Thats not correct. 304 and 316 are both high chromium nickel stabilised austenitic grades with good corrosion general resistance. All stainless steels rely on the chromium to preferentially oxidise and create an adherent oxide layer that prevents further corrosion beneath it. Either grade could be left outside and wouldn't rust/tarnish in normal conditions.Keith 66":3uj9o15n said:Screws into oak, depends where & what application. Stainless steel screws come in two grades A2 Or in old money 304 grade which is a cheap commercial grade, It will discolour & rust slightly if outside.
A4 or 316 which is marine grade & far more durable. The main problem with stainless for marine applications is it relies on the oxide layer to resist corrosion, in acidic woods like oak for say boat keels etc it can get crevice corrosion & can actually corrode & fail faster than if you had used ordinary steel.