The enrichment of hydrogen and chloride ions in the crevice corrosion of steels

The changes in concentration of hydrogen and chloride ions during corrosion in an artificial crevice on steel were observed from potential changes of Pd-H and Ag/AgCl micro-electrodes inserted in the crevice. Increasing the bulk chloride ion concentration accelerated the rate of pH change and resulted in more acidic conditions in the crevice. Such pH changes were delayed by the addition of inhibitor such as dialkylamines. Though the free chloride ion concentration did not change appreciably, the total concentration of free and complex ions in the crevice increased with continuous dissolution of the steel. Increasing the hydrogen and total chloride ion concentration in the crevice accelerated the anodic dissolution of steels within the crevice.