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Long Term Storage of Conversion Coated Parts Prior to Painting, A Problem?

2007

We are storing a machined 6061 housing that has been conversion coated to MIL-C-5541 Class 3. The storage time is approx. 3-6 months is a well controlled (AC/Heat)stock room prior to applying a final prime and finish coat of epoxy primer and polyurethane paint.
We have had some chipping problems. My Questions
Is the Conversion Coating class 1A or 3 the correct coating for storage. I And, can the coating or the aluminum surface become contaminated and decrease paint adhesion. If so can you suggest a process to remove the contaminates to give better paint adhesion.

Kimber A. Rose
QA Engineer - Mason, Ohio

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I've heard (anecdotally) that cleaning with acetone ⇦this on eBay or Amazon [affil links] Warning! highly Flammable! helps.

Chemfilm becomes less hydrophilic (less wettable) as it ages. MacDermid advertises that Iridite NCP has better wettability for paints than traditional chem film, both initially and after aging.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007