×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

corrosion of stainless steel through iron contact

corrosion of stainless steel through iron contact

corrosion of stainless steel through iron contact

(OP)
I am using iron tooling to bend stainless steel pipes, and even though i am using a metal foil for protection, on some spots the tooling is making friction contact with the stainless steel, there has been a lot of contact.

Will a nitric acid treatment repassivate the stainless steel, i.e, will the acid take care of areas where particles from iron tooling are deeply embedded in the stainless steel?

Will a 2500 psi water pressure wash be enough?

I'm trying to find the most reliable method to repassivate the stainless steel without having to sand all parts which had contact with the iron tooling.

        Thank you for any suggestions.

RE: corrosion of stainless steel through iron contact

Passivating with about 10% nitric acid (warmer is better)will remove the iron contamination. It also leaves a stronger passive film, modestly increasing the time before piting by chlorides occurs (compared to a non-passivated surface, even if it does not have iron to remove.)
2500 psi (or even 4000 psi) water blasting will not reliably remove iron contamination.
Rust stain from wetting the SS will reveal if the iron is still present.

RE: corrosion of stainless steel through iron contact

Dear Rustbuster1,
Thank you for your answer.
I am having some trouble to find a supplier for 10% nitric acid pickling or paste. Either companies provide a service to do passivation or chemical suppliers offer Nitric acid in liquid, undiluted form. I did find some suppliers in Europe and India but non in the States. (Im located in Brooklyn, NY)
Do I have to produce the pickling myself, and if how?
I would be very grateful for further suggestions.

RE: corrosion of stainless steel through iron contact

Roxy,

You could mix the solution yourself, using demineralized water.

If you are looking at localized areas, Copper supfate solution will identify the areas of contamination. the copper sulfate will turn any areas of contamination pink. These areas could be sanded with a flapper wheel and the test repeated until the contamination is removed.

Good luck!

RE: corrosion of stainless steel through iron contact

Though it's been some time, I seem to recall some companies beginning to use Citric based acids (claiming that they're more environmentally friendly). My apologies for lack of further information, but I might suggest that you contact the Nickel Institute who has been (in the past) a wealth of information on current stainless trends and technologies.

RE: corrosion of stainless steel through iron contact

Last I knew, one could buy "pickling" paste from AVESTA-SHeffield. This contains HF and HNO3 acids and therefore requires special care in handling.  They may also have a HNO3-only, passivating paste.  
As suggested, other acids besides HNO3 are also effective.  Phosphoric acid is a common alternative.  FYI- Coca Cola has enough phosphoric acid to give it a pH about 2.2 and has been used to remove rust from chromed bumpers on cars.  Warm the Coke to make it more aggressive ;<)

Checking with Nickel Development Institute (NiDI) will explain the technical aspects but is unlikely to locate a commercial source, but cannot hurt to try. They are at www.nidi.org

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close