A Comparison of the Corrosion Behavior of Several Nanocrystalline and Conventional Coarse Grain Al 5083 Samples

The corrosion behavior of nanocrystalline and conventional Al 5083 was compared in solutions of different chloride concentrations. Bimodal samples which were made from a blend of nanocrystalline and coarse grain powders were also tested. Pitting scan (PS) and electrochemical impedance spectroscopy (EIS) have been used to evaluate the susceptibility of the samples to pitting. The nitric acid mass loss test (NAMLT) has been used to assess their intergranular corrosion susceptibility. All samples pitted at their corrosion potential (Ecorr) when exposed to 0.5 N NaCl; as the Cl- concentration decreased, higher pitting potentials (Epit) and passivation behavior were observed. The analysis of EIS data obtained in 0.5 N NaCl showed that the samples had similar tendencies in terms of pit growth rates. The results of the NAMLT showed that nanocrystalline and bimodal samples were not susceptible to intergranular corrosion, while grain boundary attack was observed for the conventional Al 5083.