Intergranular Dissolution of Zinc Alloy Sacrificial Anodes in Sea Water at Elevated Temperature

Abstract

Severe intergranular dissolution of a zinc alloy sacrificial anode operating at above ambient temperature under heat transfer conditions in sea water has been reported. This type of failure has been simulated in isothermal electrochemical studies in artificial sea water at 70°c, using both galvanostatic polarisation and galvanic coupling techniques. Electron probe microanalysis and Auger Electron Spectroscopy suggest that the localised dissolution is linked with the migration at 70°c of aluminium to the grain boundaries, and the subsequent preferential removal of the aluminium-rich phase thus formed. A means of overcoming the problem is suggested.