How Is Stainless Steel Different from Carbon Steel?

Carbon steel contains at least 95%iron with up to 2% carbon. The higher the carbon  content, the stronger the steel. Stainless steel also contains iron, but in addition it must contain at least 10.5% chromium and the carbon content is very low, usually 0.08% maximum. Stainless steel gets it strength from the metallurgical structure,rather than from the amount of  carbon present. Carbon steel can be strengthened by heat treatment whereas the 300 series stainless steels cannot.

Stainless steel can be strengthened by work- hardening the structure.The 300 series stainless steel grades (304 and 316) contain nickel from 8 to 14% in addition to the chromium that must be present. 316 contains an additional element, molybdenum, from 2 to 3%. It is these alloying elements added to the iron base that makes stainless steel very different from carbon steel.

Reference: http://www.nemaenclosures.com/blog/wp-content/uploads/2012/09/stainless-steel-corrosion.pdf