Pickling & Passivating

Question

Pickling & Passivating

SIAUPA (Mechanical)

(OP)

7 Jan 04 13:21

Could somebody confirm this statement:
If a surface is passivated, it is understood that was previously pickled. Therefore in saying a surface is pickled and passivated, the word pickling becomes redundant.

Is this right?

bmoorthy (Mechanical) · Answer 1 · 2004-01-11 11:22:13

No take a look at ASTM 380, for details and clarity/definition.

Division (Materials) · Answer 2 · 2004-03-05 08:27:01

look at this link
http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/A380.htm?L+mystore+rzlm9020

1969grad (Mechanical) · Answer 3 · 2004-03-06 02:19:03

When people use the term pickling they really refer to the whole process which includes passifying.  Sort of a short cut nominclature.

Pickling is the acid bath to remove mill scale etc.  Passivifying is another chemical to neutralize the acid.

A speciality contractor will first circulate a acid through the piping for pickling followed by circulating another chemical to neutralize the acid.  Then the piping is dried and sealed until it put into service.  As I recall Dowell was one company who could provide this service on site.

Pickling of piping is now rarely done in the US because of the environmental problems with disposal of the chemicals.

In the 1960s and before engine manufacturers used to use carbon steel pipe for LO and fuel gas and then pickle the piping.  Now they use SS which does not need to be pickled.

Do not know your application but I would recommend you avoid the pickleing process by selecting another material for the piping.

All of the above assumes you are concerned about dirt, mill slag, etc. on the inside of the pipe and not the outside surface.

PS  Sorry for the spelling but spell checkers were made for people like me.

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Pickling & Passivating