Bronze is a metal alloy. Bronze is mostly copper, with some tin added (usually between 5% and 20% tin) to make it stronger. The most common alloy is just made of copper and tin. Some bronzes add other metals.
Other bronzes are:
- Aluminum bronze, which uses aluminum instead of tin.
- Leaded bronze
- Silicon bronze
- Phosphor bronze, which has both tin and phosphorus added to the copper.
Bronze should not be confused with brass which is a different alloy of copper and zinc.
Bronze was the first alloy that was used by humans. The first nation that used bronze was Egypt about 3500 years B.C. This gave the name for the Bronze Age.
Bronze is stronger than copper or tin alone. Bronze lasts longer than copper. Pure copper can be oxidized by air and also by water. When copper is oxidized by air or water, it turns green (the color of "copper oxide"), and falls apart.
When people learned how to make and work iron, the Bronze Age ended, and the Iron Age started. Iron can be made harder than bronze, but is susceptible to corrosion (see rust). Iron also wears away faster than bronze, when different pieces are moving against each other. Iron is very common, and easy to make. For this reason, iron costs less than bronze. This is the reason why iron is now used where bronze used to be used.
Bronze is still used to make many parts of machines. We use bronze when the part must last for a long time around water and air, or must not wear away. The main things that are made out of it are pump parts, bearings, bells, electrical components, gears, valves, and other things.
Bronze parts are usually cast in a foundry. After they are cast, bronze parts can also be worked in a lathe or milling machine, or drilled. Bronze is not normally worked with a hammer as iron is.
Part of a bronze portrait of Marcus Aurelius