# Dry Film thickness measurement questions



## BHGEPainter (Feb 28, 2018)

So I work in the oil and gas industry as an industrial painter we paint multiple different types, and sizes of products with peculiar geometries. The paint thickness required per specs is low some as low as 1.5 - 2 mils off paint. We are spraying aluminum based high temp paint on these valves. The steel we are painting is casted and rarely a smooth surface. We will read adequate thickness is a spot move slightly left right up or down and the guage will read double or triple the original reading! Can this be caused by the condition of the steel, or the fact we're using aluminum paint or the gauge not being on a flat surface? We are using a Delfesko Positector and it's causing me some serious head aches! Any information or advice would be much appreciated!!


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## PaPainter724 (Apr 22, 2016)

Could be some heavier spots that laid down into a divot because the metals not smooth. Also check your specs though because usually the film thickness is a minimum requirement not a max requirement and most architects/project managers/owners won't be upset if you're above their minimum. They do the thickness tests to make sure they're not getting robbed by someone trying to cheap out on paint.


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## CApainter (Jun 29, 2007)

BHGEPainter said:


> So I work in the oil and gas industry as an industrial painter we paint multiple different types, and sizes of products with peculiar geometries. The paint thickness required per specs is low some as low as 1.5 - 2 mils off paint. We are spraying aluminum based high temp paint on these valves. The steel we are painting is casted and rarely a smooth surface. We will read adequate thickness is a spot move slightly left right up or down and the guage will read double or triple the original reading! Can this be caused by the condition of the steel, or the fact we're using aluminum paint or the gauge not being on a flat surface? We are using a Delfesko Positector and it's causing me some serious head aches! Any information or advice would be much appreciated!!


I didn't see if that mil gauge you're using is magnetic, but I don't think the aluminum paint will affect it's operation because aluminum is not magnetic. A couple of things to consider:

1. Aluminum paint used for heat resistance should not exceed the recommended mils because they are designed to be a thin film.

2. With irregular surfaces, multiple readings should be performed in order to establish an average mil thickness.


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## jacob33 (Jun 2, 2009)

I have done some coatings for oil and gas industry and usually the blast profile has a surface spec as well. But usually the coatings company does the blast work so that probably doesn't help you. When we measured mil thickness we took multiple measurements and usually there was a min and max we were trying to be between so it was not like you have to hit 1.5 mill it would be dry film thickness between 1.5-4 mil or something like that.


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## painter213 (Nov 5, 2008)

What gage are you using, Type I or Type II? If Type I, then you should do a BM “ Base Metal” reading and this should be subtracted from each measurement taken. If it’s a Type II, then you should set up your gage with a plastic shim on the base metal to read from the highest peak. Since you say the surface is cast and it is rough, and your only applying a minimum amount, then this is the tricky part as you will still have surface roughness above to coating thickness. This is where as a estimator, that I’d figure in extra material, as I know that most likely, the painters will be exceeding the minimum thickness required for the job. Even with the use of a wet mill gage, due to the surface roughness, this makes it impossible to get a good reliable reading. There was a article done sometime back in JPCL the discussed coating on cast parts. Not sure of the date of the issue, but it was a good ways back. Good Luck! 


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