- The contact pads on carts are made of copper, with an in-between layer of nickel and a top one of gold.
- Gold does NOT rust/oxidize. It will tarnish, but will never oxidize.
- Never use commercial metal polishers such as Brasso or BlueMagic. They will remove the plating.
- Forget about using sanding paper no matter how fine! The gold layer is only a few microns thick, you will remove it quite easily.
- Any other polishing agents such as toothpaste. It may be safe for your mouth, but is not for electronics.
- A very mild solvent to remove oils or mild chemicals, such as isopropyl alcohol 91% (or higher). Alternatively, you can use distilled or deionized water.
- A clean and soft cloth. Microfiber would be preferred. You can use a paper towel but be mindful of the paper leftovers.
- A commercial contact cleaner for electronics such as DeoxIT ProGold Connector Enhancer from CAIG labs. If you can't afford it or just don't want to buy one, you can use a pencil rubber eraser instead to polish the pads.
All you have to do now is to clean the pads in an up and down motion (not sideways) with the cloth and isopropyl or distilled/deionized water, then apply your commercial electronics contact cleaner and wipe it off with a dry part of your cloth. Do not remove the film it leaves behind, is a special lubricant.
If you use the eraser rubber instead, do it in an up and down motion on each contact. Then clean the contacts again at the end with your mild solvent of choice.
Your cart is now squeaky clean and it should work for a very long time before having to clean it again.