Brass, bronze, pewter, and the various types of steel are all common alloys. Alloys differ from pure metals, such as gold, silver and aluminum, because they are mixtures of two or more metals.
Alloys are formed by mixing two or more molten metals and allowing the mixture to solidify. They are generally developed by starting with one primary metal and adding small amounts of other metals in order to enhance desirable properties of the original metal.
For instance, carbon steel is iron alloyed with a small amount of carbon. Because carbon steel is stronger and less brittle than pure iron, it is more useful in industrial applications. Similarly, stainless steel is an alloy of iron with chromium. Stainless steel is highly resistant to corrosion and is commonly used in the food and chemical industries.
Two more common alloys with a different application are the silver and gold alloys used in most jewelry. Both alloys contain varying proportions of copper. The gold content of gold alloys is indicated by carats, with 24-carat gold being pure gold and lower carat numbers indicating higher proportions of copper. These alloys are both cheaper and stronger than the pure metals, making the jewelry more affordable and more durable without significantly changing the appearance.