Does stainless 304 & 316 that has been highly polished or even matte eventually rust if stored indoors, cleaned regularly with a wet cloth?
If so what time scale? By rust.corrosion I mean visible eye sore.
All the talk about stainless rusting I have read is only about typical usage in coastal areas or in contact with acidic foods.
So far my Stainless has lasted a few years indoors with no signs of corrosion or staining.
Also I read just because it’s grade 316 doesn’t mean much if it’s manufacturing is poor/cheap cost.
316 and 304 should never rust, unless you use steel wool to finish them (which breaks a cycle of self protection by embedding iron particles through the chromium oxide surface layer). Grade 316 means everything, regardless of poor manufacturing or cheap cost. Of course, if somebody is ripping you off by selling you something they claim is 316 but actually isn’t, that’s not 316’s fault.
Note that all stainless needs to be passivated after it has been fabricated, or it will rust where the factory surface is damaged by grinding or welding.
I use something called “citrisurf” to passivated any stainless I’ve welded.
they can still rust, if left in contact with another metal in the presence of an electrolyte; I’ve had dinnerware form red oxide spots if left overnight in the sink touching something else (IIRC most of it’s 304, 18/10) but as you say, decorative pieces kept clean shouldn’t rust on their own.
The concept of passivation is understood, but I’ll note: Our plant shop fabs a tremendous amount of Stainless pipe runs and tank modifications, and this handywork is never passivated. 30 years after the fact, I see such welds/mods look as new as the day they were made… Only occasionally will there be a faint hint of iron staining.
Stainless steel can be forged or cast or drawn. Many household items are cast stainless steel - where iron migrates to the surface during the casting process. The cast material is supposed to be shot blasted and pickled (acid cleaned) before machining for the final object - but manufacturers cut corners. Or they mistakenly use shots that were also used to clean carbon steel, and then the free iron on the surface rusts.
I have also seen corrosion on SS objects when a “wet cloth” is used to clean it - especially if there is high chlorine in the wet cloth (from tap water) or a cleaner that has bleach in it , is used. This corrosion is usually like pits or dimples on the surface. You will commonly see this kind of corrosion on chrome fittings in the bathroom - where bleach or bleach based cleaners are used. I think its a eye sore too - since these dimples are usually green borders on an otherwise highly polished surface.