Corrosion-wear of passivating materials in sliding contacts based on a concept of active wear track area

The concept of active wear track area is proposed as a way to investigate the mechanism of the corrosion-wear behavior of passive materials under sliding conditions. This active wear track area represents that part of the wear track that looses temporarily its passive character due to the mechanical interaction during sliding. It is shown that the active wear track area can be determined from repassivation kinetics measured on electrochemically activated material by a potential pulse method, and from anodic currents measured during sliding ball-on-disk tests. The use of that concept is illustrated for the case of stainless steel AISI 316 immersed in a 0.5 M H2SO4 solution. At loads below 2 N, no breakthrough of the oxide film is noticed. At loads between 2 and 12 N, the corrosion-wear agrees well with Quinn’s mild oxidation wear mechanism. The corrosion-wear of AISI 316 consists then of two processes namely a mechanical delamination of the passive layer in part of the wear track, followed by a progressive electrochemical re-passivation of that active wear track area. The thickness of the passive layer on AISI 316 was derived from the active wear track area and the electrochemical response of passive and active AISI 316 material. A value of 2–3 nm was obtained that agrees well with data obtained by other methods. Above a load of 12 N, the corrosion-wear increases steeply due to a degradation process involving abrasion and/or breakdown of more than just the oxide film.