Corrosion of Cu and Cu-Ni Alloys in 0.5M NaCl and in Synthetic Seawater Available to Purchase

Electrochemical corrosion rates of Cu and Cu-Ni alloys have been measured in oxygenated 0.5M NaCl and in synthetic seawater using the Tafel extrapolation procedure. In addition, Cu corrosion has been measured with the linear polarization procedure. A rotating disk electrode system was used in the measurements with rotation rate varying from 500 to 6000 rpm. The corrosion characteristics of Cu and 90Cu-10Ni alloy in the two media, and 70Cu-30Ni alloy in 0.5M NaCl have been found to be similar. For these systems, the variation of corrosion current, corrosion potential, and anodic partial current with rotation rate of the electrode could be explained in terms of a convective diffusion controlled corrosion mechanism incorporating the generation of a soluble copper complex on the electrode surface. The 70-30 alloy in synthetic seawater behaved differently. Corrosion current, corrosion potential, and the anodic partial current were all constant with rotation rate, indicating a surface kinetic-controlled corrosion mechanism.