What Spraying Method Should You Use?

What Spraying Method Should You Use?

Jun 11th 2019

The best type of spraying application method for any particular Teflon™ coating depends upon a number of factors. That’s why we recommend you always consult Teflon Fact Sheets for both “preferred” and “not preferred” methods. Fact sheets outline Teflon properties and can even be as specific as what kind of gun to use, the best nozzle size, or what the ideal air pressure range should be, for instance.

Teflon coatings are usually applied with commercial spray techniques in a hood or well-ventilated area. You should keep water-based and solvent-based spray guns separate and not use one for both. Many coatings are shear sensitive, and the action of the needle moving in the fluid tip of the gun can cause coagulation. Minimize this coagulation by keeping the fluid delivery open and altering the fluid delivery by regulating the pressure on the pressure pot.

Manual Spray

More often than not, Teflon can be applied manually with compressed air and standard spray equipment. All spray equipment should be made from aluminum or stainless steel or coated with Teflon S. Transfer lines should be chemically inert and solvent resistant (e.g. Teflon tubing, polyethylene, or stainless steel). Air lines must be trapped to prevent oil or water from contaminating the compressed air or the product.

Manual Spray Application Tips:

  • Maintain a normal distance from the gun to the part of 4-12 inches (10-30 cm). If the gun is too close, the finish will look rippled. If it is too far, the spray will be dry and rough.
  • If you’re still getting ripples or rough finishes, reduce the atomizing pressure.
  • The spray guns should be held perpendicular to the piece using a flat, rectangular motion of the spray gun.
  • "Whipping" the gun in an arc tends to make the wet film bubble and will cause excessive beading on the edges of the part.

Automatic Spray

Automatic spray guns are generally used in large volume, conveyorized systems, where the parts to be coated are uniform in shape. While the set-up requires experience and careful adjustment, films can be applied more uniformly and at a faster rate. The finishes are fed to the guns through pressure pots with fluid pressures in the range of 5-8 psi (0.5-0.6 kg/cm2). Where flat items are carried on a flatbed conveyor, the spray guns may reciprocate transversely and spray continuously.

Electrostatic Spray

Electrostatic guns or discs are suitable for the application of many Teflon coatings. The advantages of electrostatic application include better film uniformity and 10% to 15% savings in material, due to the reduction in overspray. High volume production is usually required to justify the expense of automatic electrostatic systems, but relatively low-priced hand units are available.

Airless Spray

This technique uses high pressures to atomize and direct the coating material. Since the opening of the gun tip is generally smaller in diameter than in conventional compressed air spray, shear conditions during spray may be too high for aqueous Teflon products. Airless spray is generally used when coatings must be applied in deep recesses.

Powder Coating

Teflon powder coatings are free-flowing powders which are applied with conventional electrostatic powder equipment, with either spray guns or fluidized bed. The application voltage and technique depends on the particular equipment, although the highly attractive nature of the powder permits a wide range of application voltages.

What about Multiple Coats?

Many Teflon coatings can be applied in multiple coats. This process requires careful attention to bakes of intermediate coats to prevent deterioration of underlying coats. The opportunity to apply multiple coats also depends on the wettability of the intermediate coats. This property varies considerably depending on the product. Consult the Fact Sheet for the product you are using to see if it can be applied in multiple coats.

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Additional Resources:

Chemours-recommended “Guide for the Safe Handling of Fluoropolymer Resins”:
https://www.plasticseurope.org/en/resources/publications/108-guide-safe-handling-fluoropolymer-resins

Chemours introduction to Fluoropolymers:
https://www.chemours.com/Teflon/en_US/assets/downloads/pdf/teflon-introduction-fluropolymers.pdf

SPI Guide for Safe Handling of Fluoropolymers:
https://intechservices.com/content/SPI_Guide_for_Safe_Handling_of_Fluoropolymer_Resins.pdf

…And more application tips:
https://intechservices.com/teflon-application-overview