A key part of any arcade game restoration are the metal parts that make up the cabinet. Often when you begin restoration on an arcade game the parts will be rusted, or the original coating difficult to remove.
This instructable will detail a safe way to remove - and even reverse - rust and paint on metal objects.
For this demonstration I've got two pieces: a coin door from a Donkey Kong upright cabinet, and the inside panel from a Centipede Mini upright cabinet.
Step 1: Gather Your Materials
You need a source of DC power. Some people who like to use this method use a car battery charger because it can handle a heavy load. I don't have one of those, so I use a standard Peter Chou power supply.
You also need a container large enough to hold your piece. If you can't completely submerge it, that's okay, you can always flip your piece around from time to time. You must note though that only surfaces that are submerged in the electrolyte solution will have any reaction.
You need an electrolyte. Most people like to use sodium carbonate (washing soda). Not to be confused with sodium BIcarbonate (baking soda). Available in most supermarkets in the laundry aisle. I didn't have any, and couldn't find it right away, so I used lye. If you DO use lye, be very cautious! It's caustic and will burn you. Once it's diluted in water it's less of an issue, but take precautions!
Lengths of wire to hook up to your power supply. If you use a car battery charger this isn't necessary, as it's included in the unit. I used a couple old lamp cords. One I left the plug on (for obvious reasons) the other I bared the ends. At first I was using alligator clips to clip onto the pieces, but they started degrading quickly because I had them in the solution. I started using clothespins after that.
A sacrificial piece of steel. Could be just about anything. Right now my piece of choice is the hood to an old florescent lamp. DO NOT USE STAINLESS STEEL. It contains chromium, which is toxic, and will leach into the solution as the piece degrades. For smaller pieces I've used a nail.
Step 2: Preparation
Prepare your electrolyte. With sodium carbonate, I've read a mixture of one tablespoon per gallon of water is appropriate. I use slightly less with the lye.
Attach your electrodes. This next part is very important! You must connect the NEGATIVE (cathode) lead to the part you're restoring, and the POSITIVE (anode) lead to your sacrificial piece. Try to keep the electrodes out of the solution as they will begin to break down.
Step 3: Wait!
You should start to see bubbles almost immediately. This is the water breaking down into it's bare components: hydrogen and oxygen. It's best to do this in a well ventilated area as HYDROGEN IS EXTREMELY FLAMMABLE!
Step 4: Check the Piece.
After a while (say an hour) remove the piece. You will probably note that the coating is starting to bubble off (if this is a piece that's coated/painted). You can either take a wire wheel to it, or perhaps some steel wool. It may require multiple treatments to remove all the coating/rust.
Step 5: Pictures of the Finished Pieces
Unfortunately I didn't snap any shots of the Centipede piece before painting, and the Donkey Kong door is still a work-in-progress. Here's a picture of the painted Centipede piece. I used semi-gloss black as I thought it was the closest match.
The coin counter on the unit is something I also used this process on. No pictures of it, but is was basically a big sheet of rust. I painted it with aluminum color paint, it looks brand new.
(pictures to be uploaded later)
Step 6: Things to Note
Some things to remember about this process:
The electrolyte doesn't wear out, no matter how it looks. The water does get broken down, and will have to be added back. Though you may want to make new electrolyte just because it looks /disgusting/. Washing soda is very inexpensive.
Though this process can reverse certain kinds of rust, it can't fill in pits in the surface. If you're going to paint, fill those pits in first.
You don't want to have anode to cathode contact, that's bad. It causes a short. Make sure the two don't touch.