Centrecoat WFT Wet Film Thickness Comb Gauge

This Wet Film Thickness Gauge is an important tool to measure the depth of paint and coatings applied to substrates to ensure the correct thicknesses are applied.

Best Uses

When applying paint or coatings to substrates, this tool should be embedded in the paint to measure the depth of the coating. This is extremely important when applying intumescent paint coatings, as their performance is dependant upon the correct thickness of paint being applied to the steelwork. This wet film thickness is calculated by the intumescent specialist at Promain. Some products will have predetermined WFT's that are published on the manufacturers' product data sheet.

What Is Film Thickness?

Film thickness refers to the thickness of an individual wet or dry film. Film thickness can also refer to the thickness of a paint system. Film thickness is presented as micrometres (μm) or millimetres (mm).

The corrosivity category, the paint type, and the desired durability time specify the film thickness of a paint system. In painting standards, paint system specifications and technical data sheets, the film thickness is indicated as the DFT - Dry Film Thickness. EN ISO 12944-5 (section 5.4) specifies the nominal dry film thickness. Wet Film Thickness is determined using a wet film thickness gauge. The thickness of dry film can be measured applying either a destructive or non-destructive method.

As the standards specify the inclusion of the surface profile in the dry film measurement in different ways, it is important to agree upon the applicable standard and specification. The film measurement methods are described in ISO 2808.

Instructions

Film thickness can be monitored during application using a wet film measurement gauge. Wet film measurement is carried out using a wet film comb immediately after application or before solvent evaporation of a coating. The measurement method is described in ISO 2808. The wet film thickness value (Km) can be read directly from the comb.

Press gauge into the wet coating. Withdraw the tool vertically and note the deepest tooth with paint on it and the next highest tooth that is not coated with paint. The true wet film thickness lies between these two readings. Clean the gauge with a suitable solvent after each use to ensure correct readings.

For WFT requirements, please refer to the individual paints and coatings data sheet prior to use.

How To Calculate Dry Film Thickness

Dry film thickness (K_k) can be calculated using the formula:
(1) K_k = K_m V/100 (μm)

V is the percentage of solids by volume. The percentage of solids content in the paint (V) is given in the technical data sheet, and the wet film thickness K_m is provided by the measurement.