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Jon Lorber
 
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Default Etching 304 Stainless Steel with Ferric Chloride Problems

Thanks for the info! Can you post here if you finish the FAQ? The liquid
resist that we use on stainless is called Hydro-coat. It's super expensive
but doesn't come off very easily at all. In fact we use either an aircraft
stripper or sand it off.

Jon



"Xane T." wrote in message
...
On Mon, 05 Apr 2004 17:02:26 GMT, "Jon Lorber"
wrote:

snip


I should finish up the metal etching FAQ that I'm working on. Since
it's not my main business anymore, I can drop this hint at least. You
can regenerate Ferric Chloride with air bubbling and muriatic acid for
about 3 refresh cycles. After that, it will become way too saturated
with whatever you're etching in it. For copper/brass, the copper
chloride will eventually crystalize into rings of needle crystals at
the bottom of the tank. I would reccomend chilling your spent etchant
to attempt to force more of the contaminant out of the solution. After
that, you can regenerate what's left with 40 volume hydrogen peroxide
from a hair salon [try Sally Beauty Supply]. Clairol hair bleach has
nothing in it but the peroxide [some other brands have
cleaning/foaming agents]. Make sure the etchant is in a heatproof
container, I use a 3.5 gallon bucket inside of a 5 gallon bucket in
case the bottom drops out. This causes a pretty violent reaction
[foaming], so make sure the container is less than half full and add
it slowly, stirring constantly with something like an acrylic stick. I
use about one 16 oz bottle per gallon of etchant. You /could/ use 100
volume peroxide if you can get it, but the reaction may be extremely
violent at that concentration. This /does/ produce hydrogen gas, so
you need to do this outdoors and be careful with it. Then let it air
bubble overnight using an aquarium pump or something. This seems to
force the FeCl2 back into FeCl3. I don't measure baume or ph, but it
changes etchant that took six hours to etch through a sheet with no
agitation into a 2 hr job, which is a little longer than 'fresh'
etchant. This has only been tested with etchant that's used with
brass, but you can try it with stainless [I have yet to find a resist
that will stay on the steel so I can't do steel etching yet]. You can
also buy dry ferric chloride to add in if it doesn't seem strong
enough, but don't add as much as if you were mixing it with water.
It's still a lot cheaper than buying new etchant. You will need to use
peroxide for each future regeneration, while keeping the pH up with
muriatic acid. If you have testing equipment, then you can probably do
a better job at finding out what ratios of each chemical to use than I
do [I'm just a hobbyist].