×
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

302 SS spring rusting?

302 SS spring rusting?

302 SS spring rusting?

(OP)
We have a 302 SS compression spring that rides inside a borosilicate glass (Pyrex) tube.  The wire dia is about .025 and the spring force is nominally 1 lb.

After about 250,000 cycles of the spring, it appears the spring is rusting on the OD where it rubs on the glass.  The environment is room temp, 4 psia air, in an "office-like" setting.  There are many rust colored particles nearby.

The spring was not passivated after coiling.

Any ideas on how this could be happening?  Could the rubbing remove the protective layer on the SS?

Nearby there is a steel part that is not protected from corrosion and there is no rust on that part.

Thanks,

Tom

RE: 302 SS spring rusting?

Sounds like the glass is rubbing thru the protective Cr oxide which is what makes stainless "stainless".  So why isn't the CS also rusting?  Because the 302 now has a large "relatively" cathodic area and a small rubbed anodic one.

Add the moisture in the air and a few conductive ions, and you have what you don't want-a miniature battery.

RE: 302 SS spring rusting?

If it is possible you can change the spring into a slightly tapered compression spring which will be more stable and will not rub on the glass wall.

RE: 302 SS spring rusting?

The rubbing may also be wearing very small particles off of the SS.  These have such a high surface area, and no passive film, that they will quickly rust.
You need to eliminate the rubbing contact.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm

RE: 302 SS spring rusting?

(OP)
Thanks for the quick reponses.

We already have a design change put in place where both ends of the spring are centered in one coil depth counterbores.  Previously it was centered on one end only, allowing the contact.

I posted so I could understand the mechanism behind the corrosion.  I'll need it to explain to our customer.

We're also just about ready to run a test comparing springs that rub and ones that don't.

Thanks again,

Tom

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