Zinc-aluminum-magnesium weld bead anticorrosive coating, composite coating and preparation method of zinc-aluminum-magnesium weld bead anticorrosive coating

The invention provides a zinc-aluminum-magnesium weld bead anticorrosive coating, a composite coating and a preparation method thereof, and belongs to the field of coatings. The welding bead anti-corrosion coating comprises a first anti-corrosion layer which covers at least part of the surface of a zinc-aluminum-magnesium welding bead; the second anti-corrosion layer covers at least part of the surface of the first anti-corrosion layer; the third anti-corrosion layer covers at least part of the surface of the second anti-corrosion layer; wherein the melting point of the first anti-corrosion layer is larger than the melting point of the second anti-corrosion layer, and the melting point of the third anti-corrosion layer is smaller than the melting point of the first anti-corrosion layer. By controlling the melting points of the three anti-corrosion layers, elements of the three anti-corrosion layers permeate mutually, and the anti-corrosion coating has the advantages of being uniform in element, high in bindin