The distribution of the breakdown potential of stainless steels: Effects of test repetition, specimen exposure surfaces and threshold current

Abstract

The breakdown potential has been determined for more than 1000 specimens of stainless steels in 0.1 M HCl solutions in cells housing up to 100 specimens together. The results obtained indicate that: (a) the distribution of survival probability may or may not follow a normal Gaussian distribution; (b) on repetition of the test, both normal Gaussian and other distributions may be followed by either normal Gaussian or other distributions; (c) no evidence of correlation has been found in breakdown potentials obtained in successive tests on the same specimens; (d) the probability of localized corrosion initiation is not found to be directly proportional to specimen exposure area — in some cases it appears independent of this; and (e) the choice of the threshold current value at which to consider individual specimens attacked influences survival probability distribution a great deal. The higher the passivation current density of the material in the ambient considered, the higher the survival probability.