Buffing of SS weld joints

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Hareesh K V

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Dec 3, 2019, 10:08:49 PM12/3/19
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Dear experts,
For after weld cleaning of SS weld joints my client insisted to do buffing on all the joints.

1. Is it a good suggestion?

2. Is there any technical argument so that we can avoid it?

3. Will buffing remove the passive layer and promote corrosion?

4. I got a comment that Buffing is a pickling activity and it should follow the preparation of not better not to go for buffing.

Presently we are cleaning the joints with SS wire brush after welding.

We don't have pickling and application in the scope of work and no need to for the same.

Thanks in advance.

Regards,

Hareesh K V

Kannayeram Gnanapandithan

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Dec 4, 2019, 12:03:36 AM12/4/19
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If u are not doing Pickling and passivation, Buffing is better. 

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Hareesh K V

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Dec 4, 2019, 2:55:07 AM12/4/19
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Dear Sir, 

Will buffing damage the passive layer of SS? 
Will it cause corrosion on a later date? 

Regards, 

Hareesh K V

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CAJzm4eOJ%2BD6xSTmVWS4VSiuvwpqZNxy71PNWv98EtnUQo59KUw%40mail.gmail.com.

Sudhakar Kuppuswamy

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Dec 4, 2019, 10:39:31 PM12/4/19
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Merely buffing will worsen the condition, it may give us a bright look immediately after buffing, but sooner or later we can able to see a uniform rust all around the weld joints.

 

In picking and passivation is not in the scope of work, and no painting system is applicable for those lines, from integrity point of view, it is highly recommended to carry out picking and passivation.

 

The situation will still go worse if the system is going get operated in high humidity environment, like sea-shore, offshore etc.

 

Anyway, the final call is with the client.

 

Regards,




Jaydeep

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Dec 4, 2019, 10:39:31 PM12/4/19
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Hello there,

No buffing will not damage passive film.
No buffing will not cause corrosion on later.

Please below ASTM A380 clause 1.1.1.1 (copy-pasted)
Passivation is the process by which a stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments. It was at one time considered that an oxidizing treatment was necessary to establish this passive film, but it is now accepted that this film will form spontaneously in an oxygen-containing environment providing that the surface has been thoroughly cleaned or descaled.

Hope it helps.

Regards,
Jaydeep Limbasiya
QC Engineer (Nuclear)

Ed Morden

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Dec 4, 2019, 10:39:31 PM12/4/19
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No


harenath jha

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Dec 4, 2019, 10:39:31 PM12/4/19
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Yes buffing is a mechanical work, which will definitely damage passive layer. However due to presence of cromium it will again form passive layer.

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Balajirajan Palanisamy

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Dec 5, 2019, 2:54:42 AM12/5/19
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Buffing is not advisable. Thorough cleaning,  Pickling and passivation is the best practice to avoid rust forming over SS weld joints.

Thanks and Regards,
P.Balajirajan.

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