These unprotected Stainless Steel 304H Lap Joint Flanges rusts readily when exposed to air and moisture. Since iron oxide has lower density than these Stainless Steel 304H Ring Joint Type Flanges, the film expands and tends to flake and fall away. In comparison, our Stainless Steel 304H Spectacle Blind Flanges contain sufficient chromium to undergo passivation, forming an inert film o... https://www.universemetal.com/stainless-steel-304h-flanges-manufacturers-suppliers-stockists-exporters.html