Controlling Plasma Electrolytic Oxidation of Titanium Using Current Pulses Compatible with the Duration of Microdischarges

In the plasma electrolytic oxidation (PEO) process, microdischarges are produced at the titanium surface immersed in an appropriate electrolyte by applying a voltage higher than dielectric breakdown of the oxide film. During this discharging stage, lasting between 30 and 300 µs, many species are transferred from electrolytic to surface producing the coatings. In the present work, pulses of electric current with duration of 50 µs and 100 µs were used in order to interrupt the microdischarges and, thus, control the PEO process. The effect of pulse duration, using different current densities and duty cycles, was investigated by the changes in energy consumption, in addition to the topographical, microstructural and chemical properties of the surface, in order to meet the requirements of a hypothetical surface for drug delivery from titanium implants. It was shown that surfaces treated with pulse duration of 50 µs had uniform pores and smaller mean diameters, better anatase/rutile and calcium/phosphorus ratios than those treated with pulses of 100 µs. Our results reveal that using a 50 µs current pulse, the process has lower energy consumption and more suitable properties for use in titanium implants with controlled drug delivery.