You can get polished stainless steel, water, foam, powder and CO2 extinguishers however almost all wet chemical extinguishers have stainless steel bodies with chromed brass fittings. then they paint them red and do not provide a polished version WHY is there a technical reason or is it supply and demand?

I don't think there are many stainless steel constructed wet chem units anymore. Everyone seems to have moved to mild steel painted.

I checked on a number of UK manufactured wet chemicals and they were made of stainless steel but they still paint them. From another forum they suggested supply and demand as not many WC are produced and going to the addition expense of polishing these extinguisher is not worth it that especially considering the competition from china who most probably do not use SS.