What the significance of adhesion testing in paints and coatings?
What are the different test methods for adhesion testing?
Good adhesion is critical to the integrity and long-term performance of a coating. Poor adhesion can result in failure, corrosion and contamination of surfaces or contents. So, it’s vitally important to undertake adhesion testing to assess the quality of the attachment between the dry paint film (coating) and its substrate.
Pull-off Test — This procedure is accomplished by sticking a loading fixture perpendicularly to the coating, then slowly increasing tensile load until either the fixture and adhesive layers are removed or until a predetermined value is reached.
Knife Test — This procedure is accomplished by making two cuts into the coating with a utility knife to form an “X” shape. The coating is then lifted at the vertex, using the point of the knife.
Scrape Test — This procedure is accomplished by loading a rounded stylus or loop onto a balanced beam scrape adhesion tester at a 45-degree angle, then increasing the load until the stylus removes the coating from the surface of the substrate
Tape Test — This procedure is accomplished by cutting either an X shape (method A) or a lattice pattern (method B) into the coating, then applying pressure sensitive over the cuts and removing.