The authoritative public forum
  for Metal Finishing since 1989
  

  -----

How to prepare passivation solution for SS304 fabricated parts to avoid rust

2006

We are facing a problem of Rust on SS 304 fabricated parts. These parts are meant for the use in Railway industry and most of these are brackets and nut plates.

Our suppliers are not very familiar with passivation process, so I want to know how to prepare the Passivation solution. Basically I need inputs regarding composition and mixing methodology.

Thanks,

Ajmal
- Dubai, UAE

---

2006

With 304 SS, a relatively simple passivation in 25-45 vol% nitric acid for 30 minutes at 21-32 C, followed by rinsing in clean water, is commonly used. The difficulty with fabrications is removing weld scale and cleaning prior to passivation. See ASTM ASTM A380 , 'Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems.' This also mentions methods to minimize iron contamination of SS during fabrication.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

---

Passivation with commercially available citric acid formulations according to ASTM A967 should give you what you need without exposure to hazardous chemicals. Contact us if you need help.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2006