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yvi
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Join Date: Nov 2007
Posts: 31

Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/27/2009 4:26 AM

Hi Hello Everyone,

Just want to know...

What is the best chemical to be used in Passivation of stainless steel, Nitric Acid or Citric Acid?

Will there be a notable difference in the material being passivated using Nitric Acid or Citric Acid?

Thanks in advance.

yvi
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sb
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#1

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/27/2009 11:33 PM

Both the methods are acceptable.

The Citric Acid treatment has the advantage of less hazardous.

The Nitric Acid based pickling is covered under ASTM A380 ( Practice for Cleaning, Descaling and Passivating of Stainless Steel Parts, Equipment and Systems). BS EN 2516 also is basically Nitric acid based with some variations (eg addition of Sodium dichromate)

ASTM A967 ( Specification for Chemical Passivation Treatments for Stainless Steel Parts )covers both the Citric Acid as well as Nitric Acid based treatments.

However ensure the SS to be pickled since the nascent H released during the pickling are adsorbed by some of the SS leading to hydrogen embrittlement.

Check this link

http://www.euro-inox.org/pdf/map/Passivating_Pickling_EN.pdf

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Isti80
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#2
In reply to #1

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/28/2009 7:08 PM

Just out of curiosity what household acid (if any) can be used to passivate SS with? Is vinegar good?

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sb
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Join Date: Mar 2007
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#3
In reply to #2

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/29/2009 12:51 AM

Citric acid is a house hold acid (regularly ised for curdling milk) and is lemon juice (of course refined - like sugar cane juice Vs Sugar)

Vinegar - Acetic Acid.

Searched the "SS Pickling Acetic Acid" and there are some results however not sure whether the codes will permit.

Got a good link here (not for acetic acid)

http://www.bhavini.nic.in/Attachments/c60C%202.%204%20%20%20%20%20PFBR-01940-SP-1000.pdf

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zoowho2
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#10
In reply to #3

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

06/09/2009 4:58 PM

mastrsmth: ( Am told and have used, apple cider vinegar for disolving uric acid crystals formed in gout locations. A couple teaspoons full 3 times a day, began eliminating them within 1 day. Take teaspoon of honey to coat throat and taste buds and toss down vinegar or dilute with water....but, the less I have to toss the better I dislike it.
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hazman
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#8
In reply to #2

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/31/2009 5:13 AM

I doubt if any organic acid would affect Stainless Steel. Citric acid attack or vinegar (acetic acid) attack would rule out their use for cooking utensils.

Note one picking solution contains Hydrofluoric Acid - perhaps the most powerful (dissolves glass)

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RHABE
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Location: Germany 49° 26' N, 7° 46' O
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#4
In reply to #1

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/29/2009 12:56 PM

Thank you for a very good link,

especially the tests for residual iron is of value!

GA!

Some procedures to be updated:

Any use of chromium IV is banned now with only a very few exceptions!

RHABE
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yvi
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Join Date: Nov 2007
Posts: 31
#6
In reply to #1

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/29/2009 8:14 PM

Hi Sb,

Thanks for the link you provided.

GA for u..

Its very useful

Regards,

Ivy
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Aviator
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#7
In reply to #1

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/30/2009 10:00 AM

Just a note : vinegar is really very weak acetic acid. A much stronger concentration was available to mix with water for the "stop bath" in black and white photography (the bath following the developping bath). Might still be available for that purpose.
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ChemE119
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Location: michigan
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#5

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

03/29/2009 5:54 PM

Citric is also less corrosive to steel than Nitric or other acids!
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zoowho2
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#9

Re: Nitric Acid or Citric Acid for Passivation of Stainless Steel?

06/09/2009 4:53 PM

I don't have the foggiest idea.......................

But I can tell you, a teaspoon a day of citric acid will prevent kidney stones. Taken with a teaspoon of olive oil or mix in a citric juice, and toss it down fast. It will prevent kidney stones. Proven to myself over the years from a tip given to me by an old euwell gibbons type guy from Hyder Alaska, I thank him again. It works!
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Aviator (1); ChemE119 (1); hazman (1); Isti80 (1); RHABE (1); sb (2); yvi (1); zoowho2 (2)

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