Wet film thickness plays an important role in the inspection of coatings and coatings, as the uniformity and good coating of coating films is one of the key factors to ensure coating performance. Wet film thickness measurement is one of the key steps to ensure coating quality. In the process of wet coating preparation, the measurement of the uniformity and thickness of the wet film is crucial to the final performance of the coating. This paper will introduce the measuring tools and applicable methods of wet film thickness, including wheel gauge and comb gauge.

Wheel gauge
Scope and description

Wheel gauge is a tool for measuring wet film thickness on laboratory test plates or newly painted surfaces. It measures the wet film thickness by gently rolling on the wet film surface to ensure the uniformity and quality of the coating.

Wet film thickness measurement tools and applicable methods

Instruments and materials

The wheel gauge is composed of three coaxial wheels, of which the middle wheel is slightly smaller and eccentric, with a height difference. When the wheel gauge rolls over the wet film surface, the edge of the middle wheel will touch the wet film surface, thus reading the wet film thickness.

Determination method

When testing, the wheel gauge should be placed vertically on the wet film surface to ensure that the maximum scale of the two outer wheels is in contact with the substrate.

The wheel gauge should roll 180° on the wet film without swaying from side to side. Then, observe and mark where the middle wheel edge first touches the wet film surface.

Read the thickness of the wet film according to the scale on the wheel gauge. To obtain representative results, multiple measurements can be taken at different locations.

Result representation

The thickness of the wet film is expressed in micrometers (μm) and is measured several times at different locations to obtain representative results.

Wet film thickness measurement tools and applicable methods

Reference standard

In the measurement of wet film thickness, you can refer to the national standard GB/T 13452.2 “Color paint and varnish film thickness determination”.

Wet film thickness measurement tools and applicable methods

Comb gauge
Scope and description

Comb gauge is a tool for measuring wet film thickness in field painting operations. It can provide a rough estimate of wet film thickness and is suitable for paint construction sites.

Instruments and materials

The comb gauge is made of metal or plastic sheet and has comb teeth. The outer teeth at both ends of the comb gauge are in the same horizontal plane to form a baseline, while the inner teeth in the middle have different gaps from the horizontal plane, corresponding to different wet film thickness values.

Determination method

When measuring, the comb gauge is pressed vertically and firmly against the wet film surface so that part of the teeth are wet with the paint.

After removing the comb gauge, check and determine the position of the shortest tooth that makes first contact with the wet film surface and compare it to the position of the tooth that is not wet with the paint.

The wet film thickness is recorded based on the reading between the last wet tooth and the tooth that is not wet.

Wet film thickness measurement tools and applicable methods

Result representation

The thickness of the wet film is expressed in micrometers (μm) and is measured several times at different locations to obtain representative results.

Reference standard

In the measurement of wet film thickness, you can refer to the national standard GB/T 13452.2 “Color paint and varnish film thickness determination”.

Wet film thickness measurement tools and applicable methods are shown in Figure 2

Accurate measurement of the wet film is essential to ensure the performance and quality of the paint. By using appropriate measuring tools and methods, the thickness of the wet film can be effectively controlled, thus ensuring the performance and quality of the coating in different applications. Wheel and comb gauges are common tools for wet film thickness measurement, and they can play a key role in paint construction and quality control.