Tribo electrochemical behavior of ferrite and ferrite-martensite stainless steels in chloride and sulfate media

摘要

Tribo-electrochemical behaviors of commercial grade of ferrite and ferrite-martensite stainless steels are compared in solutions containing chloride and sulfate anions. Wear is performed by reciprocating sliding motion with an inert counter body. Surfaces are electrochemically characterized before and after wear and a data treatment of potential evolutions during sliding is proposed in order to distinguish the ability of passivation/depassivation of materials. If the coefficient of friction is independent of the microstructure, the calculated wear factor increase for the dual phase steel due to a mechanical interaction between the brittle and soft phases and the aggressiveness of chloride which promote localized corrosion at the interfaces. However, the dual phase keep a better pitting resistance compare to ferrite steels mainly due to a slightly higher chromium and nickel content. When friction experiment occurs, evolutions of potentials are recorded and treated according an exponential law during the idle period (as observed for the load of capacitor) and an linear law when friction occur. Results show that the depassivation rate is only controlled by the solution chemistry whereas the kinetic of repassivation is depending of the chromium and nickel content on material and with a lower impact of the solution composition.