They are chromed plastic, unfortunately. In order to chrome plastic, it first gets a conductive nickel/copper plating before being electroplated. When the thin chrome layer is damaged, the copper is what gives you the green corrosion. We polished them up occasionally, but they were in better shape than yours.
You can sand it off and paint it white or send off for rechroming, but chromed plastic is just not very good or durable.
Or, apparently, try chrome nail polish:
https://www.youtube.com/watch?v=ninpBuzNSxQ