Over the past several decades,
industrial painting has changed, owing to the use of new, more durable
finishes. Coating is the most critical component in an anticorrosive coating
system. The main function of coating is to provide corrosion protection by
adhesion to the substrate. A coating thickness gauge (also referred to as a
paint meter) is used to measure dry film thickness.
Dry film thickness (DFT) is the
thickness of a coating as measured above the substrate. This can consist of a
single layer or multiple layers. DFT is measured for cured coatings (after the
coating dries). Thickness of a coating depends on the application and type of
process employed. DFT is
a parameter that is considered during quality control or inspection processes.
Dry film thickness (DFT) can be
measured using two methods: destructive thickness measurement, where the
coating is cut to the substrate using a cutter; and non-destructive coating
thickness measurement, using techniques which do not damage the coating
Dry film thickness can be measured on
either magnetic steel surfaces or non-magnetic metal surfaces such as stainless
steel or aluminium using a digital coating thickness gauge. The principle of
electromagnetic induction is used for non-magnetic coatings on magnetic
substrates such as steel. The eddy current principle is used for non-conductive
coatings on non-ferrous metals substrates.
Types of DFT gauges include:
Magnetic pull-off (Type I)
Constant pressure probe
(Type II)
Electronic magnetic flux
Eddy current gauge
Standards concerning DFT measurements
include:
ISO 2808
BS 3900 Part C5
BS 5494
ASTM D1005
D1400
D2691
SIS 184160
