To provide a weldable non-chromium type blackening treated galvanized steel sheet subjected to corrosion resisting treatment instead of chromate treatment.
A galvanized steel sheet 1 is used as a base, on the surface of the galvanized steel sheet, a metal/oxide composite black film 3 contg. the metals of nickel and zinc and tie oxides of nickel and zinc and optionally contg. the hydroxides thereof is formed, moreover, on the surface, a non-chromium type rust preventive film layer 4 contg. a resin and either at least a thiocarbonyl group-contg. compd. or a vanadic compd. and optionally contg. at least one kind of a phosphoric compd. and particulate silica is formed, and, if required, as the upper layer thereof, an organic resin layer 5 optionally contg. a black pigment and/or a rust preventive pigment is applied as well.
TAKAHASHI AKIRA
MORISHITA ATSUSHI
SHIMAKURA TOSHIAKI
YAMAZOE KATSUYOSHI
NIPPON PAINT CO LTD
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