Home /
T.O.C.
FAQs
 
Good
Books
Ref.
Libr.
Advertise
Here
Help
Wanted
Current
Q&A's
Search 🔍
the Site

Problem? Solution? Chime right in!
-- this is a no-registration site.

-----

"Chemical Film, Mil-C-5541, on Aluminum-Vacuum Systems"



2005

I recently used chromate conversion aluminum per Mil-C-5541 [link is to free spec at Defense Logistics Agency, dla.mil] on a vacuum system. When I disassembled the vacuum the chem film had changed appearance from dull to bright yellow. I have never seen chem film coatings change color under any circumstances-this is my first experience with it in a vacuum. Any ideas as to what is going on here? Can furnish a picture:

35985Thanks!

Bill Pinzon
aerospace systems - Greenlawn, New York
^


2005

Hi Bill,

On occasion we vacuum impregnate aluminium castings after they have been chem filmed, I can't say I have ever noticed any brightening of the conversion coating. However I have had some nickel-plated assemblies which exhibited some light tarnishing. After environmental testing at high vacuum these assemblies came out bright and shiny. You may be getting a similar effect, i.e., something is being removed from the surface during vacuum.

As an idea of the top of my head, follow a component through the conversion process and immediately after the final rinse lightly run your finger over the surface. Check to see if there is a thin film of smut. It may be this that is being removed giving the appearance of a brighter coating.

I have had similar experiences with castings were the chem film seemed to have taken fine to the metal but a thin film of smut was left on the surface making the coating look 'dirty'. I ultrasonic cleaned these parts and the chem film did indeed look brighter / cleaner.

If this is the case check your treatment line for contamination, old de oxidiser etc etc. It's also worth checking the component manufacturing processes, for instance the problem I encountered was due to contamination from a blasting process.

Richard Mosley
- North Yorkshire, UK
^

none
finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA