Effect of pulse frequency on microstructure and surface properties of Ck45 steel treated by plasma electrolysis method

► EPP cleaning within 150-200 V markedly reduced the surface roughness of the Ck45. ► Coating contained Fe3O4 was attained within 300-350 V during plasma electrolysis. ► Raising the frequency resulted in reduced surface roughness of the oxide layers. ► Increasing the frequency resulted in improved corrosion behaviour of the surface. ► Increasing the frequency resulted in the thicker oxide coating.