PURPOSE: To provide the Zn-Cr-Ni-P org. composite plated steel sheet which has excellent post-working corrosion resistance, coating corrosion resistance, pitting resistance, and end face rust preventiveness and is optimum as a rust preventive steel sheet for automobile bodies. ;CONSTITUTION: The org. composite plated steel sheet having the excellent post-working corrosion resistance, coating corrosion resistance, pitting resistance, and end face rust preventiveness is constituted by having an electroplating layer of a Zn-Cr-Ni-P alloy having 2 to 18% Cr concn., 0.3 and 12% Ni concn. and over 0.5% and ≤5.0% P concn., and consisting of the balance Zn and by having a chromate layer thereon and further coating the surface thereof with an org. film. The Ni and the P fix the Cr and partly convert the alloy to an amorphous alloy if the Ni and the P are added in the specific range to the Zn-Cr alloy. The corrosion resistance of the Zn-Cr alloy is thereby improved and simultaneously the extremely dense chromate film having the excellent corrosion resistance and adhesion to the film of the org. composite plated steel sheet is formed by the presence of the Cr, the Ni and the P. The resin film and the chromate bond securely to each other if the resin film is formed thereon. The excellent performance is thus maintained over a long period of time.;COPYRIGHT: (C)1993,JPO&Japio
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