Abstract: The surfaces of CT4 alloy,an advanced internal-combustion-engine material,were modified by micro-arc oxidization(MAO).The influence of the oxidation time on the microstructures and corrosion resistance of the modified TC4 alloy was investigated with X-ray diffraction,energy dispersive spectroscopy,scanning electron microscopy and electrochemical station.The results show that the oxidation time had a major impact.For example,as the oxidation-time increased,the thickness of MAO coatings increased,accompanied by formation of “crater-shaped” pores and cracks,and the self-corrosion potential,higher than that of CT4 alloy,increased.Dominating rutile-phased TiO₂ and some anatase-phased TiO₂ coexisted in the MAO coatings; a loose porous surface layer covered the bumpy,compact bottom layer on top of the rough porous interface.Besides,the MAO coatings coupled with electrode of N80 steel significantly improved the corrosion resistance of N80 steel.