Dry film thickness

Dear Readers,

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