Testing Clearcoats

Q. I am a chemist at a paint factory. We would like to do some testing for qualification of clear coats. What is the best way of testing clear coats over metal? What are some of the industry tests that can be used? Should it be tested by itself or with a basecoat? B. N.

 

A. It is always the best practice to test performance characteristics of coatings under their intended exposure conditions. Clearcoats for metal should be tested directly to the metal, without a base coat. You want to know if the clearcoat will protect the metal. Use of a basecoat will cloud the issue (no pun intended). If, on the other hand, the candidate clearcoat is part of a clearcoat/basecoat finish system, it must be tested over the basecoat.

In either case, meaningful tests to be run should include corrosion resistance (salt spray), humidity resistance, adhesion, impact resistance (direct and reverse). There may be other tests required to show performance characteristics required for specific markets. A list of these tests would be available from prospective customers supplying these markets.