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Abstract:
7xxx series aluminum alloys (Al-Zn-Mg-Cu) have been widely used in recent decades in aerospace applications because of their high strength and low density. However, these alloys are susceptible to various forms of localized corrosion such as exfoliation corrosion (EC), intergranular corrosion (IC) and stress corrosion cracking (SCC). In order to evaluate the corrosion behavior of the alloys various laboratory accelerated corrosion tests have been developed, which, useful though they may be, are nonetheless unable to simulate the actual corrosive environment and reveal the actual mechanism of corrosion. In this work the progress of corrosion of solution heat treated, aged and overaged AA7075 aluminum alloy specimens was studied systematically by using a controlled humidity chamber that is a milder environment than that of laboratory tests and thus closer to operating conditions. The systematic study of the specimens indicated that the corrosion behavior improved with heat treatment of aging and overaging, while the mechanism of corrosion starts as pitting and progresses as intergranular corrosion.
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