Stainless steel is easier to maintain and doesn’t require a protective coating, but is typically more expensive that its carbon alternative.  To be considered stainless steel, 10.5 percent chromium (or more) must be present in the steel.  Adding chromium to the mix creates steel which is highly resistant to rust and corrosion.  Many other alloys may be present as well, each producing a particular grade of stainless steel created for specific purposes.  While more than 50 types of stainless steel are available today, professional-grade railing systems typically use 304 or 316 grades.