METHOD AND APPARATUS FOR MELT PLATING

摘要

A batchwise hot dip plating method is performed by dipping a metallic material in a molten metal plating bath, following fluxing by dipping the metallic material in a bath of a fused salt flux (e.g., a mixture of cryolite and one or more alkali metal chlorides and optionally aluminum fluoride) having a melting temperature at least 5 DEG C higher than the temperature of the molten metal plating bath, which also serves to preheat the metallic material. In the case of hot dip plating with an Al-Zn alloy, particularly a Zn/55%Al/0.5-2%Si alloy, a bare spot-free plated coating having good appearance can be formed by a reduced duration of dipping in the plating bath without post-plating treatment to remove flux residues. The use of a plating tank having a cross section of a round shape such as a semicircular shape or an oblong semielliptic shape, rather than a rectangular box shape, brings about a significantly extended service life of the plating tank.