Materials & Welding: RE: [MW:32316] Is there any difference in performance between pickling and passivation?

Tuesday, April 20, 2021

RE: [MW:32316] Is there any difference in performance between pickling and passivation?

Hi,

The term Pickling(in the context of Carbon and other low alloy steels) often refers to acid clearing, which may be done prior to application of paints. Usually for mass production spray painted items it's a common practice. Pickling usually descales the steel, exposing clean surfaces for spray painting. Pickling may cause some passivation of the cleaned surface, through formation of Cr-Oxide. However as C & Low Alloy Steel contains very little or No "Cr", chances of passivation are minimal.

In the context of stainless steels and other high alloy steels, both "pickling and passivation" occurs simultaneously due to the high extent of alloying elements, especially "Cr". Nickel based alloys pickle and passivates to lesser extents that Cr-based alloys , e.g., 300 series or Duplex or other stainless steels.

This attached literature explains the various aspects of pickling, passivation and associated techniques.

Thanks.

Pradip Goswami.P.Eng, IWE.

Independent & Consulting Welding & Metallurgical Specialist

Linkedin: https://www.linkedin.com/in/pradip-goswami-2999855/

Email:pgoswami@rogers.com,pradip.goswami@gmail.com

Cell/Whasapp:1-905-9793232

From: materials-welding@googlegroups.com <materials-welding@googlegroups.com> On Behalf Of Ananthanarayanan Mohan
Sent: April 20, 2021 7:07 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:32315] Is there any difference in performance between pickling and passivation?

Dear sir,

Pickling activates the surface for proper plating. Hence is used in many plating works. It removes the stains scales etc and provides the surface ready for uniform reaction to form the required layer of plating Passivation on a pickled surface provides a uniform layer of oxides resistant to corrosion. Well, the doubt may be whether you require both treatments.

A chemical pickling agent made from nitric acid and hydrofluoric is applied to a surface to remove contaminants. The hydrofluoric removes the contaminants while the nitric acid aids in activating the stainless steel surface to promote passivation. ASTM 967 gives passivation for stainless steels with nitric acid and citric acid. Pickling as such is not mentioned. But in case of fabricated parts used in fatigue intensive applications that has undergo salt spray tests pickling is useful to remove all contaminants.

thanks and regards

Mohan Ananthanrayanan

Consultant special process, Aerospace manufacturing

+91 9496070045

On Tue, Apr 20, 2021 at 6:33 AM pravean ashok <gujulapravean@gmail.com> wrote:

Dear sir

Please find the below link

https://youtu.be/nqBLsPM88dk

Regards
Pravean

On Tue, 20 Apr, 2021, 2:21 pm Kannayeram Gnanapandithan, <kgpandithan@gmail.com> wrote:
Any Acid used in Passivation

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On Tue, Apr 20, 2021 at 1:09 PM pravean ashok <gujulapravean@gmail.com> wrote:

Pickling is a matal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust contamination or scale
A solution called pickle liquor, k2 chemical paste which is usually contains nitric acid, is used to remove the surface impurities. It is commonly used to descale or clean steel in various processes.

Passivation
Passivation is a chemical treatment for ss and other alloys that enhances the ability of the treated surfaces to resist corrosion
Passivation removes surface contamination
Passivation increase corrosion resistance
Passivation reduces the risk of product Contamination
Passivation allows you to extend system maintenance intervals

On Tue, 20 Apr, 2021, 10:59 am PK M, <pkmqaqc@gmail.com> wrote:
Dear All,
Please Explain

Is there any difference in performance between pickling and passivation?
Thank you
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