| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zinc-aluminum alloy plated rectangular steel tube excellent in adhesive properties and moisture resisting durability and capable of adhesion even to dissimilar materials. SOLUTION: As to this zinc-aluminum alloy plated rectangular steel tube, a film of a water base resin compsn. contg., as indispensable components, (A) water base emulsion of a polyurethane resin having 60 to 100 deg.C glass transition temp. and 20 to 40 KOH mg/g acid value, (B) water base emulsion of a bisphenol A type epoxy resin having >= two epoxy groups in one molecule, in which the equivalent of epoxy is controlled to 180 to 280 and (C) colloidal silica, and in which, to 100 pts.wt. polyurethane resin (A), the epoxy resin (B) is blended by 2 to 5 pts.wt., and, to the total weight of (A)+(B), 15 to 30 pts.wt. colloidal silica (C) is blended is formed on the outer surface preferably by 1 to 10 g/m2 coating weight.
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