Stainless steel is a steel alloy that does not stain, corrode, or rust as easily as ordinary steel due to its content of chromium. Stainless steel must be a minimum of 11% chromium, but the amount can be increased depending on where the metal is needed. In total, there are over 150 grades of stainless steel. Some also contain nickel and molybdenum.

The concept of stainless steel was envisaged during the early 19th century, but it took around 80 years to develop a reliable industrial method. The invention of modern stainless steel was achieved in 1913 by Harry Brearley (1871-1948), an English metallurgist. He originally named his invention "rustless steel" and used it to manufacture cutlery, such as knives, forks and spoons.

In the 21st century, stainless steel is used for many purposes. Stainless steel forms the structure of many buildings and bridges; cookware, such as saucepans; vehicles, including cars, trains, aircraft and spacecraft; kitchen sinks; jewellery; and weapons.

Chromium is a shiny metal that reacts with air to produce a very thin coating of chromium oxide, which prevents it from rusting. It appears on the periodic table with the symbol "Cr" and atomic number 24.

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