Stainless

Stainless refers to stainless steel, a family of iron-based alloys that resist corrosion due to a chromium-rich passive film that forms on their surface. Chromium content is typically at least 10.5%, and the protective oxide layer can reform after being damaged. Alloying elements such as nickel, molybdenum, vanadium, and titanium are added to enhance strength, formability, and specific corrosion-resistance properties. Stainless steels are categorized by their crystal structure into austenitic, ferritic, martensitic, duplex, and precipitation-hardening grades.

The first practical stainless steel was developed in the early 20th century, with Harry Brearley often credited for its discovery in 1913. Its corrosion resistance and versatility led to rapid adoption across industries, from consumer products to industrial equipment.

Common grades include the austenitic 304 and 316 series, where 304 typically contains about 18% chromium and 8% nickel, and 316 adds molybdenum for improved resistance to chlorides and high temperatures. The 400 series comprises ferritic and martensitic grades, offering higher hardness but generally lower corrosion resistance. Duplex stainless steels, such as 2205, combine austenitic and ferritic phases for greater strength and excellent pitting resistance. Precipitation-hardening grades, such as 17-4 PH, achieve high strength through aging treatments.

Applications span kitchenware, medical devices, architecture, chemical processing, and oil and gas. Strengths include corrosion resistance, strength, and adaptability to fabrication processes; limitations involve higher cost, potential susceptibility to localized corrosion in aggressive environments, and specialized welding and heat-treatment requirements. Proper grade selection and adherence to fabrication guidelines are essential for maximizing performance and longevity.