Abstract

Corrosion behavior of Hastelloy C-22, Ti-0.2Pd and Ti-32Mo alloys in the aqueous solution of hydrochloric acid and sodium chlorate was investigated. The C-22 alloy was pitted because the intergranular carbides rich in Cr and Mo would lead to the lack of corrosion-resistant elements in the adjacent area. The Ti-0.2Pd alloy was pitted because the passivation trend decreased in reducing solution and Cl− broke through the passivation film. The weigh loss rate and corrosion depth of Ti-0.2Pd alloy increased sharply after pitting corrosion, which was due to the rapid corrosion of the materials exposed inside by the corrosion medium. The Ti-32Mo alloy was pitted due to the transpassivation of Mo caused by NaClO3. In the process of corrosion, the products of reaction between Mo and Cl− formed an insoluble and dense protective film, which slowed down the corrosion rate of Ti-32Mo, that is why the weigh loss rate and corrosion depth increased slowly even if pitting corrosion happened.

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