How Do You Prevent the Faraday Cage Effect?

How Do You Prevent the Faraday Cage Effect?

Jun 20th 2019

The "Faraday Cage effect" happens when coating charged parts with sharp inside corners or recesses during an electrostatic coating process. The “effect” prevents powder from a gun from getting into those corners and recesses because they do not hold a charge. The difference in charge causes the charged powder particles above the corners and recesses to create resistance to incoming powder—the Faraday Cage—making it difficult to coat these areas.

While it might be impossible to prevent the Faraday Cage effect from occurring completely, there are ways to overcome it. Here are three "levels" of strategies and tips that will help you better coat inner corners, recesses, and many parts with odd geometries.

Level One – Overpower Faraday Cage effect:

  • Use slotted tip to concentrate the spray
  • Blast powder into recesses
  • Increase the powder flow rate
  • Maximize the gun to part distance

Level One Tradeoffs – These strategies can use excessive amounts of powder, have higher film thicknesses than desired, and could result in an uneven film build.

Level Two – Fine-tune the gun settings:

  • Use slotted tip to concentrate the spray
  • Decrease powder gun flow rates
  • Reduce gun voltage to 40-60 Kv
  • Maintain gun-to-part distance of 8-10 inches

Level Two Tradeoff – These gun settings could mean slower application times.

Level Three – Modify spray technique for unavoidable Faraday Cage:

  • “Finesse” the powder into corners and recesses
  • Spray corners and recesses of a part at obtuse angles
    1. Reduces air turbulence
    2. Allows for deeper penetration
    3. Minimizes early back ionization
    4. Utilizes more lines of force

For more information about how to fine-tune your application settings and techniques, read TCI Powder's Troubleshooting Guide, especially Chapter 10, “Powder Application Tips,” and Chapter 13, “Troubleshooting.”

…And more application tips…