Cleaning rust off of stainless steel sounds like an oxymoron, but it does need to happen on occasion. Chromium which is what helps the stainless steel from rusting must be present at a level of 10.5% or greater. This element reacts with the oxygen in the air, but instead of making iron oxide, or rust, it forms a chrome oxide which forms an invisible layer which protects your steel from the elements. There are different amounts of chromium in the steel and they can be told apart by their respective numbers 304 and 316.
To clean rust from stainless steel you can use an acidic solution. Most of the time minor surface rust can only form on stainless steel and can’t embed itself further to create the flaky reddish rust we’re used to. A solution of nitric acid or hydrochloric acid can be applied to the area to remove the rust stain. Scrub it with a steel wool brush, or a brush with metal bristles. To prevent the rust from forming on your stainless steel in the future make sure to add a couple of sprays of WD40 and rub it in with a rag.
It’s common to think that if your stainless steel is magnetic, it is less likely to rust. This tends to be true to a certain extent. If your steel is magnetic it has a higher rate of chromium. The 300 series stainless steels are made of knuckle, and are not magnetic. Their cousins in the 400 series are made of chromium is highly magnetic.
When stainless steel reaches a level of 10.5% chromium, chrome oxide instantly starts to form and prevent rust. The steel can be remelted, and reused almost all of the time. That is if there are no defects in the chrome layer causing it to rust. The rusting of stainless steel is fairly rare, happening in less than 1% of steel manufactured.