Cleaning copper wire 1

[sbkenn]

Hi. Another off-beat question. Can anyone recommend a material, probably a liquid (acid or base ?), which will effectively remove oxide from a heavy stranded cable. Soldering flux is not an option, as the cable is about 100mm^2/.15in^2, stranded. It is also rubber insulated, so heating is not an option. I want to clean it before clamping a connector, and sleeving with glue-lined heat-shrink.

Thanks-in-advance

 

[ScottyUK]

Is it definitely oxide? Copper oxide is black or deep red depending on the valance state. If it's green then it's probably a sulphate or carbonate complex.

 

[VEBill]

An acid of some sort. And you'd want to make sure it's fully removed after.

Standby for confirmation from others!

 

[jraef]

Even if it is copper oxide, what is the concern here? If this were data cable where tiny differences in resistance might be an issue, maybe. But for something this big, the copper oxide layer that forms on bare copper conductors is not going to exceed maybe 1000 angstroms in around 3 years before it stops itself, and at 1000 angstroms, you are looking at a resistance of maybe 75 milliohms added to your connection. Sneezing while clamping your connection lug would have a lot more of an effect.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[sbkenn]

Must be sulphate then. I am more concerned about cleaning it before I seal the connection than actual, real and present resistance. It is furry sulphate though, in a small wooden ship. I will have a pair of these cables running the full length (106ft), for minimal voltage drop, with bronze connectors where I need to join them.

 

[jraef]

Ah...
3 step process I learned from the fishing fleet electricians in Seattle:

Step one, dip and swirl the stripped end of the wire in a solution of one tbsp of salt and 2 cups of liquid muratic acid (swimming pool acid) until the green or white crud goes away.

Step two, dip and swirl in a container of 2 tbsp of baking soda and 2 cups of water for about 1 minute to neutralize the acid.

Step three, dip and swirl the wire in distilled water to clean off the baking soda residue.

Allow to thoroughly dry before using, use a blow dryer if necessary. It might oxidize to a dark color quickly after this, but don't worry about that.

Every 10 or so connections, throw out the acid and distilled water and start over with new batches, you can just keep adding baking soda to the other container until it get too thick, then start over.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[davidbeach]

What? "Throw out" an acid bath with heavy metal contamination? Don't you understand the hazmat disposal rules?

Probably an awful lot of that back in the day, but serious trouble today.

 

[ScottyUK]

In a marine environment it could well be a copper chloride, seawater being the source of chloride ions. Similar colours to carbonate and sulphate.

jraef's cleaning method is interesting - it's similar to the 'pickling' process used by metalworkers to clean and de-scale copper and brass before things got all boring and safe.

 

[sbkenn]

Thanks jraef. In my case, it would be a cupfull of liquid being discarded, the chlorine would come from the sea, the acid is common anyway. What do people do with swimming-pool-water when they empty their pools ? The only other toxin is copper ... a few micrograms of it. Pickling, as I have come across it, is used to treat Stain-less steel after welding, and that acid is washed down the drain.

 

[moltenmetal]

Copper isn't typically considered a "heavy metal", though it is a phytotoxin- in high concentrations. When you're ready to dispose of your "pickle liquor", just mix (carefully, slowly) the baking soda mixture with the acid mixture. Pre-dilute with water if necessary to keep the heat of reaction from getting out of hand. Continue to add baking soda (you will likely need more than is in your remaining solution) until it no longer fizzes, then dispose of the mixture down the drain with lots of water- or into the ocean. The TINY amount of copper we're talking about here will not be a concern to anyone, or any marine life, unless you start doing hundreds of connections.

I'd consider adding one more step: I'd tin the end of the wire after cleaning it and before drying. Don't do this by soldering, assuming this is a THICK cable and you're worried about damaging the insulation. You can buy an "elecroless" tinning solution which is intended for coating the copper on circuit boards. This will keep the oxidation and hence the contact resistance, lower for longer than it would be otherwise. Don't want to tin? There are corrosion protection greases intended for electrical connections that can be used instead. They typically use zinc particles in the grease as a sacrificial anode.

 

[jraef]

Or use vinegar... All "natural" that way.

I was told you can make oxalic acid by boiling rhubarb leaves and use that. Never tried it though. Almighty Google might be able to check the veracity of that, but I'm too lazy now to check.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[sbkenn]

I have a pot of chemical-deposition tin that I bought 20 years ago, but never used. I could also electro-plate with nickel.
Acid plus base -> salt ... of some sort. I probably scraped more copper (40 year-old anti-fouling) off a square inch of my hull than I would flush in with this job. I may just use copper loaded grease, then seal with heat-shrink.

 

[MacGyverS2000]

Those tinning crystals (where a solution is made from them) go bad after a year or two, if memory serves... the solution goes bad even more quickly.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[sbkenn]

Forwarned
I will reserve it for things (if it ever happens) which will be soldered immediately.