Products Finishing

JUN 2014

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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PRODUCTS FINISHING — pfonline.com 33 PAINTING C L I N I C I will highlight a few areas that may be of help in finding a solution to your situation. As with any lami- nating process, your laminating bond is only as good as your weakest link. First, do you sand the parts in question? If so, are you adequately removing any sanding dust and debris? This may be an issue because, more than likely, the parts from China may be using gesso made with kaolin (china clay), which contains silicones found naturally in kaolinite. If this dust/debris is not removed adequately, it can create adhesion problems with the water-based paint. Second, gesso aside, you also mention what appears to be paint on the PUR glue bond, so I would like to propose a few simple tests you could conduct to validate the paint's adhesion properties. After you have sanded the gesso and successfully removed the dust/debris, simply spray a few pieces of the laminated/gesso substrate with the paint in question and allow it to dry completely. For Test 1, use a razor blade to make a series of lines in the dried, painted surface 1 / 16 -inch apart in both directions and approximately 1-inch square. Next, take a clear piece of 2-inch packing tape and place it over the top of this grid, rubbing it into place. Finally, grab a corner of the tape and quickly pull it off. Test 2 is similar to the first test, but apply the tape directly onto the surface without any razor cuts, and then pull it off as in the first test. Wagner Systems, I nc. 800.473.2524 www.WagnerKnowsLiquid.com Get clean, eficient and consistent liquid finishes even for your most unique applications with Wagner Mixing and Dosing Systems. TwinControl • Entry-level system for 2-K finishing and up • Password-protected control panel • High-performance Magnetic Stroke Meter and IceBreaker® Pump FlexControl plus • Modular control system for solvent or water-based coatings • Rapid color changes and easy integration of peripherals • Accurate mix monitoring and documenting with a 100 recipe memory FlexControl plus XL • High-volume fow rates and use of multiple guns • Many options to ft your personal requirements When it comes to liquid, Wagner has you covered. www.WagnerKnowsLiquid.com With either test, observe what is on the tape. Do you see little paint squares or gesso in Test 1, or whole sheets of paint in Test 2? If the gesso stayed in place on the laminate but the paint came off with either test method, this is a good sign that there may be a paint adhesion issue over this particular gesso formulation. Lastly, to further validate whether the paint could be the culprit, you can conduct a third test by applying the various laminates directly to the gesso surface without any paint. If the laminate bond is strong and there does not appear to be any issue with adhesion, maybe you could eliminate the paint step altogether, unless there is a specific reason it is needed. However, if a water-based paint is required, you may want to consider contacting your paint supplier and experimenting with other types of paints that would promote better adhesion to this particular gesso. The Painting Zone Have a question about painting? E-mail William or check out our vast library of painting articles at pfonline.com/zones/painting . 0614_PF_PaintingClinic.indd 33 5/16/2014 1:40:41 PM

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