Tribocorrosion behaviour of Fe–17Cr stainless steel in acid and alkaline solutions

The effect of applied potential, load and frequency on the tribocorrosion behaviour of a ferritic stainless steel in aqueous solution is investigated under sliding wear conditions using a reciprocating motion tribometer including an alumina pin sliding on a metal plate. The tribometer is equipped with a reference electrode and a counter electrode for electrochemical experiments. The total metal removal rate of the stainless steel is determined from the rate of penetration of the pin and from an analysis of the wear track at the end of a wear experiment while the fraction of electrochemically removed metal is deduced from the current measured during the wear experiments. Two electrolytes are used, 0.5 M H₂SO₄ and 1 M NaOH. Applied potentials are in the passive potential region except for a few experiments performed under cathodic polarisation. The obtained results demonstrate the interdependence of electrochemical and mechanical mechanisms and the importance of the passivation behaviour of the metal in the electrolyte used. In sulphuric acid the electrochemical metal removal rate depends strongly on the value of the applied potential in the passive region, but not in NaOH because in the latter electrolyte the anodic charge serves only for film formation rather than dissolution. The effect of mechanical parameters on the rate of electrochemical metal removal is in qualitative agreement with a previously developed model. The presence of debris in the contact after test was found to depend on the prevailing electrochemical conditions.