How to measure powder coating film thickness.

Steps

1. Pick the right gauge

   On steel and other magnetic substrates, use a magnetic-induction gauge (ISO 2178 type methods). On aluminium and other non-ferrous metals, use an eddy-current gauge (ISO 2360 type methods). Many gauges combine both.

2. Calibrate on bare substrate

   Zero and check the gauge on an uncoated piece of the same metal and shape, using calibration foils near your target thickness.

3. Measure cured film

   Take readings on the cured, cooled coating. Readings on uncured powder are unreliable.

4. Take enough readings

   Measure several points per part, including edges, recesses and flat areas, and record the range as well as the average.

5. Compare with the target

   Check results against the film thickness on the TDS or your customer specification, and adjust gun settings if needed.

Parameters

Steel

Magnetic induction (ISO 2178 type)

Aluminium / non-ferrous

Eddy current (ISO 2360 type)

Target film thickness

per TDS / customer specification

Calibration

Bare substrate plus foils

Common mistakes

• Calibrating on a different metal or a flat plate when measuring curved parts.
• Measuring too close to edges where readings are distorted.
• Reporting only the average and missing thin spots.
• Comparing colour between panels coated at very different thicknesses.