Pc. Pistorius et Gt. Burstein, ASPECTS OF THE EFFECTS OF ELECTROLYTE-COMPOSITION ON THE OCCURRENCE OF METASTABLE PITTING ON STAINLESS-STEEL, Corrosion science, 36(3), 1994, pp. 525-538
The rate of formation of metastable pits on type 304 stainless steel s
urfaces in chloride solution is examined as a function of the chloride
concentration and pH. The frequency of pitting events decreases as th
e chloride concentration is reduced; the effect arises from a concomit
ant reduction in the number of available sites at which metastable pit
ting can take place. The electrolyte pH has no observable effect on th
e frequency of metastable pitting, and no effect on the number of avai
lable sites. The results are consistent with the hypothesis that the a
bility of a metastable pit to develop at a particular site depends on
the geometry of the site. Preliminary experiments on the effects of ae
ration show that dissolved air reduces the frequency of occurrence of
metastable pitting current transients. The effect of oxygen remains un
explained.