On the problem of setting a criterion for pitting resistance of stainless steels

A comparative analysis of the currently existing criteria for the pitting resistance of stainless steels and the proposed criterion based on the formation potential of a salt film is carried out. The formation potential of the salt film is shown to provide an explanation of the current oscillations, which are a typical feature of pitting corrosion, as well as to fairly accurately predict the pitting-resistance ranges of stainless steels. The combination of the existing and proposed criteria for pitting resistance enabled us to more accurately distinguish the three possible states of a passive film, namely, the range of a passive state or stable passivity where the probability of the formation and development of the earlier appeared pits equals zero, the range of a meta-stable state or instable passivity where the existence probability of the earlier formed pits and the nucleation probability of repassivating pits are nonzero, and the range of pit formation where the formation and stable growth of pits are possible.