Investigation of corrosion behavior and film formation on 90Cu-10Ni alloys immersed in simulated seawater

The corrosion behavior and formation of the corrosion product film of three 90Cu-10Ni alloys, namely Pipe A, Pipe B, and Pipe C, after being immersed in simulated seawater for different time were investigated using electrochemical techniques, electron backscattered diffraction (EBSD) technology, scanning electron microscopy/energy-dispersive X-ray detector (SEM/EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that there were no obvious differences in chemical composition, but some differences in grain size and number of annealing twins for the three alloys. Pipes with large grains and fewer annealing twins had better corrosion resistance. It was found that a protective corrosion product film enriched with Fe and Ni was formed on the surface of the alloys after different immersion periods. The corrosion current densities Icorr of the alloys decreased while the film resistance Rf increased with time. After 30 days of immersion, a hollow and discontinuous layer was identified on Pipe C. Compared to Pipe C, the other two pipes showed better corrosion resistance, which was due to a compact and continuous layer bonding firmly with the substrate. The formation process of the corrosion product film on 90Cu-10Ni alloys with the increasing immersion time in simulated seawater was discussed.