The Chemical Nature of Aluminum Corrosion: V . Energy Transfer in Aluminum Dissolution

The transfer of energy during the dissolution of aluminum is represented by a potential energy surface. In chloride solution, the high energy aluminum metal ionizes rapidly to the Al +++ ion which also hydrolyzes rapidly. At the start of the reaction, in the microsecond range, there are two species available for reaction, Al +++ and . The reaction follows two alternative paths; the energy levels of the alternative species, and have been measured. These two species react further to form a reasonable stable basic aluminum chloride that is transformed slowly to and finally to . The energy levels of these species have been measured. Reaction in sulfate solution differs because the intermediate species, and occupy low energy levels, and the basic aluminum sulfate has a lower energy than . In most practical cases of aluminum corrosion, the reaction proceeds in the reverse direction. The reactants are the oxide‐covered aluminum surface and the anion combining to form the basic aluminum salt.