Static Spray

The write-up

Static electricity holds this paint in place. Charged powder clings to a grounded part until an oven melts it into a hard shell.

1. Exhibit A

   What the powder is

   Powder coatings combine polymer resins with curatives, pigments, leveling agents and flow modifiers. These are melt-mixed, cooled and ground into a uniform powder 'similar to baking flour'.

2. Exhibit B

   Charge and ground

   In electrostatic spray deposition the gun charges the powder and the part is grounded, so the electric field pulls particles onto it. The deposited powder keeps its charge, which holds it in place.

3. Exhibit C

   The oven does the rest

   The coating isn't finished until it's baked. In the curing oven the powder melts, flows over the part and cross-links into long molecular chains, usually at 325–450 °F (163–232 °C).

4. Exhibit D

   Grounding matters

   Powder build-up on hangers or conveyors degrades the path to ground. The total resistance to ground must stay under one megohm, which is checked with a megohmmeter.

5. Exhibit E

   Cleaner than solvent paint

   Powder is a dry process that eliminates solvents and virtually eliminates VOC emissions. Overspray can be collected and returned to the hopper for reuse.

6. Exhibit F

   Not just metal

   Electrostatic spray is mostly used on metal, but powder can also coat plastics and MDF, or be applied by fluidized bed (dipping a preheated part into fluidized powder).