INTERGRANULAR CORROSION MORPHOLOGY AND GROWTH KINETICS IN HIGH STRENGTH ALUMINUM ALLOYS

摘要

The growth kinetics and morphology of intergranular corrosion (IGC) in 7xxx Al alloys was studied by several different techniques. Samples corroded potentiostatically in NaCl solution developed a morphology that combined sharp IGC and selective grain attack. Samples encased in epoxy except for one face were found to develop sharp intergranular fissures during subsequent exposure to high humidity conditions. Properly oriented and unconstrained samples (free standing and not epoxy-encased) developed exfoliation corrosion (EFC) during exposure to high humidity after a potentiostatic pretreatment in NaCl solution. A new technique, Exfoliation of Slices in Humidity (ESH), was developed for the determination of EFC susceptibility and quantification of EFC kinetics.