[labnetwork] Anhydrous HCl after it escapes ...

[Weaver, John R]

John -
I've had experiences (certainly plural :)) with both external and internal leaks. For an internal leak, where moisture has gained access to the piping, I have always replaced the piping components up to the point where the leak was blocked - a valve, etc. I use valves with Hastelloy wetted surfaces (sometimes called Hastelloy trim), which is not impervious to HCl corrosion but certainly holds up better.
For external leaks, the key is to neutralize the surfaces as quickly as possible. In one instance we had to replace many components because we didn't neutralize the surfaces more quickly. A mild base works well for neutralization - something with a pH in the 9 range. Then a thorough rinse to remove any salts is necessary.
We run all of the gas cabinet exhausts for chloride gas cabinets through our plastic exhaust system, so we don't have to worry about exhaust. If you use a metal exhaust on the gas cabinet where the leak occurred, I'd carefully inspect the exhaust for a month or two after the incident.
I hope this helps.
John

John R. Weaver
Facility Manager
Birck Nanotechnology Center
Purdue University
jrweaver at purdue.edu
nano.purdue.edu
________________________________________
From: labnetwork-bounces at mtl.mit.edu [labnetwork-bounces at mtl.mit.edu] on behalf of John Shott [shott at stanford.edu]
Sent: Thursday, June 05, 2014 3:08 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Anhydrous HCl after it escapes ...

Labnetwork Community:

Sooner or later, it seems, anhydrous hydrogen chloride (or a number of
equally corrosive materials) is going to escape.  At least that is our
experience at the Stanford Nanofabrication Facility.  Despite our best
efforts to use quality components, do proper leak checking, etc., it
seems as if we end up with a leak either in a gas cabinet or in a tool
near a mass flow controller.  At that point, anything near the site of
the original leak has been covered with now moisture-laden hydrogen
chloride ... which, I believe, is far more corrosive than the original
anhydrous material.

For those of you who have encountered similar situations, how do you
recover or what to you replace?  Do you have effective means of
neutralizing those metal surfaces?  Do your replace VCR gaskets with
thicker-than-normal or grooved "super gaskets"?  Do you replace the
entire assembly?  Do you leak check, put back in service, and pray?

Thanks for sharing your experience and insights,

John


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