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Question posted - October 23 to October 29, 2016:

What is the best way to assure compliance with specified dry film coating thickness requirements on vertical concrete?



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Selected Answers

From Tom Swan of M-TEST on October 31, 2016:
If you are looking for the same accuracy on a DFT gage for steel as for concrete, you are correct with your assessment. You will also get better accuracy on a thicker film coatings than a thin film coating because roughness of the substrate is less important. That being said, an electronic DFT gage will give reasonable accuracy in MOST scenarios. Take multiple readings and average them together and you should get a reasonably accurate number if you aren't looking of tenth of a mil accuracy. You can also use a Tooke or PIG to check the DFT. While it is destructive, the damage is limited to about a one- inch cut. These work best on thin mil coatings. Closely monitoring the coating application should always be the primary means of controlling thickness, but anyone that has been doing this for a while knows that does not always work. When it doesn't, an electronic DFT Gage can come in handy.

From ROY CANNON of Pecora Corporation on October 28, 2016:
One of the challenges in determining DFT on a porous and/or irregular surface such as concrete using traditional measuring devices, such as film thickness gauges, is the fact that the irregularities in the surface will skew results. Electronic devices also generally rely heavily on interaction with the coated substrate, also in which case both surface irregularity and composition may skew results. The most practical method of determining DFT on a vertical concrete surface would be to know the percent solids of the coating system utilized and closely monitor wet film coverage rates. This information is easily acquired from manufacturers, who are generally more than happy to discuss the particular surface to be coated. Consulting with a manufacturer's technical service team would be the best approach rather than relying strictly on literature or sales personnel.


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Tagged categories: Coating / Film thickness; Coating inspection; Dry Film Thickness (DFT)


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