PURPOSE: To easily and stably form a high-quality plating film by previously subjecting steel products to a heating treatment in a gaseous fluorine atmosphere to remove the oxides on the surface of the steel products and to activate the surfaces at the time of plating the steel products.
CONSTITUTION: The steel products 24 to be plated are disposed in a furnace body 20 partitioned from a pot furnace 25 contg. a molten metal 27 for plating, such as molten 2n or molten Al, by a sliding door 22. While the steel products are heated to a high temp. by a heater 21 in the furnace body 25, gaseous fluorine system, as F2 or CF4, is introduced from an upper introducing port 23 into the furnace. The SiOx oxides and MnOx oxides formed on the surface are removed and the fluoride films are formed at the time of annealing of the steel products 24. The sliding door 22 is then opened and the steel products are immersed into the bath 27 of a plating metal, such as molten Zn. The fluoride films on the surfaces of the steel products are easily removed by the flux on the surface of the plating bath 27. The high-quality molten metal plating film which is free from unequal plating and appearance defects is formed by the plating metal bath 27 in the activated state without having the oxide films, etc.
TAWARA MASAAKI
SENBOKUTANI HARUO
KITANO KENZO
