Stefan Trethan wrote:
> On Tue, 28 Jun 2005 13:57:56 +0200, Adam Seychell
> <a_seychell@...> wrote:
>
>
>>If tools are corroding several meters away then it must be HCl gas,
>>rather than splashes or wouldn't travel so far. What etchant are you
>>running ? There should be almost no oder from a open jar of etchant at
>>room temp. Keep HCl concentration under 2 Molar. If your stuck with a
>>fuming etchant,(i.e an open container of etchant will corrode steel in
>>its vicinity) then you have to keep it sealed. All I can recommend is
>>keep the place well ventilated during etching, and seal air tight when
>>not in use. You must of course also eliminate exterior splashes due to
>>bubbles.
>
>
>
> I use CuCl, but maybe my fumes fear needs explaining:
>
> Years ago, when i still used HCl H2O2 Tray etching with way too high
> concentrations of all, i forgot a small etchant tray on a workbench with a
> nice new set of drills (and other stuff) about half a meter away. After
> several days (maybe even weeks) when i discovered the situation the drills
> did not look new any more :-(.
>
> This was a open tray, and i haven't discovered problems with my etcher
> (rubber seal, but not really airtight just a lid) so far. There is no odor
> with the current etcher when it is just standing around, but when the pump
> is pumping like 100l/h of air through those 100l will have some fumes in
> them and will definitely leave the etcher.
> On another occassion i discovered it is not good to store steel spray cans
> near a closed PE bottle of HCl, the can seam started rusting. This was
> after months.
>
>
> I will put a few experimental nails around the etcher, and try to put all
> tools further away, then it will be fine to run open-loop i hope. When any
> of the nails start to rust i must do something.
Thats a cleaver test. The HCl is weired in that low concentrations <
0.1M won't release any HCl. Yet, if the concentration is high then HCl
likes to escape. You can see this at the extreme when opening the lid of
a bottle of the concentrated acid.
So by lowering the acid say by half, you can dramatically reduce the
release of corrosive fumes. I'm not sure of the exact concentration you
used initially that reduced your drill bits into rust, but going by your
description I could easily see this happening.