How remove oxydation from spades?

Lemon juice.

I can't vouch for the other remedies,but I 2nd the ProGold solution. If the oxidation is bad,use the DeOxit first,then the ProGold. The benefit to this is the fact that the ProGold will actually treat the metal and prevent it from reoxidizing. Check out their website at www.caig.com

A solvent based cleaner just isn't going to cut through that. Use a mild abrasive; toothpaste or an ink eraser will work, but be careful not to remove any plating materials from the spades. Absolutely use a good non-oil based contact cleaner to follow up (not Progold). Crocus cloth is a favorite for oxidized spades, AC plug prongs, etc. It only looks like fine sandpaper, but is much finer than even #1000; available at better hardware stores.

My favorite tool is called the Rush-Eraser. It looks like an aluminum pencil with a knurled knob sticking out one end. Turning the knob feeds micro fine fiberglass bristles out the end where they can be put to work scrubbing everything from tube pins and circuit boards to electrical plugs and spades.

It is possible to remove too much with any abrasive method, but as Bob points out, micro fine abrasives do a great job without leaving contaminates behind.

The Rush-Eraser is manufactured in Syracuse, New York by the Rush Company. I have been using their products on stereo connections for more than fifteen years with excellent results.

I second Albert's recommendation. I've used this product on both audio and medical equipment and it works wonderfully.

will