Electrochemical behaviour of a combined BTA/CeCD inhibitor system for the corrosion protection of AA 2024 in NaCl solution

摘要

AA 2024 alloys are widely used in the aeronautical industry, despite their considerable susceptibility to localized corrosion in chloride-containing environments. The galvanic couplings formed between the copper-based intermetallic precipitates and the aluminium matrix are refereed as the driving force for localized corrosion processes. In this work, an aluminium/copper galvanic coupling model, elaborated in order to simulate the Al/Cu galvanic pair of AA 2024, was studied by employing SVET. Thereby, an inhibitor system composed of benzotriazole (BTA) and cerium chloride (CeCl_3) was proved to be efficient regarding the corrosion protection of the model in NaCl-containing solutions. Further, BTA and CeCl_3 demonstrated to cooperate synergistically under certain conditions. The combined BTA-based/CeO_2 protective layer obtained on the electrode surfaces was characterized by means of ToF-SIMS. In order to confirm the relevant inhibitive properties found for the Al/Cu galvanic pair model, the inhibitor system was tested on an actual AA 2024 alloy. On the base of immersion tests carried out in corrosive solutions, the BTA/CeCl_3 inhibitor system proved to be quite promising. Finally, polarization and EIS tests were performed to evaluate the corrosion protection offered by the inhibitor system. Those analyses permitted a better comprehension of the inhibition mechanisms operating when combining BTA and CeCl_3 for the corrosion protection of AA 2024.