Measuring the dry film thickness of wood coatings is of great importance in quality control. The dry film thickness is negatively cor-related with the formation of coating defects like cracking and, thus, has a major influence on the service life of a wood coating (e.g. Grüll et al. 2014). In case of flame retardant (FR) paints and lacquers, the film thickness has a special significance as it is positively correlated with the reaction-to-fire performance (e.g. Mariappan 2017). CE marking implicates the control of the film thickness because FR-treated wooden construction products belong to AVCP system 1; this entails factory production control by a notified body according to EN 14915:2013+A1:2017+A2:2020. CE marking, however, does not cover the control of FR paints and lacquers applied by hand on construction sites. Therefore, portable instruments for measuring the film thickness accurately, fast and easy are of great value as they allow on-site inspections associated with internal or external quality control routines or liability cases. Of all film thickness measurement methods specified in EN ISO 2808:2019, the acoustic and the wedge cut method appear to be most appropriate. The present study compares the measurement accuracy and applicability between a portable ultrasonic and a wedge cut instrument with each other, considering the factors coating type, microfoam, the type of substrate and surface roughness.
Keywords: film thickness measurement, microfoam, quality control, wood coatings
Authors
Ulrich Hundhausen
NTI (Norwegian Institute of Wood Technology, P.O. box 113 Blindern, 0314 Oslo, Norway
Oskar Van Doorne
HOGENT, Minister Vanden Peereboomlaan 80 in, 8500 Kortrijk, Belgium
Login to download the PDF