FILM THICKNESS -

Film thickness measurement plays an essential part in the use and testing of paints and coating materials. The film thickness is a decisive factor in determining appearance, protective qualities and durability. Film thickness in coatings can have a big impact on cost and quality. Measurement of film thickness should be a routine event for all coaters.

A film, which is too thin, will afford inadequate protection and reduced hiding power. For this reason, technical specifications stipulate minimum film thickness and regular controls must be carried out to ensure that these values are consistent.

On the other hand, an excessively thick film is the result of using too much coating material, causing costs to increase accordingly. Furthermore, thicker coatings do not always mean an improvement in properties- for example; they have an adverse affect on drying time.

The physical and mechanical properties of a coating are directly dependent on the film thickness. If meaningful testing is to be conducted, the film thickness must therefore be uniform.

The correct gauge to use depends on the thickness range of the coating, the shape and type of substrate, the cost of the gauge, and how critical it is to get an accurate measurement.

WET FILM THICKNESS -

Wet film thickness is the thickness of a wet paint or liquid coating film immediately after application, before it begins to dry. The wet thickness is greatest immediately after coating application and becomes less as solvents and other volatiles evaporate from the film.

It is important that a coating is applied to the correct thickness. Applying too much wet coating will not only waste time and money, but there is also a possibility of the coating cracking during the curing process. Too little coating and there is a chance that the substrate will not be sufficiently covered.

Measuring wet film thickness during application identifies the need for immediate correction and adjustment by the applicator. Correction of the film after it has dried or chemically cured requires costly extra labor time, may lead to contamination of the film, and may introduce problems of adhesion and integrity of the coating system.

To control process variables, it is often desirable to measure whilst the film is still wet. The wet film conformal coating thickness method ensures quality control while the coating is still wet.

Wet film measurements are also useful for systems where the dry film thickness can only be measured destructively.

Wet film thickness gauges are used to check freshly applied coatings and can also be used to calculate the resulting dry film thickness. If deviations from the specified value are detected, corrective measures can be taken immediately. Wet-film thickness gauges help determine how much material to apply wet to achieve a specified dry-film thickness provided that the percent of solids by volume is known. They measure all types of wet organic coatings, such as paint, varnish, and lacquer on flat or curved smooth surfaces.

The wet film gauges are applied to the wet conformal coating and the teeth indicate the thickness of the conformal coating. The dry film thickness can then be calculated from the measurement.