Removing oxidation from old wire

from a previous Post by texasSlick » Thu Jul 03, 2014 2:57 pm

While making a splice into the 50 year old wiring on my Atlas, I skinned the old wiring to find dull brown, oxidized, copper under the insulation. A crimp connection would have high resistance, and a solder connection would be near impossible.

I removed the oxidation by fanning out the wire strands, and dipping the wire ends in cartridge brass cleaner, producing shiny copper in minutes. The active ingredient is citric acid. You can make your own by mixing 1 cup water, 1/2 cup vinegar, 1/4 cup lemon juice, and 1/16 cup salt. Slick

Re; “The active ingredient is citric acid.”
I put some blackest wire core in some Jenolite, knowing it contains citric acid, which brought back the copper colour considering the age of the wire.
Not that I endorse doing this, it would only be a stop / gap method considering that the rest of the wire in the insulation would be black and giving a HUGE electrical resistance ( some drop the voltage by as much as 50% on a 6 volt wiring harness I once worked on.
The only remedy is to replace the offending wire with new-they are cheap :!: )

http://www.amazon.co.uk/Jenolite-JRR045 ... B002SLHLYM

Changing the wire harness because of oxidized wires is a pretty labor intensive solution for a problem that is easily solved by overhauling the harness connections. Just to be clear, the only resistance that you'll get from oxidized wire is on the connections, not in the run of wire. In addition to that good practice of chemically etching the ends, you can also use a good solder flux and tin the ends to remedy a resistive connection.

How do you determine if you have a resistive connection? You can perform a voltage drop test at each connection to find which part of the harness has a resistive connection. Put your volt meter across each connection, with power on. When you show a voltage across a connection, you have a resistive connection. A good connection won't show any voltage, because there is no voltage drop at the connection. Zero volts would be a perfect connection. Acceptable voltage drops would be below 1/2 a volt. On 6 volt bikes, the voltage drop effect is more pronounced than a 12 volt system (in engineering speak: I squared R loss). You also have to do this voltage drop test at load with the bike's electrical system energized.

Good luck, and if you break Ohm's law, you'll have to pay the smoke fine.

Kevin

@ LA Kevin

+ 1

I just fan the strands out and lightly scrape them with a blade or stroke/brush them with a stiff bristle stainless brush.
Should the citric acid be neutralized after its use? That is, some kinds of flux over time result in corrosion.

A friend of mine reckons putting the ends of the wire to be soldered in a small ultrasonic cleaner for a few minutes works, but I haven't tried it myself yet.

Someone suggested tinning the wire ends. If the wire ends are cleaned and tinned, do not attempt to crimp on a terminal, or use a screw to clamp wire. The solder "creeps" under the crimp or screw pressure, and the connection will loosen. It is OK to solder on a terminal directly to the wire. In this case, the solder chemically bonds to both the wire and terminal.

Slick

Interesting Slick, that's a new one for me - the fact that the solder creeps under pressure. Rings true to me, I've seen it but not realized that that was why the connection was poor.

Another thing - OEM auto, bike, marine and aerospace practice is always crimp, never solder.
I assume that's because soldered joints eventually fail from their inability to withstand vibration.

xbacksideslider said:

Interesting Slick, that's a new one for me - the fact that the solder creeps under pressure. Rings true to me, I've seen it but not realized that that was why the connection was poor.

Another thing - OEM auto, bike, marine and aerospace practice is always crimp, never solder.
I assume that's because soldered joints eventually fail from their inability to withstand vibration.

Click to expand...

As you say, crimp connectors are the preferred method. However, it is a myth that soldered joints cannot resist vibration. Failure in soldered connections is caused by relative movement between the wire and the part, or if the vibration causes bending to occur at the soldered joint. For example, components soldered on a printed circuit board subjected to vibration, may have the joints fail because the board is bending at the pin junction....sort of like bending a tab of metal back and forth until it breaks. OTOH, a wire properly soldered to a solder cup terminal is not likely to fail, unless the wire bends back and forth .....this is like the failure of tool cords which we all have experienced.

The bullet connectors on my Atlas have the wire soldered into them....original Norton wiring....50 yrs and 85K miles .... not one failure.

Slick

Whenever I use a zip tie, I throw the clipped off tag end into my box of crimp connectors/solder/shrink tube. I confess that when I splice wires I prefer to solder/shrink tube them but I slip a piece of zip tie under the shrink tube before I heat shrink it so that there is a splint to prevent flexing of the wire on either side of the soldered joint.