Method for preparing zinc-aluminum-magnesium alloy coating based on dual-plating method

The invention discloses a method for preparing a zinc-aluminum-magnesium alloy coating based on a dual-plating method, and belongs to the technical field of metal material surface heat treatment. The method comprises the steps that firstly, a metal matrix is subjected to pretreatment such as finishing, degreasing, acid washing and water washing; and secondly, the pretreated metal matrix is subjected to pure zinc hot dipping treatment in the presence of a plating assistant and then subjected to hot dipping treatment in a zinc-aluminum-magnesium alloy solution, so that the zinc-aluminum-magnesium alloy coating is prepared on the surface of the metal matrix. The method has the advantages of short process time and low aluminum content and magnesium content, and the zinc-aluminum-magnesium alloy coating which is stable, uniform, moderate in thickness, good in surface gloss and neatness and good in bending resistance is formed by adopting a refining agent for slagging and an air cooling mode for cooling. The prepar