Mechanism of grain boundary corrosion of aluminium in high temperature water

Abstract

Mechanism of grain boundary corrosion of aluminium in high temperature water is studied by metallographic and electrochemical methods. It was found that grain boundary corrosion of aluminium in high temperature water showing different behavior from so-called "grain boundary corrosion" was governed by (1) grain boundary diffusion of hydrogen atoms, (2) over-voltage of hydrogen produced by the reaction between aluminium and water and (3) the property of surface film on aluminium. In demineralized water, the rate of corrosion of pure aluminium is determined by the grain boundary diffusion of hydrogen atoms and by the effect of small amounts of cathodic elements on the surface film properties. In dilute acidic solution, grain boundary corrosion of pure aluminium does not occur and this is explained by the low over-voltage of hydrogen in the solution.