Abstract: The surfaces of Q235 steel,a water pipe material,were modified by micro arc oxidation(MAO).The influence of the oxidation time on the microstructures and tribological behavior of MAO coatings was investigated with X-ray diffraction(XRD),scanning electron microscopy(SEM) and conventional mechanical probes.The results show that the oxidation time had a major impact.To be specific,as the oxidation time increased,the thickness,compactness,surface roughness and friction coefficient of the MAO coatings increased,the growth-rate and surface porosity decreased,accompanied by an increase of the corrosion-resistance,however,the wear-rate and wear-track depth changed in a decrease-increase-decrease mode.The friction coefficient of MAO coating was large than that of Q235 steel,and the crater-shaped pores,with a fairly big size distribution,dominated the MAO coatings.Possible mechanisms were also tentatively discussed.