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Old Etching solution

Discussion in 'Electronic Design' started by Jamie, Jan 1, 2011.

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  1. Jamie

    Jamie Guest

    At work, when I do a board I can use their disposal services
    rid the old etching solution.

    For those that also do this at home in the US, what methods are
    used in your area's to depose of such chemical? Recently work has
    been complaining about people using their disposal services for home

    I used to dilute it to a safe level and flush it how ever, this
    stuff really stains and the wife does not like it. We do have a
    oil, antifreeze etc. place, at our transfer station. Do you guys send
    the depleted etching there?

  2. mike

    mike Guest

    Oregon has "neighborhood hazardous waste days". They show up at a school
    parking lot and accept residential quantities of stuff for safe
    They thank me for accurate labels on all the nasty stuff I take
    and have never refused to take anything.
  3. Nico Coesel

    Nico Coesel Guest

    If you use ferric chloride as etchant you can reactivate it by adding
    HCl (hydrochloric acid). You never have to dispose it until you want
    to get rid of your etching gear.
  4. interesting.

    Is there some easy trick to know how much HCl to add to regenerate your
    solution, and how to get the copper junk out after doing so?
  5. Jamie

    Jamie Guest

    Hmm, I've never heard of that before. Maybe I should give that a try.

    Now, where would I buy this off the shelf in small quantities. :)

  6. Tim Williams

    Tim Williams Guest

    Not completely. The copper junk in solution slows it down.

    Etching only works if the stuff can stay oxidized. If you don't use it
    much, and leave the container open between uses, it will oxidize fairly
    well from atmospheric oxygen. Otherwise, adding an oxidizer such as
    bleach (sodium hypochlorite), sodium chlorate or hydrogen peroxide, slowly
    and with stirring and ventilation (mind the release of chlorine gas!),
    will oxidize it back.

    Oxidizers will also enhance the etch rate. This is true even of pure
    copper chloride (which is the main byproduct of ferric chloride etching),
    which etches very slowly, in and of itself.

    To remove the excess copper, you have to completely reduce the solution.
    The best way to do this is soaking scrap iron in the solution, which
    precipitates copper metal and reduces any remaining ferric (adding more
    iron to the solution). The resulting ferrous chloride solution must be
    oxidized first.

  7. A pool supply shop will have HCL on hand, by the Gallon.

  8. amdx

    amdx Guest

    I was told, " The solution to pollution is not dilution"
    But as I recall the radio shack etchant bottle said dump it down the
  9. Guest

    Vermont had a truck that came around to the dumps every quarter or so, for the
    weekend. They'd take any household chemical, including paints. If you didn't
    want to wait for the "Rover", you could take the stuff down to the main office
    anytime during the weekday. I don't know what we do here. Haven't had
    anything like that to get rid of, yet.

    Paints can be left to dry and then thrown in the trash. Adding some kitty
    litter will speed up the drying. Paint stores also sell a chemical that can
    be added to paint to speed up the solidification.
  10. Nico Coesel

    Nico Coesel Guest

    Over here: most drug stores and pharmacies sell HCl in 10% strength.
    When ferric chloride gets saturated a yellow sludge forms at the
    bottom of the tank. Add HCl until that disappears.
  11. Guest

    AKA Muriatic Acid.
  12. Mark Zenier

    Mark Zenier Guest

    _Electronic Prototype Construction_ written by Dr. Barry Ornitz'
    co-worker at Eastman Chemical, Stephen Kasten , says to add it to
    mortar mix and send the lump to the landfill.

    Mark Zenier
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
  13. amdx

    amdx Guest

    So what is the procedure?

    Do I reduce it with iron.
    Add HCI
    Then add bleach to oxidize


    If I reduce it with iron
    Do I skip the HCI
    Then add bleach to oxidize.

    I have had three or four bottles of used Radio Shack Ferric Chloride
    on the shelf for at least 5 years. Can I make it work again?

    PS. Don't try to warm a glass container full of Ferric Chloride on your
    wife's SS burner covers.
    The glass cracked and FC leaked through the crack and etched a long line
    into the burner cover.
    Luckily I noticed the problem before making a huge mess out of the stove.
  14. Guest

    Like many things, its hazmat status likely depends on the quantity.
  15. Nico Coesel

    Nico Coesel Guest

    Not really. You always lose some liquid due to evaporation. In my
    experience you don't need a lot of HCl to reactivate FeCl.
  16. Tim Williams

    Tim Williams Guest

    You need enough HCl to dissolve the iron gunk, and dissolve the iron
    you're adding, AND accommodate the oxidation.

    HCl first, then iron. When all copper is precipitated and the iron is
    dissolving with the production of hydrogen, the solution is completely
    reduced. Run through a filter and begin oxidizing it. If the solution
    becomes turbid, add more acid to keep it in solution.

    I would recommend using 30% H2O2 because bleach is basic, adds sodium, and
    reacts quickly, resulting in lots of chlorine gas, even if you stir it in

    Sodium chlorate reacts slowly as well, which can be a problem because you
    can easily add too much. Although it adds sodium, it doesn't add as much
    as bleach does. It can sometimes be found as all purpose weed killer,
    particularly in Europe.
    Uh... good idea not to heat a glass container of *anything*. For that
    matter, even using glass ovenware these days is risky. Pyrex isn't
    "pyrex" anymore.

  17. It is much better than ferric chloride. It also has a great advantage that
    it won't etch nickel or solder plated traces that allows for making
    plated-through holes.

    Unfortunately it has one _MAJOR_ deficiency -- the etching solution don't
    last. It is OK for manufacturing when solution is discarded at the end of
    day but for a hobby use when one board is etched once a month or so it is a
    big waste.

    The best one for hobby use is cupric chloride. It is cleaner than ferric
    chloride and the solution lasts forever. Dunno how it works on nickel/solder
    plated copper but usually it is not an issue in hobby use because it almost
    never involves PTH that requires much more chemicals and those chemicals are
    quite expensive and not all of them are readily available for a hobbyist.
  18. Guest

    That's just stupid, though wouldn't expect otherwise from the weenie left
    (coast). There is *nothing* in paint that will harm a landfill, particularly
    once dried. Nothing to spill on the way to the dump, either.
    The only good one is to *MOVE*.
    ....and have the Secret Service throw them all over your yard and write the
    strongly worded subpoena?
  19. Guest

    Utter nonsense.
  20. That sounds like a problem, not a solution.

    [Ho Ho!]
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