Q: We currently purchase a prepainted white panel (liquid application) over galvanized steel and galvanized posts that also has a paint coat. The paint coat on the post is a polyester powder coat, and the liquid coat on the panels is a polyester. The problem is the surface energy on the posts seems to be significantly lower, as we have decals that are lifting off the posts and not on the panels.
Would this be considered an effect of the powder coat finish? Is there any way to correct this?
Whatever advice you can throw my way would be most appreciated.
A: This is not an uncommon phenomenon. Some powder coatings have low surface energy, while others have higher surface energy.
The basic issue has to do with the additives contained in the formula. Some formulators like to incorporate waxes and even Teflon to increase scratch resistance. This unwitting formulating technique makes it nearly impossible for anything to adhere to the powder.
You have a couple avenues to consider in remediating this problem. You can sometimes perform a rigorous surface cleaning using a solvent (acetone, lacquer thinner), which will make the powder coating surface more amenable to decal adhesion. You can also consider mechanical means of “cleaning” the surface (e.g., light sanding).
The best avenue is to get a different powder coating – one that has been formulated to provide good topcoat and decal adhesion. Your powder supplier should be able to test their product with your decals to verify this property.