Crevice Corrosion of Stainless Steels

―Initiation＆Propagation Mechanism and Its Evaluation Tests―

Abstract

This paper is the comprehensive paper on the crevice corrosion mechanism for stainless steels by using the newest in-situ instruments. The in-situ observation apparatus, the in-situ semiconductor pH sensor and the in-situ raman spectroscopy were applied to the study of the crevice corrosion behavior of stainless steels in Cl^－ solution. The propagation of crevice corrosion was divided to 4 stages of Stage I～Stage IV. The propagation behavior in these Stages was closely related to the hydration and the formation of metal coordination compounds （hydrolysis and chlorido complex ions）. The reppassivation of crevice corrosion was achieved by the pH raise resulting from hydrogen generation in the crevice as cathodic reaction. Furthermore, it was cleared that the initiation of crevice corrosion was caused by the metastable pitting in the crevice.

The new evalutation methods on the initiation and propagation of crevice corrosion were proposed.