First gen plasma corrodes, if you try to remove it you're actually just removing the plasma finish.
That's absolutely correct. Any abrasive such as polishing agents or scouring pads are actually stripping away the coating. There are chemicals that can strip microns of the coating, which is just enough to remove the tarnish or light corrosion but the stuff I use aren't available off the shelf. Oh and be warned... some chemicals actually cause more corrosion!
if you love that sparkling silver, clean crisp G1 plasma without the hassle of corrosion, you're better off refinishing it to one of my permanent G1 finishes... all the bling and never chip nor corrode.