Prevention of corrosion in aircraft —an overview of the evolution of materials and protective treatments

CIM Bulletin, Vol. 81, No. 915, 1988

L SALNAIS,Boeing Canada, de Havilland Division, Downsview, Ontario

Aluminum alloy structural components for aircraft designed prior to the early 1970s, were machined from 2024, 7075 and 7079 plate, bar and forgings in either the T3xxx of the T6xxx tempers. Protective treatments for these parts consisted of chromic acid anodizing and alkyd zinc chromate primer, plus a nitrocellulose lacquer for exterior parts. The major service problem with these parts was the frequent occurrence of exfoliation corrosion and stress corrosion cracking (S.C.C.). Therefore, 2024 and 7079 alloys, with minor exceptions, were not used in aircraft designed after the early 1970s. Replacement materials were 7075 and 7050 alloys in the averaged, exfoliation corrosion and S.C.C. resistant, T73xxx tempers. The use of improved materials together with the upgrading to chromated epoxy primers, polyurethane enamels and the introduction of water displacing corrosion inhibiting compounds have significantly reduced corrosion in aircraft.
Keywords: Materials engineering, Corrosion, Metallurgy, Coatings, Aerospace materials, Metals.