| 摘要 |
PROBLEM TO BE SOLVED: To easily and surely preserve again respective surfaces having their plated layers cut off by machining, by forming paraffin layers on the inner/outer surfaces of a gas cock body made of cast iron casting. SOLUTION: This gas cock body is manufactured by cast iron, so that its surface 10a and the inner surface 10b have casting surfaces and a screw cylinder part inner circumferential face and a screw part are not formed yet. The whole body in this state is dipped into molten zinc for rust prevention and the surface 10a and the inner surface 10b, whole areas are coated with a zinc-plating layer 1. Then, the constitutional wall surface of a cock storage part 11, opening ends 15a, 16a of the screw cylinder, and top/bottom surfaces of a flange 17 requiring the accuracy and sealing performance are machined to be finished into smooth surfaces and formed into the screw parts 15b, 16b. Because the machined surface 19 with have the plating layer 1 cut off, the whole body is dipped into molten paraffin to form a thin paraffin layer 2. This constitution can prevent the surface with plating layer from rusting and prolong the service life of the parts with the plating layer because of its being protected thereby.
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