Abstract:The corrosion behaviours of naturally aged and artificially aged AA2024 aluminium alloys in 0.5 mol/dm³ NaCl solution in the presence of environmentally friendly corrosion inhibitors of 10 mmol/dm³ CeCl₃, 10 mmol/dm³ BTA and the inhibitor mixture (5 mmol/dm³ CeCl₃ + 5 mmol/dm³ BTA) were analyzed. The goal of this work was to determine the level of the synergistic effect of the inhibitor mixture and to explain the nature of this effect. Corrosion properties of the inhibitor layer were studied using the electrochemical impedance spectroscopy (EIS), while the resistance to pit formation and pit growth was studied by applying potentiodynamic polarisation tests. The results of scanning electron microscopy (SEM/EDS) showed that the size of pits formed in naturally aged aluminium alloy was smaller than that formed in artificially aged alloy. The synergistic effect of the inhibitor mixture on corrosion properties of naturally aged alloy was observed throughout 96 h, and in later phases of testing of artificially aged alloy. The synergistic effect of the inhibitor mixture was not noticed on pit formation and pit growth.

Key words: aluminium alloy; pitting corrosion; corrosion inhibitor; cerium; benzotriazole