What Does DFT Mean? Understanding Dry Film Thickness in Protective Coatings

When it comes to protective coatings, DFT, or Dry Film Thickness, is one of the most important measurements to get right. Whether you’re coating steel, concrete, or any other substrate, achieving the correct DFT ensures the coating system performs as intended — providing long-term protection against corrosion, wear, and environmental exposure.

At Industrial Coatings, we help customers understand and achieve the right DFT for every project, from industrial steelwork and marine structures to building maintenance and flooring systems.

What Is Dry Film Thickness (DFT)?

Dry Film Thickness refers to the thickness of a coating layer once it has fully dried or cured. It’s typically measured in microns (µm) and determines how much material remains on the surface after the solvent or water has evaporated.

Getting the correct DFT is crucial for ensuring a coating’s performance, durability, and compliance with international standards such as ISO 12944, NORSOK, and manufacturer specifications.

Why Is DFT Important?

Applying a coating too thin or too thick can lead to costly problems down the line.

• Too thin: The surface may not be adequately protected against corrosion, chemicals, or abrasion.

• Too thick: The coating could crack, blister, or fail to cure properly — all of which reduce lifespan and protection.

By applying the correct DFT, you guarantee the coating system performs as designed, providing maximum protection and cost-effective longevity.

How Is DFT Measured?

Measuring DFT accurately requires specialist equipment. Common tools include:

• Magnetic gauges – Used for non-destructive testing on ferrous substrates such as steel.

• Eddy current gauges – Suitable for non-ferrous metals like aluminium.

• Ultrasonic gauges – Used for coatings on non-metallic substrates such as concrete, plastic, or wood.

Professionals often perform multiple readings across the surface to calculate an average DFT, ensuring consistency and compliance with the project specification.

DFT and Coating Specifications

Every coating product has a recommended DFT range provided by the manufacturer. For example, a zinc-rich primer might specify a DFT of 50–75 µm, while a high-build epoxy could require 200–400 µm.

At Industrial Coatings, our team works closely with clients to help them select coating systems that meet their performance requirements — and to ensure the correct film thickness is achieved for optimal protection.

Wet Film Thickness vs. Dry Film Thickness

Before a coating dries, it’s often measured as Wet Film Thickness (WFT). As the coating cures, the solvents or water evaporate, reducing its thickness to the final DFT.

To calculate the expected DFT from WFT, applicators use the formula:

DFT = WFT × Volume Solids (%) / 100

Understanding this relationship helps applicators apply coatings correctly the first time, reducing waste and rework.

Achieving the Correct DFT with Industrial Coatings Ltd.

With decades of experience supplying industrial and protective coatings across the UK, Industrial Coatings provides full technical support to help you meet project specifications. Whether you’re working on steel structures, storage tanks, or concrete flooring, our experts can guide you on the correct coating systems, DFT targets, and application methods.

Contact Our Team

If you need assistance with DFT calculations or coating system selection, contact our technical team today.