There are several types of adhesion testing, covering different kind of applications. For example tests to check how a coating adhere to the surface they are applied to, would differ from tests used to measure how well 2 parts are glued together.
Types of Adhesion Testing
There are a few different types of adhesion test which are recognised internationally and across different industries.
In this test a sharp knife is used to cut an X on the surface. The angle between the legs of the X should be between 30-45 degrees, and the cut should be deep enough to reach the substrate.
Following the tip of the knife is used to remove the coating, and the coating is evaluated based on how difficult it is to remove the coating and the size of the flakes coming off.
The test is very subjective and relies a lot on the inspector’s experience.
For this test a sharp razor blade or scalpel is used to cut a X in same way as in the knife test, but instead of using the knife to remove the coating, a tape is applied and rapidly removed. The part is the inspected for removed coating and rated.
A different version of the test is where a cross hatch is cut instead of an X, the tape is added and rapidly removed, followed by an inspection and rating of how much coating is removed. For this test it is possible to get a cross hatch cutter with two blades, that way the cuts are controlled and parallel.
In both cases a standardised tape needs to be used, especially when samples are compared, it is essential same tape is used.
There is a lot of other tests that can be used on coating as well, some examples are scratch test, wear test, pull off test etc.
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