Corrosion protection performance of sol–gel coatings doped with red mud applied on AA2024-T3

Abstract

This paper studies the effect of 5wt% red mud particles addition to sol–gel films applied on AA2024-T3 aluminium alloy. The red mud powder was dried or calcined, previously to added to the sol–gel film, in order to analyzed the effect of the thermal activation. The RM particles were characterized using several techniques; x-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results confirm that the thermal treatment leads to several phase transformations which affect to gibbsite, Al(OH)3, boehmite, AlO(OH), and goethite, FeO(OH), species.The anti-corrosion properties were evaluated by salt pray test and electrochemical impedance spectroscopy (EIS) techniques. Both types of studies indicate increased protecting properties of the sol–gel films doped with calcined red mud particles. Although the inhibition mechanism is not well-established, it must be related to the formation of reactive species during the heat treatment, which can evolve to mixed aluminium oxides in contact with the electrolyte.