Localized corrosion and stress corrosion cracking of stainless steels in halides other than chlorides solutions: a review

Abstract

Fluorides, bromides, and iodides, despite being less common than chlorides, are present in various environments of industrial relevance. Stainless steels suffer pitting corrosion in solutions of all halides except fluorides, which can be understood considering that fluoride is the anion of a weak acid. The aggressiveness of the rest of the halides for pitting corrosion is on the order Cl- > Br- > I- for stainless steels with Mo content below 3 wt.%. Mo is not as effective in inhibiting Br- pitting corrosion as it is for inhibiting Cl- pitting corrosion. Most of those observations were rationalized based on the effect of anions on pit growth kinetics. Sensitized austenitic stainless steel suffers stress corrosion cracking (SCC) in solutions of all halides, albeit chlorides seem to be the most aggressive. Fluoride SCC is relevant for SCC under insulation of stainless steels, and standards and regulations developed to mitigate this problem consider this ion as aggressive as chloride. For the solubilized stainless steels, aggressiveness toward SCC is in the order Cl- > Br-. The SCC of solubilized stainless steels was not observed in solutions of F- and I-, and the possible reasons for this fact are discussed.