Chemistry of Crevice Corrosion as Observed in Certain Cu-Ni and Fe-Cr Alloys

In occluded cells, such as crevices, the chemical composition of the electrolyte tends to change dramatically with time from the original bulk composition. The consequences of such changes are reviewed using the binary Cu-Ni and binary Fe-Cr systems as examples. In the case of the copper base alloys, conditions leading to certain dealloying reactions are reported. The concept of a crevice protection potential is confirmed for chromium modified 70–30 Cu-Ni. The possible influence of the presence of complex ionic species in determining the extent of acidification within crevices in Fe-Cr alloys in saline solutions is reported using thermodynamic models in combinations with experimental observations.