Abstract: Aluminum coating on Q235 steel was treated by micro-arc oxidation ( MAO ) at various treated duration to get ceramic films with different thicknesses By using hardness tester , friction and abrasion testing machine and scanning electron microscopy , the effect of treated time on thickness , hardness , friction and wear , morphology of wear trace and the microstructure after the abrasion experiment were investigated The results indicated that the thickness and the hardness of the ceramic films increased quickly as the micro -arc oxidation time prolonged The hardness of the sample treated for 30 min was several times as high as that of the non -treated sample Under dry sliding , the width and the volume of wear trace and friction coefficient decreased , which indicate that the wear resistance increased with prolonged treated time The wear mode of the aluminum coating was crushing and filing The wear mode of the samples treated by micro -arc oxidation for 20 and 30 min was scuffing and that of the sample treated for 10 min was in between that of the aluminum coating and the samples treated for 20 and 30 min