You do not polish chrome, you clean it. Unlike aluminium and stainless steel, chrome does not oxidize much. Without cleaning it especially after shower or washing there will be watermark for sure. Once Its leave without cleaning it there will be thickened due to soap scum and many other chemical sits other chemical on it. It is extremely and usually very thin (a few mils) plated. People have tried may types of polishes, including expensive ones, and have found nothing that will remove scratches from chrome. Once scratched, you live it re-chrome it.
CHROME PLATING PROCESS
- Copper underlay - a filter
- Nickel - for the mirror colour
- Hard chrome - outer surface