Aluminium corrosion studies. I. Potential-pH-temperature diagrams for aluminium

Abstract

The potential-pH-temperature relationships for the aluminium-water system have been calculated by the methods of de Bethune, Khodakovskiy, Criss and Cobble, and Helgeson and a critical comparison made. The Criss and Cobble method produced the most consistent results and was used to construct a corrosion diagram for the range 25-300ºC. The effect of the hydrolysed ions Al(OH)²⁺, Al(OH)₂⁺ and Al(OH)₃⁰ was also calculated. The work has shown up a temperature effect which should be taken into account when designing and operating aluminium circuits in which different parts are operated at different temperatures.