Measuring the Thickness of Dry Paint

Try Elektro-physik, Zorelco, or Defelsko.

Panametrics

What you're looking for is called a "coating thickness gauge"

http://tinyurl.com/ykwlo7u

There are relatively cheap units used by people who check out paint thickness on car bodies, after repairs have been made.

Someone once told me that some are simply a magnet on a spring with a pointer, the thicker the paint, the lower the attraction.....sounds a bit too primitive to me though....and of course they only work on steel!!!

Galal,

You do have a problem which is made more difficult due to the roughness and porosity of the concrete, but you might consider that the paint is an insulator and the concrete is not. If you know the dielectric constant of the paint, a typical alternating current capacitance meter and a form fitting conductive foil probe plate can be used to measure the coating thickness. If you do not know the dielectric constant, you can use a representative sample of dried uniform thickness paint applied to a polished flat of similar concrete for calibration purposes. If the concrete tank has some metallic support rings or reinforcements, these would complete the test measuring circuit. If no such thing exists, try wetting the exterior and apply a conductive foil, screen or similar wrap for the reference. The use of high frequency and high impedance will minimize the error that would be due to low conductivity of the concrete tank. You only need to know that the measured current will be inversely proportional to the coating thickness and directly proportional to the test plate area. I ruled out ultrasonic thickness measurement because of the assumed roughness of the concrete surface, but Kratcrammer-Branson many years ago made some very reliable portable instruments for just such measurements.

Good luck,

Luther M

You could paint a piece of sample concrete as a test coupon. After the paint is dry, you can cross section the cupon and measure the dry paint thickness with a microscope. These measurements are very accurate. For even higher accuracy you can cross section the cupon at an angle and correct your measurement using trig.

The following company Humboldt and their local rep may be helpful.

http://www.humboldtmfg.com/contact.php?page=contact/africa.php

I have seen some decent performance with a rebar finder configured for coating in the past, unfortunately age precludes details.

Hi Elden,

Sure you can measure dry film thickness. Only you need is the followings:

1) The number of gallon or litre you cover with the paint. Let say we used 100 imperial gallons.

2) Obtain the solids by volume of the coating from the manufacturer if is not your coating formulation. Let say the solids is 50%, just be easy.

From here, you can calculate the dry film thickness of your paint by the formula:

We know that 1 imp. gallon at 1 mil thickness covers 10x160= 1,600 ft2 as 100% solids by volume counted as water. One imp. gallon water weights 10 lbs and one gallon is 160 ounces. Your total surface covered with 1 mil of coating will be 1,600x100=160,000 ft2. If you cover with the 100 imp. gallons only 40,000 ft2. You have 160,000/40,000= 4 mils. Because the coating is only 50% solid (other 50% by volume is solvent or water), you obtain 4x50/100= 2 mils dry film thickness.

It's simple! For litres or any other units, make conversions and you get the answer, Gil.

Coating Thickness Gauge

Coating thickness gauge
Application of coating thickness gauge:used for measuring thickness and corrosion of pressure vessels, chemical equipment, boilers,oil storage tanks, etc. in industries of petroleum, shipbuilding, power station, and machine manufacturing.
F type coating thickness gauge can measure ferrous substrates.
N type coating thickness gauges can measure non-ferrous substrates.
NF type coating thickness gauge can measure both ferrous and Non-ferrous substrates.

Coating thickness meter Model: CM8821
Operating principle: magnetic induction (F)

Measuring range:0-1000um

Resolution; 0.1/1

Accuracy: 1-3%n or 2.5um

Min. measuring area: 6mm

Min. sample thickness: 0.3mm

Battery indicator: low battery indicator

Metric/ imperial: convertible

Power supply: 4x1.5V AA (UM-3) battery

Auto power off

Operating conditions:0-+45(32-104),90%RH

Dimensions: 160x68x32mm

weight: 250g(not including battery)

Optional accessories: other range 0-200um to 15000um

These are very simple to use and are very reliable we rarly fail these during precsion calibration. it's depending on the accuracy your looking