-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 10763

Passivating problems

adv.   stellar solutions banner


We are relatively new to the chemical business and are still going through our learning curve, our problem of the day is passivating 400 series stainless steel without the metal tarnishing or having a "rusty" look. Is diluting the acid a correct way to solve the problem or do we look somewhere else? We have done this in the past, had the same problem but we never know the size order we're getting and the separate mixture of acids isn't the best way for us to go we don't think. Any insight would be appreciated.


Derrell Fowler
- Cullman, AL, U.S.A.


Hello Derrell!

Likely the first thing you want to do here is read the FAQ that Ted and Tom have about passivation. Next, if you do a search of just on "passivation" you'll get a lot of letters, some of which bear on your problem. Finally, some of those letters were responded to by folks who work with citric acid passivation: I'd recommend you contact them, and they'll get you on track.

Good luck!

lee gearhart
Lee Gearhart



Per Lee's comments, there are excellent ways to passivate the 400 series stainless with citric acid without ruining the surface. There are citric acid formulations on the market that will work well. All citric formulations are not acceptable for this. DEFINITELY DO NOT dilute nitric acid to try this. It will make it worse. If you MUST use nitric acid, you will need to add sodium dichromate to the solution. See ASTM A967 [link by ed. to spec at TechStreet] .

lee kremer
kremer signature
Lee Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

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

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.