wackyvorlon - 25-10-2008 at 13:58
I was reading an article on salt water etching. This is a process where the piece to be etched is attached to the positive supply, and another piece
is attached to the negative. These are submerged in a saturated solution of sodium chloride, and voltage is applied. It occurred to me that this may
stripping copper ions from the anode, and producing copper chloride and sodium hydroxide.
I decided to perform an experiment. I made two copper electrodes, and diluted 72g of sea salt in 200ml of distilled water. I added a few drops of
phenolphthalein to this. I applied 13 volts DC across the two electrodes.
The solution turned deep magenta, and gas bubbled from the cathode. What appeared to be copper could be seen streaming from the anode toward the
cathode.
In my limited realm of understanding, this would seem to confirm the point. I am thinking of taking it further and filtering the solution, to see if
it produced copper chloride.
Can anyone give me any thoughts on whether I'm right?
12AX7 - 25-10-2008 at 14:09
Presumably, the substrate is copper. You didn't specify in the first case...
Because the solution is basic, copper will precipitate. In a concentrated solution of sodium chloride, copper goes into solution as the cuprous(I)
ion, which precipitates as yellow to orange cuprous oxide Cu2O when it reaches the basic solution near the cathode.
You can call it copper chloride, but because it's only transiently present in solution, it's not very realistic. The final product is the oxide, not
the chloride.
In a dilute solution, copper(I) chloride (CuCl) may precipitate, probably as a white residue on the anode. This can be oxidized in air to copper (II)
ions, which forms a mixture of the chloride and hydroxide. If the solution is well mixed, you should have the same results as before, that is, Cu2O
is precipitated.
Tim
[Edited on 10-25-2008 by 12AX7]
kclo4 - 25-10-2008 at 14:36
However, If you want Copper Chloride, You can react the oxide, or hydroxides that forms from the electrolysis with Hydrochloric acid to produce an
aqueous solution of copper chloride.
Foss_Jeane - 22-11-2008 at 15:46
Here's a web site that describes the process: Salt Water Etch Process for making circuit boards. It really does work. 
12AX7 - 22-11-2008 at 19:49
Bleh... "you have to cut the traces before it'll work", what a waste of time! I'll wire my boards point to point for that trouble!
Tim
chemrox - 22-11-2008 at 21:13
I went to the website and looked at some of the other instructions. There was one of rmaking NI3 that was not quite correct. I found some of the
other stuff to be pretty sloppy as well. What is an "eco button?"