Common Reasons for Chipped Powder CoatingJune 11, 2019
Antiquated painted coatings chip easily, as you'd expect. Unexpectedly, powder coated parts should never chip. If that durable finish is exhibiting such obvious signs of sheathing breakdown, some unknown process variable has clearly gone awry. Hang tight, you're about to troubleshoot the common reasons for chipped powder coatings. Beginning with pretreatment mistakes, let's get underway, for there's more to follow.
A Pretreatment Failure
If the coating is chipped and the underlying material lays exposed, the elements now have access to a potentially corrosion prone substrate. A workshop owner might feel badly let down by his equipment at this point, but the problem has nothing to do with the curing oven or the powder coating booth. Rather, a gaffe has been made back in the pretreatment room. A layer of dirt or oil or corrosion has stubbornly stuck to the base metal. Because the powder fluidization cycle hasn't worked properly, the cured coating doesn't adhere to the underlying alloy surface. Left unattached like this, the finish detaches and chips.
Troubled By Undercuring and Overcuring Problems
If a corroded underlayer can interfere with the curing process, so can an improperly heated oven. This time around, the curing cycle hasn't finished because the oven temperature isn't hot enough. Alternatively, the oven temperature is set way too hot. The polished or colourfully hued finish discolours and darkens because of the excessive oven temperatures, then that overly baked coating chips and flakes away like a piece of eggshell on a badly boiled egg.
Powder Thickness Blunders
Expert powder coating shops configure and check their booth power supplies. Following this approach all the way to the electrostatic gun and the attached air compressor, the same expert approach adjusts the gun and air pressure settings until a focused cone of dry powder is emitted from the gun nozzle. Even the distance of that nozzle from the workpiece surface is carefully monitored. Thanks to these measures, the right amount of powder enshrouds a part's surfaces. That coating is neither too thin nor too thick. If it were too thickly applied, chipping problems could impact the finish.
In a way, powder coating technology is regarded as an art form. By way of example, a complex geometrical shape enters a sealed booth. The electrostatic circuit applies powder, but the Faraday Effect creates coverage-resistant areas in recessed corners. By applying more powder, the effect is overcome. Unfortunately, the finish is now too thick. It chips easily. As for the other issues, they're avoidable, but it might take some trial-and-error to get the oven and booth settings right. Regarding pretreatment gaffes, though, workpieces really should be properly cleaned up before they reach the coatings stage.
GP Industries Pty Ltd
1 Regal Court,
Vermont South VIC 3133
Phone: (03) 9802 1355
Fax: (03) 9802 6027
20 Burgess Road,
Bayswater North VIC 3153
Phone: (03) 9761 7676
Fax: (03) 9761 7671
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