Powdercoating Failures: What Causes Air Bubbles, Cracks and Peeling?January 13, 2017
In following this guide, we're going to ring in the New Year with high-minded decorum by bending powder coating failures to our will. So, without further ado, it's time to make out a new resolution and find out just what causes air bubbles, cracks, and peeling in a newly coated product. Beginning with unsightly bubbles, let's put a decisive end to such aesthetic and function corrupting incidents.
Troubleshooting Air Bubbles
This condition suggests a preprocessing error, although several causes are possible. In starting with the preprocess station, porous surface defects can trap air and/or moisture in the component. The coating cycle will likely proceed without issue, but the oven will cause the gaseous contaminant to swell and burst through the powder. A pre-heat stage will eliminate the trapped air. Note, if the bubbling effect is occurring at a sharp bend, there may be micro-fractures in the metal. Again, preprocessing will correct the problem by paying particular attention to the site of the bend.
Detecting Cracking Causes
Under curing is the likely culprit, in this instance. The coating has properly adhered to the part, and there are no suspected pre-process problems, but the powder isn't cross-linking properly. Either the timing and temperatures are not being set according to the powder coating data sheet, or the oven's sensor isn't regulating the bake temperature according to its design specs. Again, part's stress or an invisible microfracture could be deforming the metal enough to cause a crack in the finish, but the coating's innate elasticity factor should accommodate this latter flaw.
Ending Peeling Headaches
This last production flaw turns a silk-sheened finish into an embarrassing mess. Instead of an impenetrable membrane with a super glossy aesthetic, the surface is marred by a flaking effect. The powder coating is peeling until the underlying metal or preprocessing layer becomes exposed. Take the process back to the beginning so that a definitive corrective action can be initiated. Logically, the first suspect would be the cleansing treatment. A greasy stain or a fine layer of oxidized metal does prevent powder from bonding properly.
Forgive the cheap pun, but this has been a short powder coating primer. As such, there are other possibilities that could cause the finish to bubble, crack or peel. For example, a high voltage charge will cause positive ions to form. This event alone will cause bubbles to form. Finally, always use the right powder coating products and the finest pre-treatment methods, for these represent the foundations upon which a professional service is built.
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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