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Powder Coating: The Importance of Contamination Control and Humidification

April 15, 2016

As the powder coating industry sails forward, it's buoyed by an untainted reputation, one that promotes a shell-like finish. The process adds durability to products, weatherproofs them and wraps these pleasing benefits in an attractive finish that can assume any colour or texture. Still, as with any technologically superior process, there are caveats, issues that can compromise a less-than-optimal workspace. The dry finishing process uses electrostatic technology to distribute pigment-loaded powder before sending the newly coated part into an oven for curing. But beware, for the bridging medium in this high-end process is air, and atmospheric mediums can introduce unwanted effects.

Incorporating Contamination Management Strategies

Pretreatment work removes corrosion and dirt from the surface of the part to be treated, and the surface is prepared to accept the powder coating stage. Electrodes are attached, powder guns are lifted, and the job commences. Unfortunately, there's an unknown quantity circulating around the heads of the coating technicians. The air is potentially full of particulate matter, the bits of metal and wood from other parts of the workshop, strands of hair, and loosened dirt that just spontaneously decided to eject itself from a cooling duct. Contamination management removes these airborne threats and stops the part from blemishing. These contaminants undermine the aesthetic appeal of the part and compromise mechanical-enhancing features, thus weakening the finish. In combating this issue, room filters and powder recycling sieves remove particulate waste. Better yet, a sealed cubicle or cleanroom eliminates such problems and places finite environmental control in the hands of the operator.

The Essential Nature of Humidity Control

Every time a brochure on powder coating is compiled, the word "dry" receives extra mentions throughout the publication. Powders need dry air to maximize distribution and dismiss unpredictable ambient effects. Fluctuating damp can cause all sorts of nasty headaches, including pigment clumping and poorly dispersed material coverage. The unevenly coated parts are no longer defined by a smoothly applied veneer of dry powder, which means the coating will split or form into tiny balls. Remember, this is an electrostatic technique, so a finite amount of moisture is desirable in order to enable ionization to take place, but the humidity must be controlled if the hygroscopic powder is to coat a surface evenly.

After pretreatment and electrostatic configuration work is conducted, adjust relative humidity and keep it around the 50 - 60 percent mark. As for contaminated powder, incorporate an air cleansing system with filters and use sieves to recycle waste powder.

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

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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