STOCHASTIC APPROACH TO THE EFFECT OF ALLOYING ELEMENTS ON THE PITTING RESISTANCE OF FERRITIC STAINLESS STEELS.

Abstract

Birth and death stochastic processes are confirmed in pitting corrosion of ferritic stainless steels containing Cr, Mo, Ti and Nb. Birth process corresponds to pit generation and death process to pit repassivation, each rate being determined as a function of potential by the analysis of survival probability vs. time curves. Pitting potential shifts to the noble value with the addition of all the alloying elements. The shift by alloying Cr, Ti and Nb is caused by a decrease in pit generation rate, while pit repassivation rate remains constant. The addition of Mo enhances the rate of repassivation and decreases the pit generation rate.