Mapping the initial corrosion activity of aluminium alloy 2024-T3 in diluted substitute ocean water by localized electrochemical impedance spectroscopy

Abstract

This work deals with the initial localized corrosion activity of AA2024-T3 exposed up to 24 h in diluted substitute ocean water, simulating marine environment of low chloride contamination. The pits appeared since the first hour at the periphery of CuFeMn particles and Mg-ions release was found to be 0.5 mg L, originated from the S-phase (AlCuMg). Fine particles were detached from the corrosion layer, composed of AlCl· 6HO and FeCl· 2HO corrosion products. Localized electrochemical impedance spectroscopy (LEIS) measurements were performed in situ at open circuit potential. LEIS maps revealed intensive electrochemical activity on Al alloy surface since the first hour, demonstrating fast pit nucleation, due to the presence of chloride ions. LEIS impedance │Z│ magnitude differs with the advance of the corrosion process, influenced by changes occurring on the alloy surface. The reported results confirm the unique capabilities of LEIS that make this a powerful tool for in situ study of localized corrosion process.