Torsion delamination test, a new method to quantify the adhesion of coating: Application to car coatings

A torsion delamination test was developed to characterize the interfacial cohesion of multilayer organic coatings. It consists in applying an increasing torque on a hexagonal plot directly glued on the coating until delamination occurs. The test is quantitative and allows the calculus of the shear stress that generates delamination. This torsion test was successfully used to test the adhesion of multilayer car coatings. The delaminating interfaces were directly observed via optical and electron microscopy. We have shown that the critical delaminating shear stress and the delaminating interface are dependent of both the primer and of the curing temperatures respectively. Furthermore, an interpretation of the delamination process is proposed.