Metal Finishing Guide Book

2013

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CAN I ELIMINATE THE EPOXY PRIMER WHEN APPLYING CARC? Q: I am curious to know if it is always necessary to utilize an epoxy primer prior to applying [chemical agent resistant coatings] CARC? Would a substrate, such as fiberglass, be able to skip the primer and still meet the military specifications? A: I do believe it is possible to apply the CARC topcoat directly over fiberglass, especially if you apply sufficient film thickness > 1.8 mils to provide the necessary IR camouflage properties. However, I am not able to give you permission to omit the epoxy primer. For that you will need to get approval or a waiver from the weapons manager of the product you paint. You might even need to first obtain a letter from the Army Research Lab (ARL) advising that the omission of the epoxy is acceptable or necessary for adhesion of the polyurethane CARC to the fiberglass. Address your e-mail to Mr. John Escarsega, jescarse@arl.mil GROUNDING OPERATOR WHEN USING AN ELECTROSTATIC SPRAY GUN Q: What options are available for grounding the operator in a hand-held electrostatic spray gun system? A: The handle of all electrostatic hand-held spray guns should be grounded. Therefore, if your painter is experiencing electrostatic shocks, your first approach should be to test that the gun handle is grounded. The best option for a painter is to hold the handle firmly in the palm of his bare, sweaty hand and make good contact with the handle. By wearing gloves the painter isolates himself from the ground and will tend to build up an electrostatic charge. If he does wear a glove, he should cut a hole in the palm, so that he can have physical contact with the handle. Alternatively, one can purchase conductive gloves that are suitable for electrostatic paint application. Additionally, leather-soled shoes are better than rubber soles. I have also heard of painters wearing a grounded waist band, where the band or belt is in direct contact with the painter's skin. MEASURING DRY FILM THICKNESS ON VEHICLES Q: I am wondering if you can help me find the paint thickness specifications for a 2006 Pontiac G6. My car measures between 12–15 mils per panel. I measured two other panels, which ranged from 4–6 mils per panel. I think that, for some reason, the vehicle was painted twice in the factory. A: From the film thickness measurement you mentioned, I would agree with your assumption. A film thickness range of 4–6 mils is more realistic. I have never seen published data on the film thickness ranges for individual vehicles. Automotive assembly plants develop their own internal specifications for film thickness and might make this data available to their vendors, but I don't think the film thickness values are generally available to the public. If you are really diligent (and lucky), you might be able to find similar vehicles in public parking lots or at dealerships. If you get permission from the owner to measure film thickness, you're in luck. After measuring the film thickness on several identical vehicles, you will know for sure if your vehicle's panels were repainted. 559

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