Atmospheric Corrosion of Wrought Aluminum Alloys During a Ten-Year Period

The deterioration in mechanical properties, mass loss, and the appearance of various forms of localized corrosion are documented for the exposure of a representative group of unstressed wrought aluminum alloys at three test sites over a ten-year period. Loss of ductility is the chief form of mechanical property damage observed. Among the forms of localized corrosion observed, intergranular corrosion, which led to partial sheet delamination or exfoliation, is the most damaging to the ductility of materials. Intergranular corrosion without a strong element of orientation in the wrought direction is less damaging, though more damaging than pitting without associated intergranular attack. A study of the effect of a sacrificial cladding layer indicated that loss of ductility can be completely eliminated when 7072 alloy is clad on 3004-H36 and 7178-T6 alloys, and 1230 alloy is clad on 2024-T3 alloy.