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Reasons Why Powder Coating Can Bubble, Crack, and Peel Off

September 13, 2018

Like a bad case of skin rash, the powder coating is peeling off a workpiece. The exposed material underneath is going to corrode if the cause of the application defect isn't determined. Bringing the line to a halt, the equipment is on pause. The clock is ticking. What's making the normally unbreakable membrane crack? What's the root cause of the bubbling and peeling effect?

Outgassing Factors

Admittedly, the fault could be taking place at the pre-processing stage, where oily residues remain trapped. However, the trapped gasses that are producing the bubbling during the curing operation could also be a result of the metals' own underlying structural failings. The casting process, way back at the forgings factory, has heat-trapped the gasses. Galvanized parts are particularly susceptible to this effect.

Invisible Contaminants

To the human eye, the part to be powder treated looks immaculate. It's sparkling clean, smooth to the touch, and seemingly prepped for the powder coating booth. A short time later, although uniformly coated during the electrostatic phase, the cooling shell is cracking. In all likelihood, there's still a fine layer of foreign matter covering the metal. A comprehensively conducted cleaning and pretreatment service, one that perhaps includes phosphating, will resolve the issue.

Remedying Eggshell Peel Off

Substrate preparation could be hampering the application work, or there could also be a substrate compatibility problem in the offing here, so take the entire batch back to the powder coating enclosure, where the snag is likely occurring. Alternatively, this would be a good opportunity to reassess the process line's contamination control protocols. Is there water or dust getting into the equipment?

Arresting Large-Scale Peeling and Flaking Issues

A quality-assurance check mark has been issued against the pre-treatment room. The electrostatic equipment is also getting the all-clear, as is the pre-heating gear. By a process of elimination, we arrive at the curing oven. It's here that the over or under-curing powder is acting up and peeling in long sections. The flaking effect is clearly unacceptable, so what's the next move? Have that oven maintained and serviced, of course.

Fortunately, most of these processing problems can be picked up before the product batch leaves the workshop. If that's not the case, a dissatisfied customer is never good. Run test pieces through the line, have that equipment checked and rechecked, and turn the pre-processing room upside down if that's what it takes. Test pieces and troubleshooting periods may sound costly, at least initially, but these options are still far cheaper than a customer who has decided to take his business somewhere else.

GP Industries Pty Ltd

Head Office

1 Regal Court,
Vermont South VIC 3133

Phone: (03) 9802 1355

Fax: (03) 9802 6027

Email: gp_ind@bigpond.com


Factory G,
20 Burgess Road,
Bayswater North VIC 3153

Phone: (03) 9761 7676

Fax: (03) 9761 7671

Email: gpfactory@bigpond.com

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