Preparation of a novel yellow ceramic coating on Ti alloys by plasma electrolytic oxidation

A novel yellow ceramic coating on Ti alloys was prepared by plasma electrolytic oxidation technique in this paper. The influences of the concentration of phosphate on the color and the structure of the coatings were investigated. The structure and the composition of the coatings were studied by XRD, SEM and XPS, respectively. The results show that the porous coatings with different colors are composed of rutile TiO2 and anatase TiO2. The yellow coatings' thickness is around 10 μm and the roughness is 0.6 μm or so. The large amount of V in the yellow coating determines the color in the form of sodium vanadate and sodium vanadite. The calcination test shows that such yellow coating has good thermal stability in color under 100 °C while the color deteriorates under 200 °C.