Paint on Various Substrates

Most conventional coating thickness gages using eddy current or magnetic induction or other magnetic techniques can easily and accurately measure the thickness of paint on metals such as that on an automotive hood. They cannot measure paint on non-metal materials such as plastic bumpers, composites, wood or concrete.

This application note is about the non-destructive thickness measurements of paint on non-ferrous materials.

With the latest version of the Alphagage+ series in precision mode, the operator can easily recall from the standard probe library the default stored setup for Paint on plastic or paint on metal (see image 1). This measurement is done with a conventional 5 Mhz., .25” delay line. The thickness range of the paint is from .001” or 25.4 Microns to .100” or 254 microns. It is very important that the probe and part being tested are done in a stable temperature environment. It is important to know the substrate material so that the proper setup of the gage is chosen for the proper echo detection as a “phase reversal” will occur of the reflected signal with different substrates. In a paint on plastic scenario, the echo detection should be positive going as shown in image 2. While paint over metals should be set to detect a negative going signal.

Image 1: stored setup menu



Image 2: Paint on metal car hood.