Stainless steel

Stainless steel is a family of iron-based alloys containing enough chromium to resist corrosion. Its grades vary in composition and structure, giving them different strengths, formability, and resistance to heat and chemicals.

Passivation: Passivation is the formation of a thin surface layer that reduces a material’s chemical reactivity. Chromium forms a protective oxide layer on stainless steel that can repair itself when exposed to oxygen.
Iron–chromium alloy: An iron–chromium alloy is a metallic material made primarily from iron and chromium. Stainless steel’s defining alloy system begins with iron and enough chromium to resist corrosion.
Carbon steel: Carbon steel is steel whose properties depend chiefly on carbon content rather than substantial alloy additions. Unlike stainless steel, ordinary carbon steel lacks enough chromium to form a durable corrosion-resistant film.
AISI 304 stainless steel: AISI 304 is a widely used austenitic stainless steel containing chromium and nickel. Its general corrosion resistance and formability suit food equipment, cookware, and architectural uses.
Chromium oxide: Chromium oxide is a compound of chromium and oxygen, including the stable oxide Cr₂O₃. A chromium-rich oxide film provides stainless steel’s main barrier against corrosion.
Austenite: Austenite is a face-centered cubic form of iron stabilized at room temperature in some steel alloys. Nickel and other alloying elements help make many stainless steels austenitic and formable.
Weathering steel: Weathering steel is a low-alloy steel designed to develop a protective rust-like patina under suitable exposure. It tolerates controlled surface rust rather than relying on stainless steel’s chromium-rich passive film.
AISI 316 stainless steel: AISI 316 is an austenitic stainless steel containing chromium, nickel, and molybdenum. Molybdenum makes it more resistant than 304 to many chloride-containing environments.
Pitting corrosion: Pitting corrosion is localized attack that creates small cavities in a metal surface. Chlorides can break through stainless steel’s passive film and start deep, difficult-to-detect pits.
Ferrite (iron): Ferrite is a body-centered cubic form of iron with limited carbon solubility. Ferritic stainless grades use this crystal structure and generally contain little or no nickel.

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