Passivate sort of confusing thing. SS picks up iron molecules real easy in molten condition, and also changes color when welded. You get iron in the pool sometimes like from using steel brush on SS welds. Dat steel turns up as rust downline. Same can happen drilling SS with steel drill or even grinding wid same wheel you used on iron.
You passivate proper right after welds cool and welding gods are on yer side, discoloring and often rust potential goes away.
Fellow on another board built expensive SS deck rail system for customer, SS posts & cable. Didn't think what he was doin and drilled wid hispeed steel bit. Few months later customer is pissed about rust forming at every hole where cable passes thru. Problem created by fail to think. Might have not happened he ask before he moved, but he didn't ask. He young guy, talented good hands but short on knowing. Really he drywall guy tryin to be welder. Got young guy disease, jump before looking. Now he either redo or loose future work. People do lot of talking bout bad job, either way big hole in his pocket. Real hard to have experience when you just startin out. Happens to young guys cause dey conditioned to not listen.
Old guys, not to be confused wid men who did same job over & over for 40 years, seen a lot and got lot stored between ears. Old guy tells kid and right quick kid all cranked up yelling things like condescending and know it all or kid yelling "I got degree". OK, learn expensive way. Maybe you sit back after work and think how dat professor only told you what he wanted to tell. Generally professor fellow only got 1 way, and he only know dat from a book. Old fart knows de job generally got at least 3 ways and dey all work cause he learned dem, not read somebody idea what he thought he saw. (removed) is just old guy {cinch up seatbelt} veritable cornucopia of useless and quasi useless information till you need it. (removed) also looked up plenty words in Dictionary and remembered. Called Socratic learning in polite circles. (removed) even knows why Lloyd spelled dat way, old English language not have capitol letters so dey doubled up instead, works wid ffloyd too.