Wet Film Thickness Gauge

Definition - What does Wet Film Thickness Gauge mean?

A wet film thickness gauge is a tool that is designed to measure a liquid coating's thickness in the easiest and fastest manner. It measures the thickness immediately after the coating has been applied on the material.

Wet film thickness gauges measure the thickness of almost all types of organic coatings such as:

  • Varnishes
  • Lacquers
  • Paints
  • Resins
  • Gel coats

It can also be used to measure powder coating thickness before it goes through curing. Wet film thickness is measured to determine the correct dry coating thickness.

Wet film thickness gauges are also known as wet film gauges, notched gauges, step gauges and Combs.

Corrosionpedia explains Wet Film Thickness Gauge

Wet film thickness gauges have notches or teeth that are machined into the gauge sides. The end points of the gauge serve as references to each other. For a particular side, the two notches carry the same size and act as the zero reference, which represents the substrate. The notches present on same sides are shorter relative to the outside notches. Each of these signifies varying distances from the outside edge teeth corresponding to zero. The distances represent the wet coating thickness surface that needs to be measured. The notches are marked off in MILS, which is equivalent to 0.001 inches.

A wet film thickness gauge must be placed at a 90-degree angle to the coated material and must be completely contacting it. Once the measuring gauge is taken out of the material, depth is determined by the MIL of the biggest notch that is wet by paint and the smallest notch that is not wet. For instance, if the largest notch that is wet is at 8 MILS and the smallest notch that is not wet is at 10 MILS, it can be said that the wet film thickness is at 8 to 10 MILS.

To achieve accurate measurements, the following must be observed:

  • Wet film thickness must be measured immediately after the coating has been applied.
  • The gauge must be used on a smooth, flat surface without irregularities.
  • Several measurements should be taken in series to get an average result.
  • The gauge should be cleaned with a soft cloth after use.

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