Metal Finishing Guide Book


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face. When working for a military contractor, I always recommended that when DOD-P-15328 was applied to aluminum, painters were to dilute the wash primer with alcohol to reduce the acid concentration. Therefore, my recommendation is as follows: for aluminum surfaces apply MIL-P-8514C; for steel surfaces apply DOD-P-15328. I urge you to call the paint suppliers from whom you purchase the coatings and ask the chemist in the laboratory to provide a recommendation. CLARIFICATIONS ON SUITABILITY FOR POWDER COATINGS FOR MILITARY APPLICATIONS Q: We build communications equipment for the military. Most of this equipment is used in sheltered applications and, thus, is not exposed to the weather. We paint to meet MILDTL-14072 Finishes for Ground Based Electronic Equipment. We currently use one part alkyd enamel paints, and two parts epoxy paints. We are interested in adding powder coat paints, but this MIL Spec doesn't reference its use. I have found one MIL Spec on powder coat paint, MIL-PRF-24712. However, I'm unable to find a paper trail that will allow us to use this paint on our products. I've read that the military is interested in the use of powder coat paints, and that companies are using powder coat paint for military applications. However, it sounds like you have to get special permission to use it. Can you point me in the right direction? A: This is a very good and somewhat timely question. Powder coatings are one of (if not the best) coating technologies to protect a vast array of military products. They are tough, extremely durable, can be formulated in all colors and glosses, and are the most regulatory compliant of all industrial coating technologies. The specification you cite, MIL-PRF-24712 was originated in 1989 and revised in 1995. Surprisingly, there are no qualified products recognized by the military agency responsible for this specification. The specification covers a cornucopia of powder coating chemistries ranging from epoxy, to polyester, acrylic, and polyurethane. It also describes three different classes related to service environment (dry, immersion and immersion with weather exposure) and performance requirements. The military has recognized that MIL-PRF-24712A has become obsolete, and it is diligently working on a major revision. Part of this revision involves separating the immersion service classes from MIL-PRF-24712 and embodying it in MIL-PRF-23236. NAVSEA initiated this change to cover powder coatings used primarily as corrosion-control materials. The new version of MIL-PRF-24712 is expected to be published before the end of the year (2009). As for whether powder coating technology exists to meet MIL-PRF-24712 and MIL-PRF-23236, the answer is "yes." It is just a matter of an interested powder coating manufacturer submitting appropriate products to the governing military agency for qualification. I can provide contact information of individuals who may be willing to work with you in qualifying powder coating for these specifications. POWDER COATING MAGNESIUM ALLOYS Q: I have a cleaner/phosphate that is supposed to treat magnesium, but how should it be handled as far as dry-off and cure temps? I tried a couple of parts this morning, with a lowgloss clear coat and they came out looking like Desert Storm camouflage. This was cured for 12 minutes, at 360°. 562

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