The nature of the metal/film interface and the nature of the surface film formed on a 90/10 Cu-Ni alloy during stress corrosion cracking (SCC) in a 1 M sulfide solution were investigated with the help of x-ray imaging and electron microprobe techniques. The surface film consists of an inner oxide-rich layer (4 to 5 μm thick), deficient in Cu and S but rich in Ni and Fe, and an outer sulfide layer (~20 μm thick), rich in Cu but deficient in Ni, Fe, and O.
The metal/film interface is depleted in Cu as compared to the bulk alloy composition over a distance of 1 to 1.5 μm with a corresponding Ni enrichment in the same area, indicating that Cu undergoes preferential dissolution from the 90/10 Cu-Ni matrix when exposed to 1 M sulfide solution.
National Association of Corrosion Engineers
1991
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