HOW TO TEST PAINT ADHESION BY PERFORMING AN ADHESION TEST.
Can I paint over the existing coating is a question Rustbuster are asked nearly every day, it can depend on several things?
- Condition of the existing paint system
- Whether the existing coating system can be over coated?
- Is the existing paint system stuck well enough to accept another coat of paint?
Well let’s assume that the previous coating is visually in decent condition and that it can be overcoated so how do we check that it’s well stuck?
Detailed below are instructions on how to perform a Cross Hatch Coating Adhesion Test.
You’ll need a sharp knife (Of the Stanley type not one from the kitchen) and some cellotape/strong packaging tape and if ones handy a ruler/straight edge always helps.
1) Select a small area on the substrate to be coated, remove all dirt, grime, debris and any other surface contamination.
2) Cut 5 vertical lines (approx. 1mm apart) into the surface of the existing paint on the substrate.
3) Cut 5 horizontal lines approx. 1mm apart) over the vertical lines. This will leave a checkerboard effect.
4) Apply a piece of cellotape/packaging tape to the cut area and apply pressure to allow this to stick to the surface.
5) Pull away the tape from the surface with some speed.
6) If no paint comes off with the tape then adhesion is good in this area, if multiple squares come away from the surface then the coating isn’t adhering correctly to the substrate.
7) It’s always best to perform this test in multiple areas to get an overall idea of coating adhesion.
Getting proper adhesion is vitally important if you intend for the new paint system you have applied to last, you wouldn’t paint over a greasy surface would you?
Todays paints dry and cure by several mechanisms but whilst drying all exert pressure onto the previous coatings, if these previous coatings are not adhered correct your new system will fail.