Restore Mattel Sizzlers damaged by battery discharge corrosion/tarnish

Years ago, Mattel made little toy cars that had rechargeable batteries in them called Sizzlers. I have recently discovered mine, and would like to refurbish them. As the years have passed the batteries have discharged, corroding the contacts, etc within the chassis. After disassembly of the toy, and removal of the battery, there is green/blue corrosion on the metal pieces needed to complete the electrical circuit to run the car.

Is there a chemical process that a hobbyist can make that, for lack of better wording, I could put these plastic chassis in the solution, and the solution would remove the corrosion/tarnish left behind? Also, am I correct that once the battery has been removed, the corrosion will get no worse?!

Any replies would be greatly appreciated, and thank you in advance!

You can useTarn-X [linked by editor to product info at Amazon] to remove the corrosion. I have rebuilt thousands of Sizzlers over the years, and this is the quickest and easiest way to remove the tarnish and corrosion without damaging the chassis. Many times you will have to leave it in the solution for more than the recommended 5 minutes. I have left chassis in the solution for up to 30 minutes.

**Remove ALL components from the chassis (motor and wheels) before dipping. Otherwise they will be ruined.