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

World's #1 finishing resource since 1989
No login needed: Chime right in

topic 1677

Anodize Problem



1998

I have a problem that has surfaced on some Anodized parts I'd like your opinion on. The parts are made from Al. 7075 T 7351, they are chem filmed, masked and then Anodized type II. We've found that they have a "smutty" leopard pattern that appears to run with the material grain and does not rub off like something on top of the finish. We've been told, the problem is material surface crystallization that may be caused by contamination in the material, un-even heat introduced during the machining process or something introduced during the Anodizing process.

We've also been told the problem does not negatively impact the integrity of the part or the finish and is not a rejectable problem.

Additionally, we've been told that if we remove a small amount of surface material (approximately .005) that the problem will most likely be gone.

Do you have any thoughts or experience with anything like this ? What's your take on the advise we received ?

We plan to glass bead blast the surfaces, strip and re-Chem Film and Anodize. Does this sound like a viable re-work ?

Thanks,
Tom

Tom McGann
AZ76


1998

I have seen this caused by uneven cooling at the extrusion operation, when the parts are touching each other. Aparently silicon in the alloy migrates to the areas that remain hot longer, showing up as smut during chemical treatment.

Good luck,

Mike McDonald
mack products - Jefferson, Wisconsin

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