On carbon steel substrate, base coating of nickel-coated aluminium and intermediate coating of 50% Al₂O₃ + 50% Ni were prepared by means of oxyacetylene spray, and final coating of Al₂O₃ ～ M_xO_y was prepared by means of plasma spray. In the fluid consisting of 60% (mass) sulphuric acid with 60 % concentration, and 40% (mass) phosphoric ore powder, the Al₂O₃ ～ M_xO_y coating resistance to corrosion and wear, is 7.46 times as strong as 18 - 8 stainless steel and is 4.06 times as strong as 316L stainless steel.