Stainless steel alloys actually do corrode in order to work. Ideally the Chrome (alloy content not plating) creates a very thin film of non-corrosive Chromium Oxide that protects the iron; which is the majority of the alloy. Normally that thin layer will "self-heal" when scratched. Even the most expensive grades of stainless, like 316L, can show surface rust or even pitting. The problem occurs when the Chromium Oxide is scratched and/or is unable to repair itself (self-heal). Iron particles are the most common culprit.
Higher Nickel and Chrome content alloys are generally more "rust" resistant. Rust is corrosion of Iron or Iron Oxide. Stainless steel cutlery is magnetic because high Nickel-Chrome alloys are too soft to hold a decent cutting edge. However, if you take care of these knives they rarely show surface rust. The most common alloys found in dive gear are 302/304. They have high enough Nickel and Chrome to be pretty good and have very low magnetic signatures, but are significantly less expensive and a little easier to machine than 316. Optimum manufacturing methods include
passivation (commonly called pickling) after all fabrication processes to dissolve surface Iron and form a uniform Chromium Oxide layer.
Back to your basic problem: There is a good chance you can use a non-metallic abrasive pad like many kitchen sponges have to remove surface rust. This will also remove some of the Chromium Oxide layer but it will usually regenerate on its own. A very common source for this kind of rusting is surface iron transferred during the manufacturing process (steel rollers, drills, punches, etc) and not pickled. There are several DIY passivation processes that you can do that doesn't attack webbing that may be sewn on the part.
I have seen very expensive 316L stainless steel electrical panels on offshore oil production platforms ruined because a welder working nearby sprayed steel sparks all over them with a grinder. The surface rust wasn't noticed until the pitting broke through.
