Compound ceramic coatings on TC4 alloy were prepared by pulsed bi-polar micro-plasma oxidation in NaAlO_2 solution.The phase composition and morphology of the coatings and the effects of the coatings on the acid corrosion resistance of TC4 were studied. Results show that the ceramic coating is composed of Al_2TiO_5,α-Al_2O_3 and rutile TiO_2.The coating is composed of compact inner layer and loose outer layer.The galvanic corrosion resistance of the coated samples coupled with LY12 aluminum alloy and H62 ye...