Dry Film Thickness (DFT)

Definition - What does Dry Film Thickness (DFT) mean?

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. Proper thickness should be determined by recommended coating system parameters.

Corrosionpedia explains Dry Film Thickness (DFT)

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. It is critical that the applied thickness be sufficient to ensure corrosion protection as well as proper adhesion.

The maximum coating thickness recommended by a manufacturer is often based on a coating's resistance to sagging (sink). DFT is a parameter that is considered during quality control or inspection processes. Durability of a coating is function of DFT, whereas the thickness of an individual coating layer in a coating system and the total system DFT reported specifies the coating's durability.

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

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