RE: Acetic Acid and 316l

From: <Bruce>
Date: Tue Apr 11 2006 - 09:18:00 EDT

AJ

My opinion is that you have provided (and probably only have) an incomplete or inaccurate "picture". If you have only acetic acid at pH 4.2 in an acceptable temperature range (I have no idea what "normal" is) in 316L, you will not have significant corrosion. If, however, the welds were done poorly resulting in metallurical changes, the heat affected zones might no longer be 316L, and corrode. 321 SS is strongly attacked by acetic acid (I've seen it before - a 321 pipe was supplied because the purchasing department could save some money, even though it was specified to be 316L). If the metal was passivated or "pickled" but inadequately cleaned afterward, the residual fluoride or nitrate (or other) could initiate the attack. If you have other things (such as chlorides, fluorides, etc.) that are also present only occasionally, corrosion occurs due to the "other things". There are many possibilties.

                            ... Bruce D. Bullough ...
                            Sebesta Blomberg & Associates, Inc.
                            2381 Rosegate
                            Roseville, MN  55113          USA
                            desk: 651-634-7344   fax: 651-634-7400
                            www.sebesta.com

-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=fjE22qo1c7AsrOaLE9jq5PeB3KswixqFwtNET67OCatS1AGNB-sucG2Or6F_H1p22qfkyp5DeTEc4VirqOahnAMioL0nBQ">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=fjE22qo1c7AsrOaLE9jq5PeB3KswixqFwtNET67OCatS1AGNB-sucG2Or6F_H1p22qfkyp5DeTEc4VirqOahnAMioL0nBQ">PipingDesign@yahoogroups.com</a>] On Behalf Of Arif Javed
Sent: Tuesday, April 11, 2006 2:04 AM
To: <a href="/group/PipingDesign/post?postID=fjE22qo1c7AsrOaLE9jq5PeB3KswixqFwtNET67OCatS1AGNB-sucG2Or6F_H1p22qfkyp5DeTEc4VirqOahnAMioL0nBQ">PipingDesign@yahoogroups.com</a> Subject: [PipingDesign] Acetic Acid and 316l [bayes][heur]

We have an vent scrubber made of 316L. This got corroded. Lab analysis showed presence of Acetic Acid 4.2 pH and acidity 0.25 wt %. Temperature is normal. My experience shows that this metallurgy should be OK for Acetic Acid. What is group's opinion?

   A J

Mechanical Engineer

[Non-text portions of this message have been removed]

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Yahoo! Groups Links Received on Tue Apr 11 09:18:00 2006