How do I check for proper adhesion, and intercoat adhesion?
Adhesion is very dependent on the cleanliness of the substrate, the appropriate selection and maintenance of pretreatment, and the proper melt and cure of the powder coating. Adhesion may be tested by several different methods. A commonly used technique is the cross hatch and tape method. In this method, crossed cuts are made through the coating. Adhesive tape is then applied to the cut coating and then removed quickly. The coating adhesion is then measured by its ability to remain on the substrate and to not be removed by the tape. Powder coatings vary in their ability to provide intercoat adhesion when recoated. Epoxy powders tend to be harder and more prone to intercoat adhesion problems, particularly if they have been over baked. On the other hand, polyesters and epoxy-polyester hybrids usually recoat well. Chemistry for recoat is also important and should be tested with your powder supplier.
