A opposed to a black powder coming off, wouldnt the gold just form chloroauric acid with the HCl? This would save money, using a cheaper acid and skip a refining step. If not, why is sulfuric acid absolutely nesscessary? I am trying to deplate decorative stainless steel pieces, with a nickel and copper undercoating that id prefer to leave behind.
Can I use HCl in place of H2SO4 for a gold deplating cell?
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My thoughts are No, it won't work. I am not sure what is expensive, but sulfuric acid here is only about $18 a gallon. Less if bought in bulk. Set up and ran properly, a gallon can remove a lot of gold, way more than $18 worth. Hydrochloric acid exposed to air will start attacking your nickle and copper. It can become more aggressive than sulfuric at the right concentrations. Keep the moisture from your sulfuric acid, and keep the heat down, and it will work well for removing the gold. If you wish to re-plate the parts afterwards, I can't be of much help there and the sulfuric cell may not be the best method either.
Besides the electrolyte forming dangerous chlorine gas.
In the chloride cell the nickel, copper, and gold would ionize and then just plate out (or be reduced together) on the cathode, so your not separating the metals.
In the concentrated sulfuric cell, the depletion of electrons of base metals such as copper at the anode is more limited, making removing the gold plating easier without attacking the base metals as much, the base metal ions, the base metal atoms that were oxidized (dissolved) into the ionic form will stay in solution when the electrolyte is diluted as sulfate salts of the metals dissolved into solution. The gold plating the gold atoms are only temporarily oxidized (only a temporary loss of electrons from the atoms of gold) dissolved into an ionic form upon losing electrons at the anode, and again the gold ion is soon reduced back into metallic gold as soon as the gold ions leave the anode area on their journey towards the cathode, basically giving you a way to separate the metals...
As with any of these processes of recovery or of refining of metals, I would spend my time studying about it thoroughly, doing so you begin to understand how and why they work, why they may be chosen over another process, to gain a better understanding of the dangers, and any problems that are normally encountered as well as how or why the process may be viable for the material I have, the more you understand the more you see why a certain process may or may not work and why...The more you understand a process the fewer problems you will have when you begin experimenting to learn those processes...
In the chloride cell the nickel, copper, and gold would ionize and then just plate out (or be reduced together) on the cathode, so your not separating the metals.
In the concentrated sulfuric cell, the depletion of electrons of base metals such as copper at the anode is more limited, making removing the gold plating easier without attacking the base metals as much, the base metal ions, the base metal atoms that were oxidized (dissolved) into the ionic form will stay in solution when the electrolyte is diluted as sulfate salts of the metals dissolved into solution. The gold plating the gold atoms are only temporarily oxidized (only a temporary loss of electrons from the atoms of gold) dissolved into an ionic form upon losing electrons at the anode, and again the gold ion is soon reduced back into metallic gold as soon as the gold ions leave the anode area on their journey towards the cathode, basically giving you a way to separate the metals...
As with any of these processes of recovery or of refining of metals, I would spend my time studying about it thoroughly, doing so you begin to understand how and why they work, why they may be chosen over another process, to gain a better understanding of the dangers, and any problems that are normally encountered as well as how or why the process may be viable for the material I have, the more you understand the more you see why a certain process may or may not work and why...The more you understand a process the fewer problems you will have when you begin experimenting to learn those processes...
butcher said:
thats an excellent explanation and exactly what i was worried would happen. thank you so much! like was said below, sulfuric isnt much more expensive, i suppose ill have to take a trip down to ACE hardware. Now to make sure i dont give myself nickel poisoning...
If you have the right set up ie a fume hood reverse AR is a good route, if you do not know what I’m talking about then it’s cover the material in nitric and add very small increments of HCl to dissolve the gold, do not be over generous with the HCl and the nitric will passivate the stainless only removing very small amounts.
