Advanced generation of green conversion coatings for aluminium alloys

Anticorrosive cerium based treatments have been proved as efficient green alternatives to those based on environmentally undesirable Cr(VI) compounds. Thus, full immersion in cerium salt solutions allows reaching similar protection level against aluminium alloys corrosion that chromates treatments. However, treatment time is too high for being considered in industrial applications. In this work, accelerated methods for obtaining cerium-rich conversion coatings on aluminium–magnesium alloys are proposed. The films developed have been characterised by SEM and EDS. These studies have revealed that the coatings have a mixed or heterogeneous nature, being composed of a layer of alumina covering the matrix, together with islands of cerium formed over the cathodic intermetallics that are present on the surface of the alloy. Furthermore, studies conducted employing electrochemical techniques indicate that the degree of protection provided by these coatings is several orders of magnitude superior to that achieved with other treatments