Why Stainless Steel Jewelry Is Stainless
Iron, the primary metal in all forms of steel, rusts readily. Stainless steel, an alloy of iron, carbon, chromium, and traces of other metals, is highly resistant to rust or corrosion. A phenomenon known as passivation makes the steel less reactive with its environment, preventing the oxidation reaction that occurs in iron. The chromium in the alloy forms a thin, invisible film of chromium oxide on the surface of the metal that protects iron oxide, or rust, from forming. This passive film also prevents staining and discoloration of the metal under normal circumstances. Few chemicals can etch or corrode the metal, and stainless steel jewelry will not encounter most of these. However, an atmosphere that lacks sufficient oxygen can prevent the chromium oxide film from forming and passivation from occurring in certain types of stainless steel. This property is why not all stainless steel is suitable for body jewelry as piercings may preclude the formation of the oxide film that protects the metal from rusting.
Types of Stainless Steel Jewelry
Manufacturers produce more than 150 types of stainless steel, all of which serve different industrial purposes ranging from decorative cladding on a building's roof to joint replacement implants. All forms of stainless steel contain some amount of chromium to give it its stainless properties. Nickel is also a constituent in all stainless steel, but the metal is present in smaller amounts in jewelry. Almost all stainless steel jewelry is made from one group of alloys known as 316L steel. This alloy contains little carbon, relatively high chromium levels, and a small amount of nickel. Some jewelry manufacturers use 316LVM, a metal produced in a vacuum for a smoother surface. An associated variety known as 317L has similar properties to 316L steels.
302L
An industrial grade of stainless steel with a relatively high nickel content, this alloy should not be used for piercings but can be worn externally.
304L
The alloy used on the Gateway Arch in St. Louis, this steel is durable but unsuitable for body jewelry.
316L, 316LVM
Sometimes called surgical steel, this group of stainless steels are most widely used for jewelry and may be worn for piercings.
317L
A closely related alloy to 316L, this metal has a slightly higher nickel content.
