Abstract
Repeated measurement of pitting potentials has been accomplished for 304 and 316 stainless steels in 3.5% NaCl solution deaerated with nitrogen gas at 35°C, using a potentio-kinetic method (20mV/min). Chemical etching using 30% H2SO4 for 10min at 35°C or mechanical polishing with 2/0 emery paper is used for surface preparation. It is clarified that measured values are described as a normal distribution, which is easily demonstrated by plotting measured values arranged in ascending order and corresponding probability in a normal probability paper. Although a well controlled condition is used, fairly large standard deviation, or coefficient of variation, is found, the order of which is comparable to that of fracture strength of solid material. Application of “the weakest link model” which is originally developed in fracture phenomena to pitting corrosion is suggested.
