Stainless steel - an explanation
Steel is stainless when it is at least 11.5% chromium. However, the stainless part of the name is somewhat misleading when it is used for knives. Corrosion resistant would be more accurate. In fact, all stainless knife steels are a compromise between corrosion resistance and, for better edge retention, hardenability. There is a huge difference in corrosion resistance between austenitic stainless steel (cannot be hardened or heat-treated) and martensitic stainless steel (can be hardened and heat-treated).
For this reason, you should make a habit of cleaning, drying and oiling your knife blades after use. This is especially true if you live in a moist or salty region or are going to store knives in such an environment. To re-sharpen your blades, cold grind them. Use lots of cooling water and always avoid sparks. Sparks are proof of edge overheating. This ruins both the heat treatment and the steel alloy.