Stress Corrosion Cracking of Copper-Nickel Alloys: A Review

Under the combination of certain corrosive ions and stress, Cu-Ni alloys may experience severe stress corrosion cracking (SCC), which causes premature failure and hinders their further applications as crucial construction materials in various engineering fields. To reveal the origin of such failure, minimize the related negative impacts, and achieve economic and social benefits, this review summarizes all SCC-related issues by making a brief introduction to Cu-Ni alloys, reporting the SCC behavior in various environments, identifying the effects of different factors during SCC, and revealing the SCC degradation mechanisms. S2- and NH4+ are the prominent SCC initiators since the former can combine with Cu+ to form Cu2S as a non-protective corrosion product, while the latter has a great tendency to react with Cu2O/Cu and accelerate the general or local dissolution. Their combination has the most detrimental effect. The SCC mechanisms of Cu-Ni alloys are summarized as film rupture theory and dealloying theory. The related SCC mitigation strategies, including using inhibitors, tailoring alloying elements, and removing/reducing the stress are also discussed. In addition, future directions are made at the end of this paper.