Protection of aluminium foil AA8021 by molybdate-based conversion coatings

A quick method for surface treatment of aluminium foil with environment-friendly and effective molybdate-based coating was developed in this study. Aluminium foil samples were treated with molybdate-based solution. The microstructure and composition of the resulting molybdate-based conversion coatings were explored by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectric spectroscopy (XPS). We found that the molybdate-based conversion coating was composed mainly of MoO3, (MoO3)x(P2O5)y and Al2(MoO4)3 compounds. Furthermore, corrosion resistance of the treated aluminium foil was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Our results show that all of the aluminium foils with molybdate-based conversion coatings have much better corrosion resistance than bare aluminium foil. Notably, the sample treated at 40 °C exhibited the best corrosion resistance. The new method is very suitable for continuous processing.