Plating method of low-aluminum hot-dipped Zn-Al-Mg-Si alloy coating

The invention discloses a plating method of a low-aluminum hot-dipped Zn-Al-Mg-Si alloy coating. By the use of an electrolytic activation plating auxiliary, a layer of compact and uniform grey black salt film can be formed on the surface of a protected base material. Thus, the problem that a general plating auxiliary fails when aluminium content is high during hot galvanizing and plating leakage and unevenness happen to the surface of a coating can be solved. By means of a scanning electron microscope and a salt spray test chamber, a microscopic structure and corrosion resistance of a Zn-Al-Mg-Si alloy coating in different composition proportions are measured. It shows through results that a coarse Zn-rich phase can be refined and the structure can be homogenized after proper amounts of Al, Mg and Si are added. Corrosion resistance of the hot-dipped Zn-2%Al-1.5%Mg-0.15%Si alloy coating obtained by the above technological method is optimal.