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 8082

White Stain/Contamination of Chemical Polished Al Extruded and Machined Parts



2001

Problem: White contamination/stain on chemical polished Al parts (6061).

The white contaminant was verified to be Aluminium Phosphate. Fallout is about 6-10%. Chemical Polish bath used @ 115°C:
Phosphoric acid: 70% (vol)
Nitric acid: 10 % (vol)
Acetic acid: 20 % (vol)

What could be the cause & remedy? Is there any simple selective titration method to determine the respective acid (nitric acid, phosphoric, acetic acid content) on the CP bath mixture?

What is the recommended bath composition by volume for CP process given the following raw chemical?

Nitric acid strength: 65%
Phosphoric acid strength: 70%
Acetic acid strength: 70%

Is acetic acid commonly used in CP process? If yes, what is the purpose?

Thanks

Tan Thong Guan
BJ Industries - Singapore


2001

Tan,

Try reducing your temperature slightly. Chemical polishing of Al is generally carried out at ~80 degrees C. It may be your chemical solution is too volatile at this increased temperature. Also, it could be as simple as inadequate rinsing. The rinse post polishing should be heated also. Fast changes in temperature are known to cause increased precipitation in chemical processes. Could explain the salt on the surface.

John Martyn
- Ireland

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