Resistance of Aluminum to Corrosion in Solutions Containing Various Anions and Cations^*

The rate of corrosion of aluminum is controlled by the protective oxide film which forms when an aluminum surface is exposed to the atmosphere. This film, although very thin and usually invisible to the unaided eye, is highly protective and resists attack under many conditions of service. It is to this inert film that aluminum owes its inherent high resistance to corrosion. The corrosion mechanism for aluminum in neutral or nearly neutral solutions is usually accompanied by the formation of additional hydrated aluminum oxide which deposits on the surface of the metal and tends to serve as a barrier to further attack. For this reason the attack by some solutions may be relatively rapid at first, but as the insoluble products of the reaction are formed, an adherent, continuous film covers the metal which further reduces the probability of contact of the solution with the underlying metal and as a...