No registration or passwords; no pop-up ads -- just aloha, fun, & answers.
(as an eBay Partner & Amazon Affiliate earns from qualifying purchases).
Home /
T.O.C.
Fun
FAQs
Good
Books
Ref.
Libr.
Advertise
 
Help
Wanted
Current
Q&A's
Site 🔍
Search
pub  Where the
world gathers for metal finishing
Q&As since 1989



-----

Rust on 303 ss after passivation





Hi, my name is Jill and I am a Quality manager. We are seeing parts come back from the passivation process that are showing signs of rust within a day or two after passivation. What could be causing this?

Jill Dechert
Quality Manager - Reading, Pennsylvania, USA
August 31, 2011



Steel or iron embedded in the surface is the normal cause. Passivation will only remove a portion of it.
If you want a problem that can never be solved, use a 410 rotary brush on a quality SS. It will look like it has the measles in a few hours of salt spray. Yes, even on high nickel and 316LSS.

James Watts
- Navarre, Florida
First of two simultaneous responses -- September 2, 2011



Jill,
Could you please share with us what passivation process you are using, including parameters such as immersion time, bath temperature, acid concentration, and any pretreatments you are doing?

Also be aware that 303 is a high sulfur grade (to improve machinability) and oftentimes the appearance of rust on the surface of parts is not iron oxide at all but actually sulfur bleeding out.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner
Second of two simultaneous responses -- September 2, 2011



September 7, 2011

Hi Ray, appreciate the feedback. Here is the process used by our outside passivator.
Cleaning Process:
Alkaline electroclean - Trimax279, 1-3 %volume 279, 3-9% by volume LC-B, 160-180 degrees F. 20-40 amps per square foot, 3-5 minute immersion.
RINSE - Ambient temperature, 1- 2 gallons per minute, 20 second - 1 minute immersion.
HYDROCHLORIC ACID - 40%, ambient temperature, 30 seconds -3 minute immersion time.
RINSE - Ambient temperature, 20 second - 1 minute immersion time.
RINSE - Ambient temperature, 20 second - 1 minute immersion time.
Passivate:
TYPE II & VI -20 -45% Nitric acid, 70-90 degrees F, 30 - 50 minute immersion

Jill Dechert
- Reading, Pennsylvania



September 29, 2011

Jill,
Alkaline pretreatment is good.

The grade vs. bath chart in QQ-P-35 assigns only type II, not type VI, to 303, but I suspect that type VI is probably okay. citric acid based passivation works well also.

I assume there are some rinses after the passivation bath that you just left off your list.

I don't recommend the use of hydrochloric acid on stainless steel.

All things considered this should be a decent process. I think you need to determine if you have an iron oxide problem or a sulfur problem. You can usually tell the difference under magnification, rust looks jagged while sulfur looks blobby. Or dip a part in alkaline cleaner (pH of 11 or so), if the brown stains go away, it is sulfur.

Let us know if we can help you.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner




(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully 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 might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact  -  Privacy Policy  -  ©1995-2024 finishing.com, Pine Beach, New Jersey, USA  -  about "affil links"