Resistance to Pit Formation and Pit Growth for Different Tempers of AA2024 Aluminium Alloy in Presence of Benzotriazole

Abstract

The paper analyses the corrosion behaviour of both naturally and artificially aged AA2024 aluminium alloy in NaCl solution in the presence of the corrosion inhibitor benzotriazole (BTA). The differences between these two aging tempers in terms of resistance to general corrosion are explained as well as the differences in terms of pit formation and pit growth. Based on the values of the polarisation resistance and the corrosion current density, the general corrosion resistance of the alloy is determined in the absence and in the presence of BTA. The resistance to pit formation and pit growth is determined on the basis of the polarisation measurements results. Scanning electron microscopy confirmed the expected differences in the appearance and size of the pits formed in naturally aged and artificially aged alloy. In the presence of the corrosion inhibitor BTA, for both aging tempers of the alloy, the corrosion resistance is significantly higher compared to the resistance in the solution without the inhibitor. The value of the polarisation resistance for both aging tempers increases over time. However, at the same time, the value of the constant phase element increases as well. An explanation for this phenomenon is provided. The calculated average value of the thickness of the adsorbed inhibitor layer on the surface of the aluminium alloy is in accordance with the inhibitor protective ability for both aging tempers.