DENCHAKUTOSOSEINISUGURERUJUSHITOSOKOHAN

摘要

PURPOSE:To improve electrodeposition coatability and corrosion resistance without incorporating an electrically conductive pigment and furthermore, to make it possible to perform spot welding by forming a resin film wherein a urethane resin is a main ingredient and a silane coupling agent or a colloidal silica and a specified amt. of an org. pigment fine particle are incorporated on a zinc plating layer of a steel sheet. CONSTITUTION:A resin film wherein a urethane resin is a main ingredient and a silane coupling agent or a colloidal silica and 0.01-40 wt.% org. pigment fine particle are incorporated is formed on a zinc plating layer of a steel sheet. It is pref. that the silane coupling agent is in a range of 1-40 pts.wt. based on 100 pts.wt. urethane resin and the colloidal silica is in a range of 5-80 pts.wt. based on 100 pts.wt. urethane resin. The org. pigment fine particle incorporated in the resin film has a means particle diameter of 1 mum or smaller and the amt. of adhesion of the resin film is in a range of 0.1-1.0 g/m<2>. From a practical viewpoint of providing corrosion resistance, a chromate film with an amt. of chromium adhesion of 10-150 mg/m<2> is formed as an under layer of the resin film.