-- The Home Page of the Finishing Industry

on this site
current topics

World's most popular finishing site / Internet's friendliest corner

topic 35084

Final Neutralization Rinse for Sulfuric Acid Anodize needed


A final acid neutralization rinse is needed for Mil-A-8625 [link is to free spec at Defense Logistics Agency,], TYPE II, CLASS 2 coatings before our final Deionized Hot Water Rinse and parts Drying process steps. I thought about a hot/warm sodium, or potassium, bicarbonate hot soak @ 1 oz/gal, but no experience on use or possible side effects of introducing a neutralizing bath. Reason being that aluminum parts have braze welds with tiny pores and crevices that have trapped acid. Unfortunately, we cannot use chromic acid anodizing. Maybe someone has used and controlled a similar neutralization solution.

Tom Andersen
Anodizing - Balto., Maryland, USA

Pickling of Stainless Steel
from Abe Books


1st of two simultaneous responses--April +++++

I'm not sure what you want to neutralize. If you're worried about sulfuric acid, they you should use dilute (5%) nitric acid after double rinsing after anodize. I know this sounds counterintuitaive, but it works. Alkaline materials should be avoided since they will 1) precipitate metals. and 2) may damage the anodize coating.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

2nd of two simultaneous responses-- 2005

Bicarbonate makes for a good controlled pH rinse as it is a buffer, so the pH tries to stay under 9.
That said, I doubt if you will get much neutralization of trapped acid in pores unless you add ultrasonics to it.
Also, Bicarbonate carry over into the seal or dye tank can significantly reduce the efficiency of that tank, which will require a lot more testing of those tanks.

James Watts
- Navarre, Florida

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

adv.: Anodizing Questions? Need Personalized Help?

anodizeusaConsult   probertbanner  

Disclaimer: It's not possible to 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 may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2019, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.