Adhesion

The adhesion of a coating on a substrate is crucial for the mechanical performance as well as for the corrosion protection. In practice, there are several test procedures for determining the adhesion such as cross-cut test, mandrel test and impact test.

Cross-cut test

The cross-cut test is a very rapid and simple method for the assessment of single and multi-coat systems. Here, cuts in a 30° angle (method A) or right-angle (method B) are executed so that you receive a lattice pattern or an X-shape. These test methods can be used as quick pass/fail tests. When applied to a multi-coat system, assessment of the adhesion of individual layers of the coating among each other may be carried out.

Bend test

Mandrel testers are common test apparatuses used for the determination of the elongation/and adhesion of coatings at bending stress. At a bend test a test panel is bend over a certain radius.

Conical mandrel testers bend the test panels over a conus so that a large variety of bending radii is tested at the same time.

The cylindrical mandrel test can be carried out as a quick pass/fail test with a single mandrel of specified diameter or as repeated procedure with decreasing mandrel diameters for determining the diameter of the first mandrel causing failure.

Impact test

Impact tests are a test method for evaluating the resistance of a dry film of paint, varnish or related product to cracking or peeling from a substrate when it is subjected to a deformation caused by a falling weight dropped under standard conditions.