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What is 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). 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
Why is it important to measure the dry film thickness of metal?
Film thickness significantly affects coating quality and costs. Measuring it, and knowing which gauge to use, should be routine for all coaters. Coating thickness plays an important role in product quality, process control and cost control, and it can be measured with many different instruments. Understanding the equipment that is available for film thickness measurement and how to use it is useful to every coating operation.
How do you measure dry film thickness on metals?
Magnetic induction paint meters use a permanent magnet as the source of the magnetic field. A Hall-effect generator or magneto-resistor is used to sense the magnetic flux density at a pole of the magnet. Electromagnetic induction paint meters use an alternating magnetic field. A soft, ferromagnetic rod wound with a coil of fine wire is used to produce a magnetic field. A second coil of wire is used to detect changes in magnetic flux.
These electronic paint meters measure the change in magnetic flux density at the surface of a magnetic probe as it nears a steel surface. The magnitude of the flux density at the probe surface is directly related to the distance from the steel substrate. By measuring flux density, the coating thickness can be determined.
What are the types of DeFelsko Dry Film Thickness on Metal products?
Eddy current techniques are used to nondestructively measure the thickness of nonconductive coatings on nonferrous metal substrates. A coil of fine wire conducting a high frequency alternating current (above 1 MHz) is used to set up an alternating magnetic field at the surface of the instrument's probe. When the coating thickness probe is brought near a conductive surface, the alternating magnetic field will set up eddy currents on the surface. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the eddy currents. The eddy currents create their own opposing electromagnetic field that can be sensed by the exciting coil or by a second, adjacent coil.
Do the DeFelsko Dry Film Thickness on Metal products require any formal training to use?
As for most equipment, the instruction manual is efficient. We do offer consulting, training, and troubleshooting services free of charge at MTest so give us a call and we can help you.