You use metal alloys
everyday. You encounter alloys in jewelry, cookware, tools, and most other items made of metal. Examples of alloys include white gold, Sterling silver, brass, bronze, and steel. Here are 10 interesting facts about metal alloys.
- An alloy is a blend of two or more metals. The blend can form a solid solution or it can be a simple mixture, depending on the size of the crystals that form and how homogeneous the alloy is.
- Although sterling silver is an alloy consisting mainly of silver, many alloys with the word "silver" in their name are only silver in color! German silver and Tibetan silver are examples of alloys that don't actually contain any elemental silver.
- Many people believe steel is an alloy of iron and nickel, but actually steel is an alloy consisting primarily of iron, always with some carbon, with any of several metals.
- Stainless steel is an alloy of iron, low levels of carbon, and chromium. The chromium gives the steel resistance to "stain" or iron rust. A thin layer of chromium oxide forms on the surface of stainless steel, protecting it from oxygen, which is what causes rust. However, stainless steel can be stained if you expose it to a corrosive environment, such as seawater. The corrosive environment attacks and removes the protective chromium oxide coating more quickly than it can repair itself, exposing the iron to attack.
- Solder is an alloy that is used to bond metals to each other. Most solder is an alloy of lead and tin. Special solders exist for other applications. For example, silver solder is used in the manufacture of sterling silver jewelry. Fine silver or pure silver is not an alloy and will melt and join to itself.
- Brass is an alloy consisting primarily of copper and zinc. Bronze, on the other hand, is an alloy of copper with another metal, usually tin. Originally, brass and bronze were considered to be distinct alloys, but in modern usage, brass is any copper alloy. You may hear brass cited as a type of bronze or vice versa.
- Pewter is a tin alloy consisting of 85-99% tin with copper, antimony, bismuth, lead, and/or silver. Although lead is used much less commonly in modern pewter, even "lead-free" pewter typically contains a small amount of lead. This is because "lead-free" is defined as containing no more than .05% (500 ppm) lead. This amount remains appreciable if the pewter is used for cookware, dishes, or children's jewelry.
- Electrum is a naturally occurring alloy of gold and silver with small amounts of copper and other metals. The ancient Greeks considered it to be "white gold." It was used as far back as 3000 B.C. for coins, drinking vessels, and ornaments.
- Gold can exist in nature as a pure metal, but most of the gold you encounter is an alloy. The amount of gold in the alloy is expressed in terms of karats. 24 karat gold is pure gold. 14 karat gold is 14/24 parts gold, while 10 karat gold is 10/24 parts gold, or less than half gold. Any of several metals can be used for the remaining portion of the alloy.
- An amalgam is an alloy made by combining mercury with another metal. Almost all metals form amalgams, with the exception of iron. Amalgam is used in dentistry and in gold and silver mining because these metals readily combine with mercury.