Assessment of corrosion behavior and stress corrosion cracking susceptibility of nanocrystalline bulk Al-Mg based alloys in chloride containing solutions

The corrosion behavior of four nano Al-Mg alloys in chloride-containing environments was evaluated in a series of experiments and compared to those of wrought 5083 aluminum. The corrosion experiments conducted ranged from electrochemical tests in chloride solutions to corrosion fatigue testing in natural seawater. In chloride solutions open to the air, the nano alloys were initially passive, but once stable pitting occurred repassivation was not achieved. The AA 5083 pitted spontaneously at the corrosion potential in all chloride-containing solutions. Nano alloys were more susceptible to IGC than AA 5083. None of the alloys showed susceptibility to exfoliation. In comparison to AA 5083, the nano alloys showed better: E_oc values, R_p values, uniform corrosion rates, cathodic reaction kinetics, and SCC resistance. More variability among the nano alloys was noted in the SCC tests and in the maximum pit depth measurements than was noted in the electrochemical testing. The nano Al-7.5Mg alloy showed better low cycle fatigue performance than AA5083 but was slightly worse than AA 5083 in high cycle fatigue.