Abstract
A method for evaluating the interfacial adhesion strength between paint layer and chromate-coated steel sheet were proposed. The adhesion strength was evaluated by the critical strain energy release rate at interfacial crack initiation. To measure the critical strain energy release rate, an End Notched Flexure specimen was used, where an interfacial pre-crack was induced between the paint layer and steel sheet. Two kinds of the steel sheets modified with chromic acid which contained colloidal silica or not were used to measure the critical strain energy release rate. Cohesive interfacial fracture was hardly observed for the both steel sheets. It was observed that the energy release rate increased with the colloidal silica included in the chromate-coated steel sheet. Similar dependency of the silica content on the adhesion strength had been also confirmed in the cross cut tests. This signifies that the interfacial adhesion strength can be evaluated quantitatively by the critical energy release rate.
