Polishing would be the obvious choice. Plating could be an option too. What kind of appearance are you trying to get? If you are trying to spec this on an engineering drawing it would be an idea to define the surface roughness you require.
Yes to polishing but as Gareth said "what roughness are you concerned with. If roughness is not a consideration, a simple way to polish SS without changing is surface finish is to electropolish. This process electrochemically polishes the surface and will make even things as rough as welds bright and shiny. However for this to work properly the substrate material must be as homogeneous as possible, meaning selection of welding rod and process is critical.
This is a wide open question, what is the material, sheet metal, angle, box sectionetc What grade material? What is the application? What is the shape? SWG? Depth" Anyway, lets assume that it is something that I have experience in! Stainless steel enclosures. Hand polishing. Depending on the shape and guage this is a quick and effective way of polishing the surfaces, but be carefull who you use, differnt polishers have different standards. The soap used to polish the component stays on the surface and is invisible, however there are trace elements of previouslly polished materials left on the mop and these will transfer to the next component. Electropolishing. Again this depends on the application. Basically the process removes all the microscopic high points of the substrate (micro smoothing) and thus you get a shinny surface. The process is quick, relativelly cheap and the finished component will have a chromium rich surface which will oxidise and prevent rusting to a much superior level than hand polishing. The down sides to the process are mainlly that the surface scratches very easilly and if there are any areas for chemicals to bleed into touching surfaces (capillary action) then you will have staining problems at a later date. Any questions please just ask
