| 摘要 |
PROBLEM TO BE SOLVED: To provide a protective-multilayer-coated steel pipe having a multilayered, protective surface coating layer which is formed on the surface of a steel pipe without using harmful hexavalent chromium or the like, while having adhesiveness and corrosion resistance equal to better than a conventional chromate film. SOLUTION: The protective-multilayer-coated steel pipe has an electrogalvanized layer formed on the outer surface of a steel pipe, a zinc phosphate film layer with a thickness of 0.01-2μm formed on the electrogalvanized layer through electrolysis, and a synthetic resin layer formed on the zinc phosphate film layer by coating or extrusion. COPYRIGHT: (C)2004,JPO&NCIPI
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