Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2003

Paint and Coating Dry Film Thickness

Q. What is the minimum finished dry mil thickness you recommend for an exterior paint used on ferrous metal (institutional use)? If I have two paint products, and one has a finished mil thickness of 1.4 and another 2.0, is this difference significant?

A. If you have two equivalent paints and a single coat of Paint #1 yields a DFT of 1.4 mils while Paint #2 yields 2.0 mils, the second is more likely to provide longer corrosion resistance. If Paint #1 incorporates corrosion inhibitors, while Paint #2 does not, then the reverse conclusion might be true.

When you compare two products for their performance you should also compare their solids content.