HISTORY OF STAINLESS STEEL

Stainless steel emerged at the beginning of the 20th century as a response to a technical need long pursued by internationally renowned metallurgists and chemists, especially in the United States, Germany, and France. After decades of research, the objective was clear: to develop an alloy that, without abandoning the mechanical properties of conventional steel—toughness, malleability, and ductility—offered intrinsic resistance to oxidation. That is, it could "survive" contact with water, rain, and common corrosive agents without deteriorating like ordinary steel. 

Although the elemental combination of iron (Fe) and chromium (Cr) was already known before the 20th century, the history of stainless steel is intimately linked to the discovery and isolation of metallic chromium. As often happens with many elements, once a metal is isolated, a practical application is immediately sought. Pure chromium, however, was too hard, brittle, and rigid to be used directly, although it was known to possess extraordinary corrosion resistance thanks to its ability to form a superficial layer of chromium oxide (Cr₂O₃). Unlike iron oxide (Fe₂O₃), this layer remains adhered to the metal, protecting it passively and durably. 

Based on this property, numerous researchers tried to create an iron-chromium alloy that combined the mechanical strength of iron with the anticorrosive protection of chromium. There are records of Fe-Cr alloys from the mid-19th century, obtained by reducing chromium oxides in the presence of coke or charcoal. In these processes, molten iron absorbed metallic chromium, releasing oxygen that reacted with carbon to form carbon monoxide (CO) and carbon dioxide (CO₂), resulting in a corrosion-resistant but extremely brittle alloy, capable of pulverizing with a slight blow. In the context of 1890, such materials were impracticable.

The main obstacle lay in impurities: carbon (C), phosphorus (P), and sulfur (S) contents reached up to 3–5% by mass, generating carbides, phosphates, and sulfides that weakened the internal structure of the steel. Even today, electrolytic chromium of maximum commercial purity (99.999%) remains brittle, which gives an idea of the difficulty of working with this metal in its early stages. At that time, apart from noble metals, bronze remained the most viable alloy for demanding applications. It wasn't until well into the 1930s that industrial-quality steel was successfully produced, as evidenced by the case of the Titanic, whose fragility is analyzed in depth in the article dedicated to manganese.

The German Hans Goldschmidt, inventor of the aluminothermic reduction process known as "thermite," achieved a purer Fe-Cr alloy at the beginning of the 20th century, though still too brittle for practical applications. It was the Frenchman Léon Guillet who, between 1910 and 1911, managed to develop the first truly usable stainless steel, building on Goldschmidt's advances. Although he was not the first to combine iron and chromium, he was the first to obtain a tough and malleable alloy, suitable for industrial and domestic use.