EVALUATION AND COMPARISON OF THE CORROSION SUSCEPTIBILITIES OF 7178 ALUMINUM PLATE MATERIAL OF VARIOUS TEMPERS

Plate material of 7178 aluminum alloy in the -T651 and -T7651 tempers was evaluated for resistance to exfoliation and stress corrosion. Stress corrosion susceptibility was determined using tuning fork specimens stressed in the short transverse direction and exposed to alternate immersion in 3-1/2% NaCl solution. Susceptibility to intergranular and exfoliation corrosion was determined by exposure in both acetic acid salt spray and NaCl-SO2 environments. The -T651 temper was found to be acutely susceptible to intergranular corrosion and hence exfoliation and stress corrosion cracking. The -T7651 temper is less susceptible to intergranular attack and more resistant to exfoliation and stress corrosion cracking than the -T651 temper.