Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2006

Measuring Dry Film Thickness (DFT) Over Abrasive Blasted Steel

Q: When measuring the DFT (50-75microns) of a primer applied over sand blasted steel with a surface profile of 50-75microns what effect does the profile have - would you expect the readings to be from 100 - 150mics?

A: Depending on the diameter of the film thickness measuring probe, you are probably only measuring the DFT above the peaks of the profile.  Therefore, 50-75 microns is probably the thickness of the primer over the peaks.  You can confirm this by spraying out a sample of the same primer on a piece of flat steel and comparing the film thickness over both substrates.

Best wishes,

Ron Joseph