Clean & polish stainless steel..?

[miseryguts]

They are air vents embedded in a wall.. I've removed the face plates & almost removed god knows how many layers of paint.
They are what I can only describe as speckled with black marks which no amount of sandpaper/elbow grease etc has yet made a difference to, I can't replace them as they are non-standard size & design.. and I really don't want to paint them.

Anyone any ideas how I could remove these marks & if I can what is the best way to polish them?

Thanks.

 

[JohnKay]

They sound more like galvanised, rather than stainless. I would have used a chemical paint stripper, and finish off with a Scotchbright pad.

As these are now obviously scratched, it can't do much more harm to try with a fine wet/dry abrasive (the car body stuff) but if galvanised, you will be removing the zinc plating.

You could end up painting after all !

 

[Essex]

And if galvanised and down to the galvanized finish, you will need to use self etching primer before adding a top coat