ASTM D4541-02 pdf free.Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers.
ASTM D4541 covers a procedure for evaluating the pull-off strength (commonly referred to as adhesion) of a coating system from metal substrates. Pull-off strength of coatings from concrete is described in Test Method D7234. This test offers two test protocols. Protocol 1 (test to fracture) determines the greatest perpendicular force (in tension) that a surface area can bear before a plug of material is detached. Protocol 2 (pass/fail) determines if the coated surface remains intact at a defined load criteria. Fracture will occur along the weakest plane within the system comprised of the test fixture, glue, coating system, and substrate, and will be exposed by the fracture surface. ASTM D4541 maximizes tensile stress as compared to the shear stress applied by other methods, such as scratch or knife adhesion, and results may not be comparable.
3. Summary of Test Method
3.1 The general pull-off test is performed by securing a loading fixture (dolly, stud) normal (perpendicular) to the surface of the coating with an adhesive. After the adhesive is cured, a testing apparatus is attached to the loading fixture and aligned to apply tension normal to the test surface. The force applied to the loading fixture is then gradually increased and monitored until either a plug of material is detached, or a specified value is reached. When a plug of material is detached. the exposed surface represents the plane of limiting strength within the system. The nature of the failure is qualified in accordance with the percent of adhesive and cohesive failures and the actual interfaces and layers involved. The pull-off strength is computed based on the maximum indicated load the instrument calibration data. and the original surface area stressed.
6. Test Preparation
6.1 The method for selecting the coating sites to be prepared for testing depends upon the objectives of the test and agreements between the contracting parties. There are, how ever, a few physical restrictions imposed by the general method and apparatus. The following requirements apply to all site.
6.1.1 The selected test area must be a flat surface large enough to accommodate the specified number of replicate tests. The surface may have any orientation with reference to gravitational pull. Each test site must be separated by at least le distance needed to accommodate the detaching apparatus The size of a test site is essentially that of the secured loading fixture. At least three replications are usually required in order to statistically characterize the test area.
6.1.2 The selected test areas must also have enough perpen dicular and radial clearance to accommodate the apparatus, be flat enough to permit alignment, and be rigid enough to support the counter force, It should be noted that measurements close to an edge may not be representative of the coating as a whole.ASTM D4541-17 pdf free download.