Abstract
Sea water corrosion experiments on aluminium alloy 7010 heat treated to various conditions other than the slightly overaged state in which it is normally used, have revealed several modes of corrosion assisted cracking in the deformed surface layer that results from machining or bruising. In the underaged state the 7010 alloy exhibited extensive slip plane corrosion beneath mechanically inflicted bruises on its surface. Beneath this attack some limited intergranular penetration occurred which was sharply defined, closely following grain and subgrain boundary paths. This differed from the intergranular corrosion of the T736 condition (partially overaged) where geometric etch pitting along the boundaries continued to widen them as the cracks advanced. A second precipitation hardening aluminium alloy Hiduminium 48 was subjected to similar corrosion conditions as the 7010. This alloy, in its fully hardened condition, exhibited the same slip plane type of corrosion assisted cracking as the 7010 alloy in its underaged state.
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