The EDS spectrum
indicates the presence of fluorine in the Barker's reagent-formed oxide
layer, which confirms the ingress of fluoride ions through the film
fromthe electrolyte. In Fig. 1d, an opticalmicrograph showing different colour contrasts with respect to the individual grains of the alloy, when
the Barker's reagent-anodized AA5083-O surface is viewed under polarized
light, is displayed. The distinctive colour contrasts show that the
grain-distinct ridge-like features produce different orientation dependent
interference