Electrochemical behaviour of a Mg-rich primer in the protection of Al alloys

The electrochemical behaviour of Mg-rich primer on Al Alloys, AA2024 and AA7075, has been studied via Electrochemical Impedance Spectroscopy (EIS), Open Circuit Potential (OCP) and potentiodynamic polarization. Results showed that the Mg-rich primer provides sacrificial protection to the Al substrate by a two-stage mechanism. In a first stage, corrosion of aluminium is prevented by cathodic polarization, whereas at a later stage the precipitation of a porous barrier layer of magnesium oxide was observed.