Issue link: http://www.e-digitaleditions.com/i/799392
POWDER COATING, March 2017 25 The second choice is to mask the wheel and coat it assembled. This would require you to apply the first coat and only partially cure it for handling. Then you would remove the masking and remask the wheel covering that you just coated, expos- ing the new area. Now you will fully cure the wheel to ensure full coating properties. Be aware that the masking line where the two coats meet will be very sharp, requiring some final work (wet sanding and polishing) to blend the two areas. Good luck. —N.L. Keeping powder overspray out of places it doesn't belong Q I have a cylindrical part made of zinc (Z-3) that is powder coated. The part has a diameter that is about 2.25 inches at the base. It necks down to a diameter of about 1.25 inches. The height of the part is about 3.5 inches. The part is open from the bottom end. There is a female thread at the bottom end, which consistently gets overspray. The over- spray on the thread causes many prob- lems with assembly. The part is held in place on the coating racks by inserting the bottom threaded portion over an insert that is supposed to prevent the threads from getting coated. I've been given various explanations for the problem but no solution. One of the explanations is that a large amount of current is applied to the racks and that causes the coating par- ticles to draw into the threaded region. Another reason I've been given is that the spacing between the individual parts while mounted on a rack is not sufficient. On the surface, this seems like it's a process issue, but I'm not an expert in powder coating. Do these explanations sound reason- able? What additional information should I get acquainted with? R.D., San Antonio, Tex. A There is a little bit of truth in some of what you're being told. It's extremely difficult to seal off the threaded area of the part to prevent migration of powder into at least some of the threads. The fit of the plug will allow some migration. But, if you make the plug very tight, the coat- ing may flake when you remove it, or 1 t ? t i t P ™ Plaforization 1 minute? tank? step? eat in etr Pr BELIEVE IT! info@chemtecamerica com el: 954-228-1804 eston, FL 33326 T Tel: 954-228-1804 W 1535 N. Park Drive, Suite 104 Chemtec North America .chemtecnorthamerica.com www info@chemtecameric merica.com ca.com