Stainless Steel

In metallurgy, stainless steel (inox) is defined as a ferrous alloy with a minimum of 10.5% chromium content. more...

The name originates from the fact that stainless steel stains, corrodes or rusts less easily than ordinary steel. In the United States and world-wide, particularly in the aviation industry, this material is also called corrosion resistant steel when it is not detailed exactly to its alloy type and grade.

Properties

Stainless steels have higher resistance to oxidation (rust) and corrosion in many natural and man made environments, however, it is important to select the correct type and grade of stainless steel for the particular application.

High oxidation resistance in air at ambient temperature is normally achieved with additions of more than 12% (by weight) chromium. The chromium forms a passivation layer of chromium(III) oxide (Cr₂O₃) when exposed to oxygen. The layer is too thin to be visible, meaning the metal stays shiny. It is, however, impervious to water and air, protecting the metal beneath. Also, when the surface is scratched this layer quickly reforms. This phenomenon is called passivation by materials scientists, and is seen in other metals, such as aluminium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect that is known as galling.

Commercial value of stainless steel

Stainless steel's resistance to corrosion and staining, low maintenance, relative inexpense, and familiar luster make it an ideal base material for a host of commercial applications. There are over 150 grades of stainless steel, of which fifteen are most common. The alloy is milled into sheets, plates, bars, wire, and tubing to be used in cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment, and building material in skyscrapers and large buildings. The famous seven-story pinnacle of the Chrysler Building in New York City is adorned with gleaming stainless steel cladding.

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