Powder Coating Coating Adhesion Detection Methods And Devices

At present, the main coating test methods are tensile test, shear test, indentation test, scratch test and so on, but due to their limits, these methods are not suitable for the evaluation of the bonding strength between the thick coating layer and the substrate. So far, there isn't an authority standard to evaluate the thick coating layers' bonding strength. There are three necessary qualifications to estimate an efficient test now. Having researched current test methods, the fourth qualification was brought forward in this paper, that is, the test sample should be designed to satisfy the practical boundary conditions (namely, there is a free surface on the test sample). Otherwise, not only was the veracity of the measure affected, but also the destroy mode in the practice would be changed.Aiming at the characteristic of the powder coating and the failure form—bulge-peel form ,which usually happens in the practice, a sort of new test method—bulge-peel test and the corresponding equipment were developed in this paper.The entire structure of the test equipment was mainly designed. The functions of each composing system and the selected principles of the apparatus were introduced in detail, and the key parts were designed through calculating strictly. Especially, the dimension of the hole in the sample was calculated approximately through the small-strain-flat theory, which is simple and direct, and can meet the test requirement.The principle, characteristic, function and the data processing method of the bulge-peel test were explained entirely, and two new parameters—the line peel-off intensity and the plane peel-off intensity were firstly introduced to estimate the bonding strength between the thick coating and the substrate. By modeling, the formulas for calculating the line peel-off intensity and the plane peel-off intensity were deduced, and the standard to estimate the bonding strength was put forward.Using finite element software—ANSYS, the bulge-peel test can be analyzed with Finite Element Method (FEM). The finite element model was created and the boundary condition and the force condition were loaded. The bulge-peel test could gain the stress results after solution. By analyzing the list of results, the parameter r—the peel-off ring radius and the parameter b—the peel-off ring width could be confirmed.In order to validate the feasibility of the bulge-peel test and equipment, and explain the important role of FEM during the processing and analyzing the test data, one group of experiments were carried out.