When plastic appears to have rusted, it is usually a result of rust being in contact with the plastic and staining the surface rather than the plastic oxidising because of iron content. As a result, removing rust from plastic is more about stain removal than actual rust removal. To best remove rust from plastic without damaging the surface, you will need common household cleaning items--and some patience.
Clean the entire piece of plastic thoroughly. Sometimes, what appears to be rust is actually largely dirt or other build-up. You will save yourself a lot of time by making sure that the plastic area is as clean as possible before you start treating the rust stain.
Mix a cleaning paste. Pour enough baking soda over the rust stain so that it is covered completely. Add vinegar a tablespoon at a time while mixing with your gloved fingers until you have created a thick, spreadable paste that will not run. Expect fizzing during this process.
Cover the entire rust stain with the paste. Make sure that it is completely covered with wet paste because dry baking soda alone will have little impact. You can leave the paste in place for 15 minutes. If the rust stain is not on a level surface, you may cover the paste and the stain with a cloth saturated in vinegar to keep the stain covered.
Scrub off the paste using the plastic scrubber. The scrubber will not scratch the plastic surface. Use firm pressure and circular motions. You likely will notice that the stain has lightened but not disappeared completely. Repeat the paste treatment up to four more times to get full removal.
Clean the area. Once you have got rid of the stain, you will need to spray down the area with the spray cleaner and wipe it down again. This will get rid of any baking soda residue and leave your plastic surface clean, smooth and ready to use.
Toothpaste is a popular substitute for the baking soda and vinegar paste.