Investigation of the electrochemical behaviour of AA1050 aluminium alloy in aqueous alkaline solutions using Dynamic Electrochemical Impedance Spectroscopy

The paper presents the electrochemical behaviour of aluminium alloy AA1050 in aqueous alkaline media in the pH range 14-85. Electrochemical study was applied in order to obtain comprehensive information on the mechanism and kinetics of the process of anodic dissolution of aluminium, supplemented by monitoring of surface topography using an electron microscope. The corrosion rate of AA1050 increases with increasing concentration of hydroxyl ions OH-. Cathodic reaction occurs in the form of two competing processes, oxygen depolarization and hydrogen evolution. During anodic polarization process up to +8 V vs Ag vertical bar Ag2O, activation control of the electrochemical process is converted to diffusion control upon reaching the potential approx. 0 V. Instantaneous impedance spectra in Nyquist projection had at least two time constants: high-frequency loop of capacitive character associated with charge transfer process during anodic dissolution and negative low-frequency capacitance loop. Dynainic processes occurring during anodic dissolution of aluminium alloy can be concluded on the base of instantaneous change of electric parameters. Dynamic Electrochemical Impedance Spectroscopy (DEIS) enables continuous impedance monitoring of non-stationary processes, such as anodic dissolution of aluminium in aqueous alkaline environments. (C) 2016 Elsevier B.V. All rights reserved.