The desmutting of 2024-T3 aluminium alloy using a new rare earth desmutting solution has been studied by SEM and X-ray photoelectron spectroscopy (XPS). It was evident from SEM that, during desmutting, there was dissolution and etching of both the intermetallics and the basic oxide scale left after alkaline cleaning. In addition, copper from the intermetallics was deposited as a residue on the surface of the desmutted alloy. The residue, in the form of precipitates ~200 nm in size, proved to be copper with an oxide coating. The addition of oxidants such as hydrogen peroxide (H2O2) and potassium persulphate (K2S2O8) removed these precipitates. It was apparent from XPS that the surface was coated with a thin 6 nm aluminium oxide after desmutting.