×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Recommended passivation method for 303 SS

Recommended passivation method for 303 SS

Recommended passivation method for 303 SS

(OP)
What would be the best method to passivate 303 Stainless Steel?

In order to get a good clean on the material, it is placed in

1) electro chem (with current) to remove oil
2) phosphoric acid
3) passivate solution

however, the phosphoric acid will react with 303 leaveing a stain on 303; without phosphoric acid, part will have sign of rust in salt chamber.



RE: Recommended passivation method for 303 SS

dchu129,

The phosphoric acid is there to act as a chemical polishing or etching solution depending on whether you get good leveling or not. It's used to remove material indiscriminately to prove a 'fresh' surface for the passivation solution to act on. Try adding an oxidizer such as nitric acid or H2O2 to help 'drive' your reaction so that all oxide films are unstable. Be careful H2O2 needs to be kept at room temperature or it will break down and create a dangerous mess!

metalhead

RE: Recommended passivation method for 303 SS

Carpenter recommends 20% HNO3 with 22g/l of sodium dichromate addition. Time is 20-30 minutes.

RE: Recommended passivation method for 303 SS

swall,

I think the question pertains to the chemical material removal step using perchloric acid, but I could be wrong.

metalhead

RE: Recommended passivation method for 303 SS

Are you doing the initial cleaning in an alkaline?
you then rinse well?
I would seriously look at using nitric acid for passivation.
20-25% just warm, not hot. (100-120F)
DI water rinse after.

You may always get some staining from the attack of the inclusions in the 303.  The help machining but reduce corrosion resistance and mar the appearance.  

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources