Corrosion behaviour of aluminum-base alloys in desalination plants

To reduce the susceptibility of aluminium tubes to pitting corrosion when in contact with seawater at elevated temperatures, the effects of a number of alloying elements (magnesium, chromium, manganese, zinc, and tin) on resistance to this form of corrosion in aluminium-base alloys were investigated. Tests were carried out in simulated Caspian sea water at 70C and electrochemical measurements were made with the aid of a rotating disc electrode in solutions agitated at 50C. Changes in the nature and extent of surface films during exposure were also studied. The incorporation of manganese at up to 1 per cent by weight reduced the tendency to pitting corrosion, while aluminium-magnesium alloys with chromium as an additional element also possessed superior resistance to both pitting and generalized corrosion damage on exposure to sea water.