Low cost copper etchant

[macfixer01]

I spotted this info on Instructables today regarding etching copper circuit boards using Vinegar, Salt, and Hydrogen Peroxide. I'm not recommending or anything since I never tried this, but just informing anyone interested of it's existence. I suppose he has a point though, compared to traditional etchants like Ferric Chloride or Ammonium Persulfate it is much cheaper and much less dangerous.

http://www.instructables.com/id/Is-the-best-PCB-etchant-in-every-kitchen-/

macfixer01

 

[solar_plasma]

Just for the completeness, it isn't less dangerous than CuCl2 or FeCl3. All soluble copper salts are toxic. Although vinegar is a weak acid, its vapor is bad for the lungs and concentrations above 25% are no joke anymore. Further, adding NaCl and H2O2, you aren't using harmless household vinegar anymore.

Nevertheless, it seems to be a valid method. Does anybody know the equations?

 

[Geo]

When I was young, I would use vinegar and salt to clean the coins I found while metal detecting. I was informed by a prospector friend of mine to never use it to clean nickles or German silver or it could kill me. I knew it released a toxic gas but never really studied on what it could be.

 

[solar_plasma]

I would guess, he said this because of the toxicity of nickel salts.

 

[butcher]

vinegar (basically dilute acetic acid)
Acetic acid CH3COOH.

Sodium chloride (table salt) NaCl.

Hydrochloric acid HCl.

Hydrogen peroxide H2O2.

Basically to me your just talking about making a dilute hydrochloric acid.

CH3COOH + NaCl --> CH3COO(Na) + HCl

We could go further with this formula, with H2O2 and copper, to show it all of the way to copper II chloride with copper, and the organic salts, but I think this gives you the idea.

As we know this HCl with copper and an oxidizer like H2O2 gives us Copper II Chloride.
But here you also have an organic acid in solution.

(Too strong or not the right concentration of the H2O2 and you also have gold in solution)...


I do not see any benefit at all to using this vinegar as a leach, as a round about way to make copper II Chloride to leach copper with(dilute) , full organic impurity's...


Even if I could not get HCl acid.
HCl is normally so readily available, Unless I was living in my cave.

In that case I would rather make HCl, using NaCl salt and H2SO4, distilling off the more pure HCl, and leaving me a useful byproduct. like sodium bisulfate or sodium sulfate, (depending on concentration of the sulfuric used).
Which I could also use that byproduct in other reaction.
Example for making ferrous sulfate (copperas) to precipitate gold with, using the sodium bisulfate to dissolve iron to make the ferrous sulfate, or copperas with...

Doing the reactions safely outside the cave of course, so I wouldn't smoke up my cave.

 

[solar_plasma]

Don't you think there is a side reaction and equilibrium to copper acetate, too?

edit: oh I see,you already mentioned the organic acid/impurity

 

[solar_plasma]

I just read about nickel carbonyl, even though it should not be generated in this case, it makes me think about the risk-gain-relation in chemistry and even something seemingly banal as welding/melting one more time. Scaring...