Corrosion and fouling study of copper-based antifouling coatings on 5083 aluminum alloy

Abstract

Potentiostatic and electrochemical impedance spectroscopy (EIS) were used to evaluate cuprous oxide (Cu2O) containing coating systems on the localized corrosion of 5083 marine-grade aluminum in simulated ocean water. Test panels coated with a complete coating system and flawed to simulate a coating defect were also exposed for a 3-month field immersion to evaluate differences between Cu2O and cuprous thiocyanate (CuSCN) pigments on fouling and corrosion behaviour. Optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to evaluate deposits formed on the surfaces after exposure. Results imply that copper leaching from the Cu2O pigment can deposit on the surface marine-grade aluminum, with or without cathodic protection. Cathodic protection resulted in the formation of protective calcareous deposits at potentials more electronegative than −1000 mV versus silver-silver chloride (Ag/AgCl). Cuprous oxide was shown to be a more resistant to biofouling than the cuprous thiocyanate, but there was an increased likelihood of coating delamination and localized corrosion with the former antifouling pigment.