| 摘要 |
PURPOSE:To form a high-quality coat of resin by sandblasting a raw steel pipe, and spraying a chemical conversion coating soln. to remove dust before the pipe is externally coated with the resin. CONSTITUTION:An incoming steel pipe 1 is sandblasted by a sandblasting device 10, and a chemical conversion coating soln. is then sprayed from the nozzle holes 2a of a ring nozzle 2. At this time, the spraying pressure against the steel pipe surface is controlled to about 0.2-5kg/cm<2>, and the amt. of the soln. to be spraying is adjusted to about 1-20l/m<2>. A chromating soln. etc., are used as the chemical conversion coating soln. The sprayed chemical conversion coating soln. is received by a receiving tank 3, and the dust contained in the soln. is removed by a magnetic separator 4. The soln. is then circulated by a pump 6 through a pipeline 9 and a filter 5, and the chemical conversion coating soln. is supplied to the receiving tank 3 from a feeder 11. The chemical conversion-treated steel pipe 1 is sent to a resing coating stage A through a squeeze device 7 (polyurethane, etc.), heated by a preheater 8 to form a chemical conversion coated film, and then coated with a resin.
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