tbone4343:
Everclear aka 98% pure grain alcohol, check your local liquor store
, as for copper wire corrosion the only way I know to prevent it completely is to make the joint totally air tight. How ever you can keep it to a minimum by cleaning the wire before you tin it, use only enough solder to tin the exposed portion of wire, clean the wire and the joint again, attach the wire to whatever you are soldering it to making sure you have a good mechanical connection, clean the joint/wire again, clip off the end (about 1/4 inch) of the solder (this opens up end of the solder so the flux flows freely), clean the solder, clean and tin the hot (600 degrees) soldering iron, apply the iron to one side of the joint and then solder to the other "(the iron will heat the entire joint before the solder melts), use only enough solder to make a good connection, remove the solder then the iron, clean the joint again and wipe off any residue. Apply the sealer of your choice (heatshrink, conformal coating, etc),
If this sounds like a lot of work just to solder a wire on, your right! But this is the process used on any solder joint that goes into space. Do I use this process everytime on my own stuff, no. But I do use most of it and I've never had a corrosion problem due to a dirty solder joint. Acid corrosion, now that's another story.
CurtD:
Oops, I forgot about silver solder. This is by far the strongest type of joint. You are very correct, use this where the need for strength is king.