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Passivation in citric acid

2007

Could anybody help us for performing the passivation in citric acid?

We have experience of passivation in nitric acid, but not in citric acid , and we bought the ASTM A967 & ASTM A380 for our study. In the ASTM A967 appendix, we found the figure of recommended nitric acid passivation 1 - 5 treatment for different grades of stainless steel.
Then, we would like to know if this chart is applicable to the passivation in citric acid 1 - 5 in the same manner or not.
The material we mainly use is AISI304.
It would be also appreciated if anybody could indicate the best practical way of passivation treatment in citric acid for 304 stainless steel.
As passivation in citric acid is not common in Japan, it would be highly appreciated if anybody answer my question.

Thank you for your help.

Atsusshi Okubo
product designer - Tokyo, Japan

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The article 'HOW TO PASSIVATE STAINLESS STEEL PARTS' by Carpenter Technology gives both citric & nitric acid passivation procedures for the various stainless steel grades: crswnew.cartech.com/wnew/techarticles/TA00042.html

Passivation using simply citric acid + water is often considered inferior to that using nitric acid. Commercial citric acid passivation solutions containing proprietary additives give better results. E.g., see Letters 28680 39330. Vendors such as Stellar Solutions [a finishing.com supporting advertiser] furnish instructions with their products and on-line.

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.
2007

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Thank you for the information.
I read the articles and the letters indicated.
We will try the procedure instructed in the article, though passivation in citric acid seems not helping oxidizing the surface.
I understand that the passivation in citric acid and then rinse with DI water or adding other oxidizer in the water will help the stainless steel to be passivated in the same way as nitric acid do.
Is my understanding correct?

Atsushi Okubo
- Tokyo, Japan
2007

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2007

Commercial citric acid -based passivation solutions contain proprietary additives. These may include: cleaner, surfactant, oxidizer, and corrosion inhibitor. Use a commercial product such as Stellar Solutions [a finishing.com supporting advertiser], at least until you understand the chemistry.

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.

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Thank you for your information.
The commercial solution seems fine, and I will contact them.

Atsushi Okubo
- Tokyo, Japan
2007

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New ASTM A967 replacing QQ-P-35C is only adding on the citric acid but referring ASTM A967 standard, both of the acids also call for passivate when applying chemical.
My doubt is, if both of the acids is the same solution and how come both of the acid also called out in this standard? Is it both of the acid also can be used when applying the chemical during passivate? --the standard of ASTM did not spell out clearly on this.
Appreciate someone can explain more clearly on my doubt.
Thanks and have a nice day.

Tan Teng Cheang
Supply Chain Management - Bayan Lepas, Penang, Malaysia
2007

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Passivation may be done with either a nitric acid bath or a citric acid bath. citric acid passivation systems were developed as an alternative to nitric acid, one that provides as good or better results with much less hazardous chemistry. There is no reason to use both.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2007