H. Mindivan, M. Baydogan, E. S. Kayali, H. Cimenoglu, Istanbul Technical University, Istanbul, Turkey

Summary:

Aluminum alloys are outstanding materials for aerospace industry due to the excellent combination of strength and density accompanied by good corrosion resistance. However, corrosive environments such as exhaust gases, moistore, waste water, and spillage encourage mostly intergranular corrosion and stress corrosion cracking on an aerospace structure. Intergranular corrosion which exhibits itself by lifting up the surface of a metal by force of expanding corrosion product accumulating at grain boundaries just below the surface. Stress corrosion cracking which results in failure by cracking under combined action of corrosion stress may be either intergranular or transgranular. Considerable efforts have being made for further improvement of corrosion resistance of aluminium alloys.

In this study, the effect of aging procedure on intergranular corrosion (IGC), stress corrosion cracking (SCC) and cavitation erosion corrosion (CEC) behaviour of 7039 aluminum alloy has been evaluated. The alloy was tested in two different aged conditions, namely T6 and retrogression and reaging (RRA), in a “30g/l NaCl + 10ml/l HCl” solution. The experimental results showed that the RRA treatment, which yielded almost similar IGC resistance with that of T6 treatment, considerably improved the SCC and CEC resistances of the alloy without sacrificing the hardness.