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!
(one of the world's very few 'no registration' sites)

-----

White powder on anodized finish

August 12, 2021

Q. I am a machinist and we CNC machine parts. We received a batch of straight knurled knobs back from type 2 anodizing. In a few random places there is a white powder substance on top of the anodizing. The anodizing is perfect under the powder. The powder cleans off with a toothbrush.

61312-1

We run these same knobs with the same process all of the time without issue.

My anodizer says it is our fault because a burr on the knurl entrapped the seal coat. I contend that if a burr was the problem then there would have been other imperfections in the anodizing due to entrapment of other chemicals in the processes. It is simply a matter of the seal coat not being rinsed off properly.

What do you think?

Scott Dordick
- Pomona, California
^


September 2, 2021

A. `I am no machinist, but I don't think knurling is a very clean process. It results in folded edges and smeared material. These little void areas will wick in process solutions which are nearly impossible to rinse off. I would bet that you are seeing sulfuric acid electrolyte solution which is drying out and blooming sodium sulfate crystals

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.
supporting advertiser
Wadsworth, Ohio

luke banner
^


September 7, 2021

thumbs up sign Hi Chris,

Yes, knurling is formed by rolling dies on a spinning part so it is difficult to control the surface finish. We have been making this same part with the same process for 10 years and this is the first time we have had a problem. We have even used the exact same dies on another batch since the above parts and did not have a problem.

Scott Dordickre
- Pomona, California
^

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