Effects of fluoride on the structure and properties of microarc oxidation coating on aluminium alloy

The composition of electrolyte plays a key role in the structure and properties of the synthesized ceramic coating by microarc oxidation (MAO) process. In the present study, F− ion, the smallest size among the negative ions, is chosen as the additive. The effects of F− ion on the structure and properties of the formed ceramic coating have been investigated in detail. Inspection of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) suggests that the addition of fluoride during MAO process can decrease the porosity of the surface and enhance the density of the coating. These structure features lead to the corrosion resistances and tribological properties greatly improved. Based on the experimental results and the characteristics of MAO process, the influence mechanism of F− is proposed.