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Again with the Test Panels? Process of elimination or eliminate the process?

November 26, 2010

Long time reader, first time poster.
Background: I am in the coating industry, Aero\Mil specialization.
Process's in question:
MIL-DTL-5541 type-I: clean(turco 4215NC-LT), Double rinse(two tanks), Deox(chem-alum deox 560),double rinse, conversion coat(Alodine 1200S), double rinse. processing for over 12 years
MIL-DTL-5541 Type-II:clean(turco 4215NC-LT), Double rinse(two tanks), Deox(chem-alum deox 560),double rinse, conversion coat(Alodine 5900), double rinse. tank set-up 3 weeks ago.

This has been a bad year for test panels in our shop, 3 failure instances:
1 on 2024 class 1A: in April, 2 panels more than 5 pits 3 panels no pits.(no pits on 6061) cause-suspect panels(in shop for 6 months)(first time I visited Finishing.com) Action taken procured new panels,(purchasing limited to 3 month supply for test panel procurement based on every article I have read regarding test panel failure)problem solved all panels pass.

second failure July, 2024 approx. 20 pits accumulated on 5 test panels(second failure in a year-start pulling my hair out!)(3 pits on 2 panels 6061? concerned) send out samples for solution analysis elevated chlorides, elevated copper still in operating parameters. Rebuild tank. Problem solved.

October build Alodine 5900 tank(same line as 1200S separate final rinse, share soap and deox tanks.
last failure Nov: 5541 type-I on 2024 class 1A and 6061 class 3 excessive pits accumulative. 5541 Type-II all pass, no pits

Finally My Questions:
Would passing the type-II panels eliminate the soap and deox as suspects from my new investigation?
Could a chem film tank spoil that fast? Titrations look excellent: concentration is 1.9, temp is steady at 85 degrees F, PH is 1.65(I am running out of money -multiple test panel groups sent to multiple testing facilities- and I just noticed a bald spot-running out of hair)
we do not process that much chem-film work. we are primarily a Paint Shop. we conversion coat to bring in more paint work......Oh ya and were....NADCAP'd
I believe if I run another set of panels without changing a thing they will pass!

Thank you for letting me Vent,
Balding in the Southwest.

John Spade
coating facility - Phoenix Arizona

We gave our test panels a quick sanding with an orbital sander and fine paper. I then rinsed them off in DI water, blew them dry and inspected both sides of the panel in good light. I rejected any panel that had a visible pit, regardless of how small. We did not have any failures until we got a bad lot of chem film from a MAJOR vendor. They finally admitted that their retained QC sample was bad, but could not supply us with another lot #, so we switched to another brand.

James Watts
- Navarre, Florida
December 1, 2010