Investigation on the effect of applied current density on the morphology and corrosion properties of Titania coating produced by Plasma Electrolytic Oxidation

In this study, the microstructure and corrosion properties of titanium oxide ceramic coatings formed in a carbonate electrolyte under the influence of the key factor of the density of the coating process were investigated. Plasma electrolytic oxidation coating made at current densities of 65, 82.5 and 100 mA/cm2, 1500 Hz and 11% duty cycles over a 10 minute and on a commercial titanium surface as the substrate. The results showed that the surface morphology and corrosion properties of the coatings depend on changes in the current density. The increase in the applied current density leads to changes in morphology, from pancreatic to pancake with volcanic spans, and the average diameter of the cavities increases from about 1 micrometer to 4 micrometers, which also increases surface roughness. Changes in the current density also cause variations in the voltage and intensity of the plasma around the samples, which directly affects the intensity of the microcirculation and the thermal gradient of the oxide film and causes the anatase oxidation phase to become more rutile. The corrosion resistance of the coatings increased with increasing current density, so that the corrosion current density decreased 10 times as compared to the uncoated sample, which caused a 2.5 times increase in the thickness of the coating and was more compact. The inner layer of the coating, reducing open path to the surface of the metal and the presence of the main rutile phase were attributed.