Originally Posted by
Duragrouch
Huh, good to know. I knew there were architectural exterior steels that rusted to a certain point and then stopped, at least according to dad; Commercial buildings like that were very much in vogue in the '70s, zero exterior maintenance.
My folder frame and fork is 4130, probably not terribly thick, so the few small spots of rust it had when I got it, I Osphoed and touched up with reasonably matching fingernail polish.
Architectural steels are known as "weathering grade" HSLA steels that form a surface rust protective patina. Most fall under ASTM A242, A588 and others. These steels are used for numerous applications with outdoor exposure.
Consumer grade stainless like 304 or 316 have a minimum chrome content of 18%, hence they are known as 18-8 SS. 400 series has less chrome and corrosion resistance. Choosing between m
artensitic stainless steels and austenitic types really matters on the application being used in and the characteristics required.
Working in underground infrastructure construction all our fasteners were 304, 316, Corten, or A242 steels