| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot-dip zinc-aluminum coating method by which hot-dip galvanizing of high aluminum content can be efficiently performed by single dipping at a low cost. SOLUTION: A pickled steel material is immersed in an aqueous solution of sodium nitrite and the iron surface from which oxide film is removed is reduced and activated. After immersion in an aqueous solution of zinc ammonium chloride and baking treatment, the material is immersed in a molten zinc-aluminum alloy bath in an inert-gas atmosphere, and the zinc on the iron surface is reduced in the molten zinc-aluminum alloy bath by means of ammonium chloride gas resultant from the melting and sublimation of adhering zinc chloride and ammonium chloride due to baking and is electrochemically bonded to form iron-zinc alloy, such as Fe5 Zn21 and Fe3 Zn10 , and then an aluminum-zinc- iron alloy layer is formed to form a zinc-aluminum alloy layer.
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