Chromium — Most important element of stainless steel. An addition of 10% chromium will form an oxide film (passive surface film) which renders the steel corrosion resistant. Chromium also increases resistance to scaling.
Nickel — Second most important element. It increases ductility, corrosion resistance, scaling resistance, and high-temperature strength.
Silicon — Primarily increases resistance to scaling.
Manganese — Improves hot-working properties.
Molybdenum — Increases corrosion and high-temperature strength.