Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2001

Getting Good Adhesion and Toughness with a Clearcoat

Q. We have been using a clear tremclad and we don't find agressive enough. We are looking for something with better adhesion qualities. Can you recommend something?

A. For excellent toughness, durability, etc., you should consider a clear polyurethane topcoat. Here are points to consider:

• The surface must be properly prepared. Polyurethanes do not have excellent adhesion to many substrates; therefore if this technology is a viable option, you might need to scuff sand or abrade the previously painted surface. Perform a few tests to determine if the coating is performing to your requirements.
• You cannot apply the polyurethane to a freshly painted surface unless you have confirmed that the two coatings are compatible with each other. Perform a few tests to determine if the coating is performing to your requirements.
• When using polyurethane coatings please give serious consideration to the following:
  • Thoroughly read the paint vendors' instructions before commencing the job.
  • Read all of the HEALTH & SAFETY instructions for the spray gun and coatings BEFORE you commence work!
  • Wear a NIOSH approved respirator specifically designed for polyurethanes
  • Do NOT apply the polyurethanes while people are in the work area. Preferably do the job over a weekend or at night to prevent others from inhaling the "fumes." After the coatings have cured for a few hours the potential hazard will have passed.
  • Provide adequate ventilation while you are doing the painting.