Structrure of Non-chromium Phosphate Rare Earth Conversion Coating

The phosphating film′s appearance, phase structrure, components and phosphating dynamics were studied by means of potential and current-time curves, scanning electron microscopy (SEM) and X-ray diffraction(XRD). The phosphating film was formed on 6061 aluminium alloy surface and contained Zn, Fe, P, O and chromium compound. The results showed that the block crystals in the surface film with the addition of rare earth were especially compact, and the grains were smaller. The appearance was light gray and the crystal particle arrangement was arranged in a criss-cross pattern. The main components of phosphorus film were tribasic zinc phosphate and ferric phosphate zinc. The diffraction intensity of the phosphating film with the addition of rare earth reduced obviously, and the diffraction peak was also changed to wider obviously.