Composite metal sheet and method for producing it

摘要

Disclosed is a composite metal sheet to be produced by chemically treating the surface of a metal substrate, coating and drying an organic resin-based composition thereon to form a undercoat layer, then coating thereon a two-layered resin interlayer composed of an adhesive layer of a modified polyolefin resin and a polyolefin resin layer at a thickness of from 50 to 300 mu m, then modifying the surface of said polyolefin resin layer by flame treatment or corona discharging treatment thereby forming functional groups in an amount of from 0.05 to 0.30 in terms of O/C representing the ratio of the amount of oxygens in the functional groups to the amount of carbons on the surface, and finally coating and drying an urethane-curing polyester resin paint or an urethane-curing fluorine resin paint at a thickness of from 8 to 35 mu m to form a top coat layer. The composite metal sheet has excellent corrosion resistance, weather resistance and formability.