By the late 1920's, two types of stainless steel had been found to be most versatile and useful; modernistic stainless steel (chromium content of 13-18 percent) and acetonic stainless steel (18 percent chromium and 8 percent nickel). Today, stainless steel is a generic term given for a group of corrosion resistant steels containing a minimum of 10.5 percent of chromium, which creates a passive, self renewing film of chromium oxide around the steel at the atomic level, thereby impeding the iron from rusting.
Technical development over the decades has followed two paths: the incremental improvement of the standard grades invented in the 1920s as well as the development of entirely new grades. However, the core attributes of stainless steel i.e. strength, heat and corrosion resistance, strength; form ability, aesthetic appearance and low maintenance have not changed with technical developments. Stainless steel producers still continue to do research into chemical composition, innovations in stainless steel making technologies, new rolling technologies, quality control and lower costs.