[spartan]

Hi all,
Here's my first post with a question I've been trying to solve for a while.

I work with electronic components of very high quality and we try to make all our connections using thin copper ribbons of various thickness. I have started cleaning my copper connections with a solution of vinegar and salt (more or less 3g of salt in 200ml vinegar). I believe that combination yields sodium acetate and hydrogen chloride. It gets rid of any oxidation on the copper. Even copper that looks very clean appears much brighter and cleaner when the solution is applied.

My problem is what happens after the procedure: the piece of copper after a while becomes much more oxidized than before (the new oxidation starts to become visible after a few hours). I have started to clean the copper with isop. alcohol, which sometimes works well, and sometimes doesn't. I suspect the piece must be scrupulously cleaned in order not to oxidize again (in the rate described), which is sometimes very difficult. (Let me add that this is a problem because often I must clean the parts a couple of days before soldering them, and in other cases the connection is merely mechanical).

My question is whether any good soul here would know how to "neutralize" the sodium acetate/ hydrogen chloride solution right after it has cleaned the copper. The reason why the copper oxidizes really fast if I don't clean the solution with alcohol and why it doesn't when I do is beyond me. At any rate, I am looking for a more practical way to maintain the copper bright and clean after using the vinegar solution, for as I said cleaning it with alcohol is very time consuming in order to be effective.

I thank you all in advance for any *delete me*

Marcel

[Intanjir]

I recall that chloride ions do not play well with copper and that the removal of chloride is one of the principal goals of copper restoration.
Basically, any residual chloride ions will continually disrupt copper's ability to effectively passivate itself.
It is therefore generally recommended that copper be cleaned without chloride.

Wikipedia lists a number of potentially more suitable cleaning solutions:
https://en.wikipedia.org/wiki/Conservation_and_restoration_of_copper-based_objects#Conservation

[Borek]

If memory serves me well CuCl (as apposed to CuCl₂) is a culprit here.

[Intanjir]

Very informative page on copper restoration:
http://nautarch.tamu.edu/CRL/conservationmanual/File12.htm

I wonder whether cleaning electrochemically would be preferable to a chemical cleaning agent.

[Enthalpy]

As an e.engineer, I would NOT put salt at electronic circuits, and prefiribly water neither - vinegar is mainly water. Chlorides ions are badly corrosive to metals, while sodium ions are deadly for semiconductors, and for instance plastic packages don't stop sodium ions. Additionally, even the slightest trace of salt on a printed circuit botches the insulation resistance.

If salt water came in contact with an electronic circuit, you should rinse with plenty of tap water, then with destilled water, then with absolute alcohol to remove the water.

Copper will not stay clean in the normal atmosphere. Traces of chlorine ions accelerate its corrosion. The proper way to keep a clean surface is to cover copper with a better alloy, for instance with solder, tin, nickel, palladium, gold...

Slightly tarnished copper can still be soldered. That's the role of the rosin flux in the solder wire. Satellite manufacturers have got it wrongly, and instead of rinsing the flux after soldering, they use solder wire without flux, hence have difficulties at soldering, and bad contacts. Too bad for them.

If the shape of the copper parts to be cleaned permits it, by far the best cleaning method is mechanical. Take the rubbing side of a sponge, rub a bit, done. On flat surfaces, even an eraser can give good results.