Today we’re going to go over how to do a proper crosshatch adhesion test. Typically you will receive a crosshatch adhesion kit that will include the tape, the crosshatch device, and a small brush. In some cases, you will also receive a magnifying glass.
To start, you will take this Crossette device, and going down to the substrate, you’ll make a crosshatch or what I would call a tic tac toe scribe across the surface.
Once complete, you should brushoff, any of the residues.
Next, we will apply the tape over the substrate, and we’ll rub that on.
Try to remove all remaining air bubbles (If not all air bubbles, as many as possible).
Now, go ahead and rip the tape off, and take a look at the back of it to make sure that we don’t see any of the crosshatches coming out.
Now you will compare your results to the ASTM crosshatch adhesion test graph. As you can see in this ASTM chart below, there is a rating, and it goes from 5B on down with 5B being the best.
The result is a definitive number that may be assigned to the adhesive property of the coating. There may be differing readings obtained on different areas of the test panel due to varying substrate densities. The high and low range of pull-off pressure that is acceptable to meet expectations should be assigned to the adhesive value of the coating.
It is recommended that the coating be tested after initial curing as well as after long-term curing occurs. Factors such as the number of mils applied, ambient air drying, forced cured drying method, and type of coating need to be considered as to when testing should be performed.
If you get a failing test, one of the things we have to go back and look at is the cure and the other is pre-treatment. So these are some of the things we want to keep in mind when performing this test.