Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

August, 2008

Painting Enamel Over CARC

Q: What happens if you spray an enamel top coat over a CARC top coat? The CARC was sprayed and in less than 24 hours the enamel was sprayed over the CARP. What problems could we expect?

A: It is not a foregone conclusion that you will have any problem, since it depends on the resin of the topcoat. If the solvents in the polyurethane CARC are compatible with the enamel resin, or visa versa, you might not experience any problems. On the other hand, if the solvents are incompatible you might get lifting or blistering. In some cases, the strong solvents of the CARC could act as a paint remover to the enamel. Further, if you did not allow sufficient time for the solvents in the CARC to evaporate you might observe blistering and lifting of the enamel.

Have you experienced any problems? If so, what are they.

If you conduct an adhesion test per ASTM D3359 Method A or B, you will quickly determine if a problem exists. If the adhesion is good (measured as a 4B or 5B), you will probably not experience and problem.


Ron Joseph

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