The corrosion resistance of stainless steel depends on chromium, but because chromium is one of the components of steel, protection methods vary. When the addition of chromium reaches 10.5 percent , the atmospheric corrosion resistance of the steel increases significantly, but when the chromium content is very high, although the corrosion resistance can still be enhanced, it is not very large. The reason is that alloying steel with chromium changes the type of surface oxide to a surface oxide similar to that formed on pure chromium metal. This tightly adhered chromium-rich oxide protects the surface from further oxidation. This oxide layer is so thin that the natural luster of the steel surface can be seen through it, giving stainless steel a unique finish. Moreover, if the surface layer is damaged, the exposed steel surface will react with the atmosphere to repair itself, re-form this "passivation film", and continue to play a protective role.
Zato ima nerjavno jeklo skupno lastnost, to je vsebnost kroma nad 10,5 odstotka.
Izraz nerjavno jeklo se ne nanaša samo na eno vrsto nerjavnega jekla, vsaka vrsta nerjavnega jekla ima dobre lastnosti na svojem posebnem področju uporabe. Ključ do uspeha je najprej razumeti namen in nato izbrati pravo vrsto jekla. Trenutno je običajno le šest razredov jekla, povezanih s področjem uporabe pri gradnji stavb. Vse vsebujejo 17-22 odstotkov kroma, boljši razredi pa vsebujejo tudi nikelj. Dodatek molibdena lahko dodatno izboljša atmosfersko korozijsko odpornost, kot je odpornost na atmosfere, ki vsebujejo klorid.
