Stainless steel threaded pipe fittings are not really not rusty
304 stainless steel is American standard names, SUS304 is called in Japan, the Chinese habit of the elements directly call out, so accustomed to the Chinese call: 0Cr18Ni9.
Stainless steel rust is the mechanism of the formation of a dense alloy alloy oxide film, cut off contact with oxygen to prevent the continued oxidation, so stainless steel is not not to rust, but the time to be long to the late.
304 there are several reasons for the rust of the material:
1 the use of chloride ions in the environment.
2 there is no solid melting treatment.
3 material does not contain titanium and niobium have a natural tendency to intergranular corrosion.