Surface family
Plastic and fiberglass panels: why Fe/NFe paint gauges can't read them
Magnetic and eddy-current gauges need metal under the paint. Paint on plastic bumpers and fiberglass is measured with an ultrasonic gauge.
Also listed as plastic and fiberglass, non-metallic substrates
Short answer
Magnetic (Fe) and eddy-current (NFe) paint gauges need metal under the paint, so they cannot measure paint on plastic bumpers or fiberglass. DeFelsko says coatings over plastic and fiberglass are measured with an ultrasonic gauge, which needs a couplant gel on the surface. A blank screen from an ordinary Fe/NFe gauge on these parts is expected.
What they share
- Gauge mode
- Neither Fe nor NFe: those modes need a metal substrate[3]UNI-T: the measured object must be metal with a non-conductive coating.
- What the reading includes
- Total coating thickness; some ultrasonic models also report individual layers[2]DeFelsko says its PosiTector 200 B3 can report total thickness and up to three layers. Layer reporting is model-specific.
- Published thickness figures
- Not confirmedNo source we checked gives a typical paint thickness on plastic or fiberglass parts.
- Polishing note
- Not confirmedNo source we checked gives polishing limits specific to painted plastic or fiberglass.
Watch out for
- A blank screen is expected. Fe and NFe modes need metal under the coating, so no reading on a bumper is not a finding about the paint.
- Ultrasonic gauges are specialists. DeFelsko says its affordable ultrasonic models are intended only for non-metal substrates and are not recommended as a do-all instrument.
- Couplant is part of the method. Ultrasonic measurement needs a couplant gel between probe and surface, per DeFelsko.
Paint and surfaces in this family
- Plastic bumpers and mirrors plastic bumpers, bumper covers, plastic parts
- Fiberglass panels fiberglass, GRP panels
Pick the part: plastic bumpers or fiberglass panels. We have no approved ultrasonic gauge to list yet.