Investigation of plasma electrolytic oxidation processes of magnesium alloy MA2-1 under pulse polarisation modes

Process of plasma electrolytic oxidation (PEO) of magnesium alloy MA2-1 in an electrolyte containing sodium hydroxide and sodium tri-polyphosphate was investigated. The use of pulse shape of polarising current in both positive and negative semi-periods significantly improved efficiency of coating deposition, which is connected with increase in number of microdischarges on the article surface and intensification of plasma chemical synthesis processes. Optimal combination of interval duration before the electric pulse and duration of the pulse itself appeared to be 6 ms and 4 ms, respectively, for positive polarising pulses and 2 ms and 6 ms, respectively, for negative ones.