Corroded copper wire

[Wingeezer]

Many times when I have had to work on wiring in old hobby cars or RVs I have found stranded copper wire black with corrosion - even if I cut the wire back many inches from the exposed end, it is just the same.

In making a new connection to this wire, I have always splayed out the strands and scraped away with a craft knife to remove corrosion - that does not work well and the results are not good - it still will not accept solder well at all, and if you use crimp connectors probably does not make the best contact either.

Some time back, I was given info on this forum (forget who you are, but thank you!) about a way to deal with this.

(a) spread the wire strands out - soak a few minutes in a small amount of vinegar mixed with as much salt as will dissolve - I soaked for about ten minutes.

(b) neutralise the vinegar (a weak acid) by immersing the cleaned wire in water and baking soda (I used several tablespoons in an 8 oz bottle.). It only needs a minute or two swished around.

It seemed to work very well and I wish I had known of this when I renewed our brakes not too long ago.

Currently instead of soldering, I am now using weatherproof crimp connectors using the proper ratchet type crimping tool - seems to be the preferred method - but I'm sure that removing oxidation from the old wires is still desirable.

Yesterday, I replaced part of our umbilical cable as the plug was getting worn and unreliable.

I installed a marine junction box inside the storage box on our A frame behind the gas tanks and made splices to the original cable there.

I bought a new 8 ft cable with moulded on plug. This also allowed me to eliminate the short extension cable that I had to use with our Hensley hitch on teh original cable that was too short.

I used the method above to clean and prepare the original wires and have tried to attach a couple of pics to this post.

I suppose it would have been best to run a new plug and cable right into the trailer to the junction under the front sofa but the cable/plug I was able to buy at a reasonable price was not long enough - also, this way with the new junction box I added, it will be easy to replace again if ever I need to do so.


Couldn't seem to add the jpgs - Damn! the whole reason I wrote this! - you'll just have to trust me, it worked very well!

[uncle_bob]

Hi

Often the "black stuff" is more than simple oxidation. Some of the "good old" insulation materials turned out to be not so good for copper. That makes it tough to remove. It's combined with the copper to create some weird organic-copper compound.

Any form of acid removal is going to work like acid flux. It'll do a job on oxidation. It dissolves the crud (and the copper in it), the oxide (and the coper in it, and a bit of the copper it's self. What's left is less than what should be there.

It's also pretty much impossible to remove all the residue. What you create is a bit of a time bomb. The residual acid will eventually eat through some of the copper. As it does that the wire necks down even more. That increases heat and stress at that point. The probability of a break goes up as this happens.

Is there a *good* answer? Unfortunately, not really. The wire (at least the outer part of each strand) has turned into something else. It's damaged. This is one of the big arguments against stranded wire. (yes, there are a lot of arguments in it's favor as well). Replacing the wire is indeed a major pain ...

Bob

[Mollysdad]

I always tried to use "marine grade" wire. It's stranded copper, but then each strand is also tinned with nickel.
As I recall the cost is not that much more.

[Wingeezer]

Originally Posted by uncle_bob

Hi

Often the "black stuff" is more than simple oxidation. Some of the "good old" insulation materials turned out to be not so good for copper. That makes it tough to remove. It's combined with the copper to create some weird organic-copper compound.

Any form of acid removal is going to work like acid flux. It'll do a job on oxidation. It dissolves the crud (and the copper in it), the oxide (and the coper in it, and a bit of the copper it's self. What's left is less than what should be there.

It's also pretty much impossible to remove all the residue. What you create is a bit of a time bomb. The residual acid will eventually eat through some of the copper. As it does that the wire necks down even more. That increases heat and stress at that point. The probability of a break goes up as this happens.

Is there a *good* answer? Unfortunately, not really. The wire (at least the outer part of each strand) has turned into something else. It's damaged. This is one of the big arguments against stranded wire. (yes, there are a lot of arguments in it's favor as well). Replacing the wire is indeed a major pain ...

Bob

Thanks Bob,

In my case (sorry I couldn't post my before and after pics) The wire seemed to come out very clean - I did't try soldering it, as I was using weatherproof butt connectors this time, but I felt it would accept solder very well from the appearance. In the past when I tried vigorously scraping the oxidation off prior to soldering I still at best got a half-assed solder job!

I do think that most of what I was dealing with here must have been just oxidation.


As for residual acid continuing to eat away at the wires - I think that is what the dip in bicarb soda is for - ie t neutralise the weak acid (vinegar).


Anyway, we'll see how it goes - looks good for now!

[Wingeezer]

Originally Posted by Mollysdad

I always tried to use "marine grade" wire. It's stranded copper, but then each strand is also tinned with nickel.
As I recall the cost is not that much more.

Thanks - didn't know that was available! In this case though, i was splicing a new RV cable with moulded plug to the the existing cable on the AS that was just straight stranded copper wire.

[uncle_bob]

Originally Posted by Wingeezer

Thanks Bob,

In my case (sorry I couldn't post my before and after pics) The wire seemed to come out very clean - I did't try soldering it, as I was using weatherproof butt connectors this time, but I felt it would accept solder very well from the appearance. In the past when I tried vigorously scraping the oxidation off prior to soldering I still at best got a half-assed solder job!

I do think that most of what I was dealing with here must have been just oxidation.


As for residual acid continuing to eat away at the wires - I think that is what the dip in bicarb soda is for - ie t neutralise the weak acid (vinegar).


Anyway, we'll see how it goes - looks good for now!

Hi

I spent a lot of time trying to do this sort of thing. The acid wicks up the wire and combines with the crud. It more or less seals it's self off from whatever comes next.

I'm quite sure that it will solder after an acid dip. You have dissolved off the crud and the outer layer of metal. What's left is nice pure copper.

Bob