I found this a while back, ideal for cleaning up corroded wires before soldering.

Wire Cleaning.

This process uses two solutions, one is regular table salt and vinegar. Any kind of vinegar will work, from balsamic, to rice, to white vinegars. Its the acidity and corrosiveness of the salt and vinegar together that you want. The other solution is Sodium Bicarbonate, or baking soda, and water. This is used to neutralize the corrosive properties of the other solution, and to further clean the wires.

Step 1: Strip the wires to be cleaned.

Step 2: Get 2 containers, one for each solution. They can be paper cups, plastic, glass, bowls, whatever you can find.

Step 3: Get 1 tablespoon of raw salt, and put it in one of the containers. Fill up the rest of the container with vinegar, and stir the both together. As a general rule of thumb, put as much salt in the vinegar as will dissolve.

Step 4: Get 1 tablespoon of Sodium Bicarbonate, (baking soda) and add it to the other container. Fill up the rest with water, and stir well. Add more baking soda to make it cloudy. The amount is not important, as long as it is alkaline to cancel the acid of the vinegar solution.

Step 5: Put the stripped end of the wire in the vinegar solution, and stir the solution with the wire. any wire you want cleaned needs to be under the solution. Movement of the wire in the liquid speeds up the process.

Step 6: After 2 minutes or so, the wire will look very shiny and new in the vinegar solution. The acid and salt in the solution is etching away the oxides, exposing the bare metal. Make sure the metal is uniformly shiny. Leave it in longer if it is not perfectly clean throughout.

Step 7: Once the wire is satisfactorily clean, remove the wire from the vinegar, and plunge it into the baking soda solution to neutralize the acid's corrosive properties. If the wire was exposed to the air, without neutralizing the acid first, it would quickly corrode again. The baking soda keeps it clean and shiny. Swish the wire around in the baking soda water for about 10 seconds, and then you are done!! Shiny new wire ready for soldering, and conducting once again!!

Location: Pembrokeshire

Simon and Phil - thank you both.

After you have cleaned the connections by any method i suggest Duck oil or WD40 will reduce any future oxidisation.

Coke or Pepsi are just as good.

OH NO! WD40 leaves an insulating film after drying. On a ship, one of my maintainers found out the hard way after spraying the very many relays and switches in several of the communications controle boxes around the ship on open decks. Instant problems! Took a very long time cleaning off each individual contact in all boxes to get it all working properly again.

Location: NW Devon

Once connections/switches cleaned (and after soldering wire) use a Contact Treatment Grease. For example RS components do a 20g syringe container. It may seem a bit expensive but you only smeer a very thin coating on contacts to help prevent corrosion, spark burning and lubricate the contacts. Makes switch action smoother. Also use on battery terminals.
I have had mine for years and still not even used 1/4 of the tube.

Location: NW Devon

We've just used this with great success this morning on our Transit van - half an hour before MOT and the entire instrument panel was dead. Pulled out the pod, found everything behind the dash was pretty sh***y, squirted the plugs and sockets and fuse holders and we were back in business!

Does what it says on the tin!

Location: Herefordshire, with an "E" not a "T".

Location: Shropshire

Ian's cleaner and Derek's protector arrived today and everything is working properly again - many thanks again!