Stainless steel is a family of iron-based alloys defined by corrosion resistance, achieved by adding a minimum of 10.5% chromium. Its formal discovery was not a single invention but the culmination of nearly a century of metallurgical research. The breakthrough that produced the first commercially viable version is most accurately dated to 1913, led by a British metallurgist working in Sheffield.
Early Chromium Alloys and Corrosion Resistance
The foundation for stainless steel began in the early 19th century with the realization that chromium could impart corrosion resistance to iron alloys. In 1821, French metallurgist Pierre Berthier noted that iron alloyed with chromium resisted certain acids and suggested its use for cutlery. However, the technology to make it commercially viable did not yet exist. The primary challenge was the high carbon content in available ferrochrome alloys. This excess carbon made the resulting metal extremely brittle, rendering it useless for industrial applications. For decades, scientists knew chromium was the key ingredient but struggled to create a malleable and durable metal.
The 1913 Breakthrough: Defining Stainless Steel
The definitive discovery occurred in Sheffield, England, where metallurgist Harry Brearley was commissioned to solve a military problem. Working at the Brown-Firth research laboratory, he sought an alloy that could resist the erosion caused by heat and friction inside gun barrels. Brearley experimented with steel alloys containing varying amounts of chromium, which was known to raise the metal’s melting point. On August 13, 1913, he created a specific cast containing 12.8% chromium and 0.24% carbon.
He initially discarded this sample because it lacked the desired anti-erosion properties for gun barrels. Months later, Brearley noticed the sample resisted the acid etching process used to reveal metal microstructure. While other alloys rusted immediately, the 12.8% chromium steel remained bright and untarnished, even when exposed to nitric acid. This accidental observation revealed he had created a corrosion-resistant metal: a martensitic stainless steel alloy. This was the first successful, low-carbon iron-chromium alloy resistant to rust and acid attack.
Immediate Industrial Application and Naming
Despite the scientific breakthrough, Brearley initially struggled to convince his employers of the commercial application for his new “rustless steel.” The initial use was not military but domestic, specifically for cutlery prone to staining from food acids. He took the discovery to a local manufacturer, R. F. Mosley, whose manager, Ernest Stuart, quickly recognized the alloy’s potential for non-staining knife blades. Stuart is credited with coining the name “stainless steel,” which quickly replaced Brearley’s original term.
Parallel developments reinforce 1913 as the official starting point. In Germany, Krupp engineers Benno Strauss and Eduard Maurer patented an austenitic stainless steel—a type with higher chromium and nickel content. Simultaneously, American metallurgist Elwood Haynes was also pursuing patents for a martensitic stainless steel. Brearley’s discovery, however, led directly to the first successful industrial production and commercialization of the alloy.