Sumitomo Metal Industries, Inc.

Hiroo Maeda

Masashi Yamamoto

Tamotsu Toki

Toshio Nakamori

Mutsuo Sagara

Hirohito Masumoto

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.degree. 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.

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Kitakyushu, Japan

Hiroo Maeda