A spectroscopic and microstructural study of oxide coatings produced on a Ti-6Al-4V alloy by plasma electrolytic oxidation

► PEO (plasma electrolytic oxidation) for production of oxide coatings on a Ti-6Al-4V alloy. ► Two different current modes namely pulsed unipolar and bipolar was used. ► Optical emission spectroscopy (OES) was used to characterize the PEO plasma. ► This is the first attempt to characterize spectroscopically the PEO plasma of Ti and its alloys. ► The discharge behavior effect on the formation and structure of the coating was determined.