Dry film thickness (DFT) also know as coating thickness gauge 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). Dry Film Thickness is probably the most critical measurement in the coatings industry. It provides vital information as to the expected life of the substrate, the product’s fitness for purpose, its appearance and ensures compliance with a host of International Standards.The thickness of a coating depends on the application and type of process employed. Proper thickness should be determined by recommended coating system parameters.
A coating is the most critical component in an anticorrosive coating system. The main function of a coating is to provide corrosion protection by adhesion to the substrate. It is critical that the applied thickness be sufficient to ensure corrosion protection as well as proper adhesion.
Film thickness is measured to ensure its compliance with ASTM, ISO and other specifications. There are coating inspection tools that are used at every stage of the coating process to ensure DFT meets correct specifications.
Types of DFT gauges include:
- Magnetic pull-off (Type I)
- Constant pressure probe (Type II)
- Electronic magnetic flux
- Eddy current gauge
The standards concerning DFT measurements include:
- ISO 2808
- BS 3900 Part C5
- BS 5494
- ASTM D1005
- D1400
- D2691
- SIS 184160
