Nothing ruins a powder coater’s day faster – or more thoroughly – than rework.
Rework pops up in the oddest places, at the most inconvenient times. Experienced powder coaters are not immune. While we cannot escape the laws of entropy, we can be proactive about avoiding some of the more common rework traps (provided we know what they are).
Here are five common rework traps, and how to avoid them.
Grease, Oil, and Dirt
These are the most obvious culprits. Whether they arrived on the part or were transferred there (i.e., via greasy hands, improperly-filtered compressed air, or ambient dust floating around the shop), these three things need to be dealt with before the part is coated. Keep everything as clean as you possibly can – the parts, the shop, your equipment, etc., and never touch metal with bare hands.
Pretreating the part is half the battle. It also needs to be dried, paying special attention to enclosed spaces in which water could be trapped. Standing water will ruin your coating in one of two ways: 1. By bubbling up in the oven and running across coating as it cures; or 2. By preventing the substrate from getting to temperature, resulting in under-cured areas.
This is an obvious one, so I won’t belabor it. Be consistent with your spray patterns, stay cautious with your gun-to-part distance, and check your work with a flashlight before and after it cures.
Assume that anything you spray, dispense, or apply anywhere on the shop floor will somehow make its way back to the part. Cleaning products, aerosols, lotions, colognes, hand sanitizer – if it’s in the shop’s air (or on the operator’s body), it poses a threat. Keep mists, scents, gels, and aerosols off the shop floor as much as you can.
Silicone is a curse word in the powder shop. As the powder coater, you can’t control what lubricants the manufacturers are applying to their parts, but it is your job to remove them before coating. If you’re using silicone masking plugs, consider waiting until after pretreatment so that the chemicals don’t cause silicone to leach all over the substrate. Remove any silicone jewelry (wristbands, rings, etc) before approaching parts.
The only thing worse than rework is rework that could have easily been avoided. Stay vigilant.