Plastic trim oxidation/hard water stain?

Hi All!

Does anyone have any idea what this stain is on my plastic running board? I've tried a good washing with car soap and wash mitt, I tried a vinegar wipe down, and then I tried apply some CG VRP to see if that would darken it up a little bit and nothing made any improvement.

Any idea what is and how to get rid of it?

Thanks in advance!


IMG_0303.HEIC - Google Drive

E92ADF60-B80E-4FFF-90A5-07F3A37EA060.JPG - Google Drive

Sorry for the google drive links, the photo upload wasn't working or I just couldn't handle it.

Scrub it with a strong APC or wheel acid and wipe down with IPA and then apply Solution Finish (will darken the plastic).

The black plastic trim on these cars are getting cheaper and cheaper...when it gets stained like that, it's almost always impossible to remove, and attempting to remove it often makes it look worse.