| 摘要 |
PROBLEM TO BE SOLVED: To clear the structural concrete requirements of a chromate-free chemical conversion coating capable of obtaining excellent corrosion resistance, and to provide a surface treated steel sheet having excellent corrosion resistance equal to that of the conventional chromate treated steel sheet though it is free from chromate. SOLUTION: In the surface treated steel sheet obtained by coating the surface of a galvanized steel sheet with a Cr-free coating, the surface of the galvanizing film is provided with a compound layer comprising each element of P, Zn and O and further comprising one or more kinds of elements selected from Mn, Mg and Al, the upper layer thereof is provided with a silica-concentrated layer, and the upper layer thereof is further provided with an organic resin layer. Preferably, the space between the compound layer and the silica-concentrated layer is provided with a P-concentrated part which does not accompany the concentration of Zn, Mn, Mg and Al. COPYRIGHT: (C)2005,JPO&NCIPI
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