Issue link: https://www.e-digitaleditions.com/i/1014893
POWDER COATING, August 2018 31 latinous (water-laden) conversion coating? It's typically recommended that the lm be air-dried for 24 hours or lightly cured for 60 minutes at a temperature less than 140°F. Finally, look closely into your rejects. Do they all fail at the same place or lo- cation on the part? Generally, if the failure is on the bottom, it's rinse- or contamination-related. Are the fail- ures all from the bottom, middle, or top of the racking location? If you could determine that, it would give me some clues to possible reasons for failure. Are failures sporadic during the process hours? Are they at the be- ginning, middle, or end of the shift? Can you have your paint manufac- turer or chemical supplier conduct analytical work on the back of the coating from failure? Optical micros- copy and scanning electron micros- copy with energy dispersive x-ray spectroscopy methods can really pro- vide clues to potential failure. I sincerely hope some of these ideas will lead you to problem resolution. If you have questions, please contact me. If you resolve the problem be- cause of anything written here, please let me know. PC Editor's note For further reading, see articles under the Surface preparation heading in the "Index to Articles and Authors 1990- 2017" Reference and Buyer's Resource Issue, Powder Coating, vol. 28, no. 6 (December 2017), or search the Article Archive at www.pcoating.com. All arti- cles listed in the archive are available for free download to registered users. they tend to ignore this simple miscue. Finally, three things stand out when reading the supplied information. First, you say that all chemicals are as hot as possible. You also state that the process is a batch tank line. I've seen many cases where parts will produce dry-down of chemical when hoisted from an active chemical tank to the subsequent rinse tank. Dry-down will complicate things and cause rejects. Check to make sure this isn't happen- ing on your line. Second, remember this, a part is no cleaner than the cleanliness of the last rinse. Have you ever checked your raw water for minerals, pH, conductivity, hardness? Poor water conditions create rejects when processing, especially when processing aluminum. Do you have reverse osmosis (RO) or deionized (DI) water for rinsing or nal rinsing? ird, I'm assuming your conversion coating contains chrome. If it's a chrome conversion, are you following the correct method for curing the ge- ACCELERATE YOUR CAREER AND YOUR BUSINESS AT FABTECH 2018 FABTECH 2018 ATLANTA NOV 6-8 Advance NORTH AMERICA'S LARGEST METAL FORMING, FABRICATING, WELDING AND FINISHING EVENT REGISTER TODAY FABTECHEXPO.COM #FABTECH18