History of Stainless Steel
Since ancient times, only a few pieces of corrosion‐resistant iron have survived to the present day. The most famous and largest example is the "Iron Pillar of Delhi" in India, commissioned by Kumaragupta I in the 400s. However, unlike stainless steel, this iron monument derives its corrosion resistance not from chromium but from its high phosphorus content.
Under favorable local atmospheric conditions for phosphorus reactivity, a protective surface layer composed of iron oxide and phosphorus forms on the monument. This coating effectively shields the iron from corrosion.
The corrosion resistance of iron–chromium alloys was first recognized in 1821 by the French metallurgist Pierre Berthier. However, the technology of that era did not allow iron to be processed with chromium as we do today, so practical applications could not be realized.
In the 1890s, the German Hans Goldschmidt discovered the aluminothermic method, which paved the way for the production of carbon-free chromium. From that point on, numerous studies on stainless steel were undertaken.
Modern stainless steel began its evolution in 1913 when the British metallurgist Harry Brearly accidentally discovered it while researching improvements for rifle barrels. This serendipitous find marked the origin of stainless steel. Subsequent developments led to the introduction of the austenitic stainless steel, commonly known as 18-8 (or 304), in the 1920s—a grade that achieved great success in its applications. Since the 1930s, stainless steel has become indispensable both in industry and in everyday life.
Researchers building on these early advancements, and incorporating additional alloying elements, have gradually perfected the stainless steel grades known to us today.
Duplex stainless steels were developed approximately 70 years ago for use in the sulfite paper industry. Initially, duplex alloys were employed to address corrosion issues caused by chloride-rich cooling waters and other aggressive chemical process fluids. In the 1970s, with the emergence of gas and oil facilities in the North Sea, a second-generation duplex stainless steel was developed.
With the deliberate addition of nitrogen, these steels achieved enhanced toughness, weldability, and improved resistance to chloride-induced corrosion. The mixed composition most widely used, designated UNS S31803, was standardized as duplex stainless steel UNS S32205 in 1996.
During World War II, research led to the discovery of precipitation-hardened stainless steels. The first example of this non-standard grade emerged in 1948 and was named 17-7PH stainless steel.