In conditions where moisture and atmospheric conditions are normal, stainless steel does not rust, but when conditions are more extreme, corrosion may occur. Stainless steel is much more resistant to corrosion than regular alloy steels. However this does not mean there are not conditions under which it rusts.
High levels of moisture or salinity can cause stainless steel to rust more readily. Poor air circulation or enclosed areas also cause rust to form. Stainless steel items with engraved designs or pitted areas may trap moisture more easily and cause rust, while items with smooth surfaces are more resistant to corrosion.