① spray coating and spray coating layer and the combination of the formation of the base metal is different, nickel-coated aluminum flame spray through the radiation heating chemical reaction occurs in the sandblasting rust Sa3, RZ> 50μm carbon steel surface micro-metallurgical Combination of the bottom and the working layer and the resulting "anchor hook" effect of the mechanical bonding coating, and spray bonding layer and the substrate is purely metallurgical bonding coating.