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28 POWDER COATING, November 2016 • Stage two: City rinse • Stage three: A fluoride containing iron phosphate or a transition metal conversion (TMC) fluorozirconic conversion (stainless steel tank) • Stage four: City rinse • Stage five: RO-DI rinse The best process has always been hexa- valent chromium (Mil C 5541). There is a tri-chrome process developed by the US Air force/Navy that is replacing hex chromium and replacing Mil C 5541. It's a complex process and gets 500 hours to more than 1,500 hours of ASTM B-117. Most finishers don't or can't use chromium, so the best nonfer- rous process for high-technology coat- ings like PVDF, or Kynar, is as follows: • Stage one: Same as previous process • Stages two and three: City rinses • Stage four: Acid deoxidation • Stage five: City rinse • Stage six: RO rinse • Stage seven: Nonchrome conversion or nonchrome-containing seal rinse and TMC • Stage eight: RO-DI I suggest that you consider reading my article "Aluminum pretreatment: Old issues and new developments—part I and II." You can find it on www.pcoat- ing.com by clicking Article Index and then Authors. Scroll to G and find it under my name. It's a great article with the exception that it doesn't include the newest technology for TMC. Another one of my articles on TMC is listed under my name in the index. PC Editor's note For further reading, see articles under the Surface preparation heading in the "Index to Articles and Authors 1990- 2015" Reference and Buyer's Resource Issue, Powder Coating, vol. 26, no. 6 (December 2015), or click on the Article Index at www.pcoating.com. Articles can be bought online. Have a question? Click on Problem Solving to submit one. Show off your latest powder coating project. Highlight your newest equipment in operation. Shine a spotlight on your colorful collection of powder coatings. If you're curious about how you can get your company featured on the next cover, contact the editor at atyznik@cscpub.com Dare to be seen... on the cover of Powder Coating!