorrosion

The relationship between repassivation behavior and tribocorrosion is investigated using an iron–chromium alloy (AISI 430) in sulfuric acid as a model system. Tribocorrosion experiments were performed in a reciprocating motion apparatus under electrochemical polarization. A constant potential in the passive region was applied and the current variation during individual stroke periods was measured as a function of applied potential and stroke frequency. Theoretical models were developed taking into account the film growth kinetics and the ohmic drops in the electrolyte between wear scar and reference electrode. The model could simulate the general trends observed in the current transients but the agreement with experimental data was only fair. Several reasons for this are discussed. They include pin surface roughness influencing the real depassivated area, insufficiently known electrochemical conditions in the contact zone and role of third body particles.