In powder coating as in life, we should aspire to be well grounded.
The good news is that, at least in the powder booth, proper grounding is easy to achieve. Please note that the following advice comes from someone whose powder coating experience revolves solely around metal parts.
Grounding starts with your infrastructure. Ideally, you want a metal rod extending 8-12’ into the dirt beneath the powder booth. That rod connects to a cable, which is hooked to a clamp, which attaches either to the part itself, or to the cart carrying the metal hooks on which your parts are hung – it doesn’t matter, as long as you’ve created a clean, continuous metal path from part to ground.
This metal-to-metal contact allows the charge coming from your powder gun to travel down the rod and disperse safely into the ground (hence the term “grounding”). Without an outlet, the charge has nowhere to go, leading to back ionization, poor transfer efficiency, and a whole host of other problems.
It all sounds very simple, and it is…until you realize that powder coating has an insulating effect on metal.
This means that hooks, crossbars, and hangers must be kept clean. These naturally have a tendency to collect powder coating over time; left unattended too long, that buildup will interfere with the metal-to-metal contact you’ve worked so hard to establish.
If you’re encountering grounding issues and aren’t sure whether it’s your hooks or your crossbar, it may be time to invest in a Megger. This handy little volt meter measures resistance. As you scan your hooks, carts, and cables, high resistance indicates a problem, letting you know it’s time to either clean or replace that part.
Powder coating is an electrostatic process. There’s plenty of room for difference of opinion on pretreatment and surface preparation, but good grounding is non-negotiable – without it, you simply won’t be able to build enough film thickness to protect the part. You may as well just buy some cheap spray paint from your local craft store.
It’s worth mentioning that a poorly grounded part will cause problems no matter what type of powder you’re spraying, but beware: you’re in for a special kind of nightmare if you’re spraying metallic powder coating. Whether it’s bonded or unbonded (but particularly if it’s unbonded), that metal flake will shed an unwelcome spotlight on every inconsistency, every charge concentration, and every instance of back ionization. Your transfer efficiency will be abysmal.
Keep an eye on your hooks and crossbars – always, but especially if you’re spraying metallic powder coating. You’ll be happier if you’re well grounded.