Aluminium corrosion studies. II. Corrosion rates in water

Abstract

The corrosion rate of aluminium in flowing neutral waters at 50°C has been determined as a function of pH, oxygen concentration and chloride concentration. The corrosion rate, A_t, as total aluminium lost between the 4th and 80th day was observed to be logarithmic according to A_t = B log t+C with a minimum rate in the pH range 5-6, and with B c. 3 x 10^-5g cm², C c. 20 x 10^-5 g cm^-2 and t in days for oxygen-saturated water. Saturating the water with nitrogen or adding up to 15 mg Cl^- l^-1 increased the corrosion rate. It was concluded that this was due to competitive action on the oxide surface, between dissolved oxygen and chloride ions.