Comment Re:how mush pressure does it take accounting (Score 2) 304
the very best stainless never rusts and is non magnetic and expensive.
Of course it never rusts. Rust is the formation of Iron Oxide. That last word is key, "oxide". Quality stainless steel (as with aluminium and titanium) do not rust, but they most definitely do oxidise, they are just more resistant to it than iron.
See the key part of stainless is that the alloys form a protective coating on it which prevents oxidation. When scratched the coating slowly reforms. However there are many cases where this coating can be continuously damaged and oxidation will occur. It doesn't look like "rust" but it definitely is the same mechanism. Tightening stainless on stainless is a classic case which is also why stainless bolts are very sensitive to galling if you don't use a protective grease when you put them together.
There's no such thing as "crap" stainless steel, and expensive does not automatically mean "good" either. Stainless steel comes in many forms and grades which have different purposes and are used for different things. "Austentitic stainless sucks" is 100% false for many applications, but 100% for others. Your pot is likely 304SS, most good pots are. It's far from the most expensive stainless steel but it's great for cooking applications.