Inhibition and Acceleration of Aluminum Corrosion Available to Purchase

The inhibition of the corrosion of aluminum alloy 2024-T3 in sodium chloride solution was investigated from the view of the chemical species (complexes, compounds) possibly formed with aluminum ion. Four classes of compounds were considered: (I) As a basis for comparison, inorganic oxyanions, chromate, nitrate, perchlorate, and sulfate. (II) The sodium salt of citric acid, a monohydroxy tricarboxylic acid and tartaric acid, a dihydroxy dicarboxylic acid. (III) The sodium salts of acetic, benzoic, and oxalic acids. (IV) Compounds that are known to form stable complexes or compounds with aluminum, such as azelaic acid, benzotriazole, cupferron, oxamide, and quinaldic and rubeanic acids. Inhibitor efficiencies were measured for 14 day immersions and compared with linear polarization measurements. In group I, only chromate gave complete protection, the other anions offering, at certain concentrations, both inhibition and accelerated corrosion (synergistic effect). In group II, both citric and tartaric gave accelerated corrosion at certain concentrations. Of the group III, species, sodium benzoate gave good protection, acetate and oxalate only fair (~ 50% efficiency). Of the group IV compounds cupferron, azelaic acid, and benzotriazole offered fair inhibition. These results are interpreted in terms of the species that are formed with the aluminum ion.