Effect of Sulfide-Containing Solutions on the Corrosion of Cu-Ni Alloys; Electrochemical and Surface Studies

Abstract

The effect of sulfide ions on electrochemically grown films over 90Cu-10Ni alloy in sulfuric acid, sodium sulfate and chloride-containing electrolytes at different polarization time intervals is investigated. The highest corrosion rates are in solutions of sulfate containing chloride in presence of 20 ppm sulfide. The lowest rate for copper dissolution is in sulfuric acid containing chloride in presence of sulfide. The rate of corrosion increases with increasing temperature and the activation energy was highest in sodium sulfate. Nickel dissolution is highest in presence of sulfide. XPS measurements revealed that Cu2S was formed and resulted in further dissolution of the films protecting the alloy. Noticeable decrease in polarization resistance of the alloy is observed as the film dissolution increases and metallic concentration in the electrolytic side increases. EIS results showed that in presence of sulfide the oxide film resistance in sulfate-containing electrolytes is higher than in chloride.