TWO-LAYER PLATING STEEL SHEET OF ZINC AND ZN-MN ALLOY WITH AN EXCELLANT ADHESION AND CORROSION RESISTANCE AND PROCESS THEREFOR

摘要

The steel sheet comprises a lower Zn layer and an upper Mn-Zn alloy layer deposited on the lower layer. The plating method comprises; evacuating the vacuum chamber to less than 1 x 10-5 torr; blowing Ar gas in the vacuum chamber; cleaning the substrate by electric discharge method supplying the negative voltage of 500-1000 V; heating the substrate in a range of room temp. to 250 deg.C; degassing the vaporising sources by introducing a current; vacuum depositing the Zn onto the substrate in the region of the deposition amt. of 1-10 g/m2 by opening the covered shutter of the Zn vaporising source; and vacuum depositing the Mn-Zn alloy onto the Zn deposited layer in the region of the deposition amt. of 20-40 g/m2 by opening the covered shutter of the Mn vaporising source. The steel sheet has excellent adhesion property and corrosion resistance.