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26 POWDER COATING, November 2016 face. Lexus black finish is kind of a stan- dard in some automotive specs. Some car companies tolerate a little orange peel since it can hide minor defects. The amount of dirt within a square foot area is another appearance spec. All of this should be dictated by your customer, however. If you don't demand a detailed spec on appearance from your customer, then you can have a real problem in the fu- ture. ASTM standards usually don't get into appearance issues because they de- pend on end use and vary from cus- tomer to customer. Get specs from your customer to avoid problems. —G.T. Cleaning powder from employees with compressed air We have powder coating booths, and I was wonder- ing what the regulations are to clean powder from employees in Michigan. Can you use air to blow off powder? N.H., Grand Rapids, Mich. I have no idea what the rules are in Michigan. However, the Federal OSHA (Occupa- tional Safety and Health Administra- tion) specifies that compressed air must be regulated, dispersed using safety noz- zles, or both to ensure that full line pres- sure cannot be used to clean operators. However, even with these precautions, there will be sufficient air pressure to re- move most powder from an operator's clothing. For the long-term wellbeing of your op- erators, you should look into using Tyvek suits (overalls) that are cheap and disposable. This will help you in two ways: It'll keep your operators' clothing clean, and it'll eliminate contaminants from their clothing (lint, dirt, etc.), which can adversely affect your process. —N.L. Avoiding contamination that can cause fisheyes We've been having a prob- lem with fisheyes. We pro- duce large toolboxes that on average weigh about 500 pounds. We have a seven-stage washer system and use phosphate coating. Our spray operation is manual. We bake the boxes at 420°F. From your experience, can you give me some information on some possible causes of fisheyes? Your help is much appreciated. T.N., Lakewood, N.Y. Fisheyes in paint got the name because that's exactly what they look like: fish eyes. The term originated in the liquid coat- ing industry. When a contaminant, al- most always a petroleum contaminant, is on the surface of a part that's to be coated, the contaminant will cause a de- fect that looks like a fish's eye. It will cause a void that goes to bare metal. It usually is from poorly cleaned parts that are contaminated by mill oils, preserva- tive oils, die lubricants, or overspray from a nearby operation. A glob of pe- troleum jelly in a paint pot does a mar- velous job of contaminating all of the paint lines. I've had that happen to me, and I hope the person who put the pe- troleum jelly in the paint pot has bad dreams. Powder systems can be contaminated and have fisheyes in the coating when the air compressor bypasses its lubricating oil, and it gets into the powder air feed lines. Fisheyes are not dimples in the coating. Dimples are caused from other problems. So, you should conduct a detailed search for contaminants on the part before it's coated. Are all of your parts affected? Steel warehouses are notorious for using preservatives that can be very difficult to remove. It won't hurt to verify that the compressor is delivering clean, dry, oil- free air to the system. —G.T. Curing powder coatings without heat Is there any such thing as a no-bake powder coating? If so, do you have any details on it? Thank you for your response. B.S., Taylor, Mich. All powder coatings require heat to melt and flow to form the coating on the part sur- face. Some specialty powder coatings can be melted and cured at very low temperatures (around 250°F). Others, referred to as ultraviolet-curable (UV- curable) powders, are melted with heat at 250°F and then cured by using a UV light source. Finally, there are powder coatings that can be applied by using a flame-spray gun that ignites liquid propane (LP) gas at the gun tip, which melts the powder as it's applied to the intended surface. All these methods in- volve heat to some degree, but offer al- ternatives to baking the powder coating onto the part. —N.L. PC Editor's note For further reading on the problems discussed in this column, see Powder Coating magazine's website at www.pcoating.com. Click on Article Index and search by subject category. Have a question? Click on Problem Solving to submit one. George R. Trigg is pres- ident of GRT Engineer- ing, Prospect, Ohio. He has been involved in the powder coating indus- try for more than 40 years. He holds a BSBA degree from Musk- ingum College, New Concord, Ohio. Nick Liberto is presi- dent of Powder Coat- ing Consultants (PCC), a division of Ninan, Inc., 1529 Lau- rel Ave., Bridgeport, CT 06604. Established in 1988, PCC is an independent engineering firm specializing in the use of powder coating technology. Nick has more than 3 decades of experi- ence in the powder coating industry and is a member of many industry associations, including the Application Equipment Technical Committee of the Powder Coat- ing Institute. A registered professional engineer in Connecticut, he holds a bache- lor's of science degree in mechanical engi- neering with a minor in physics. He can be contacted at 203/366-7244; email pcc@powdercoat.com; website www.pow dercc.com. Q Q A A Q A