A microstructural investigation on the corrosion behavior of friction stir welded AA2024 aluminium alloy welds

In this research, the corrosion behaviour of friction stir welded AA2024 aluminium alloy immersed in NaCl solution with different pH values, Chloride ion concentration and immersion times have been investigated using immersion corrosion tests. In addition, an empirical relationship was established to predict the corrosion rate of friction stir welds of AA2024 aluminium alloy. The microstructural characterization was done using light optical microscopy and scanning electron microscopy. It was resulted that the pitting was observed on the weld surface. The pits are more aggressive in higher chloride ion concentrations. With the increase in exposure time, the depth of the corrosion pit stops increasing as the pit bottom becomes passive, but general corrosion still brushes away the top layer of the bulk material. Furthermore, the damage caused by this type of corrosion is accentuated in solutions of acidic pH comparing to slightly neutral solution, suggesting that the anodic activity of the system became intense with this acid range of pH. Exposure to solution of alkaline pH results in more intense corrosion attack. Copyright © 2014 American Scientific Publishers All rights reserved.