Bronze was first created thousands of years ago by mixing copper together with arsenic, and then later, tin. The resulting copper alloy proved itself to be stronger and harder than any other type of metal available and was suitable for use in weaponry, sculpture and architecture. The widespread use of bronzes led to the “Bronze Age” in the third millennium BC. Today, copper alloys that contain metals other than tin also get called “bronzes” and the term “brass” is sometimes used interchangeably with bronze. The most common types of bronzes still used in modern applications are statuary bronze, architectural bronze and commercial bronze.
Bronzes are hard, brittle and gold in colour. They have a high level of ductility, are durable and do not cause high amounts of friction or sparks when struck against other metals or hard surfaces. Bronzes do oxidise, but only superficially, so that the resulting copper oxide layer can serve to protect the metal underneath from further corrosion, depending on the atmospheric conditions to which the bronze is exposed. Further characteristics of bronzes depend very much on the other materials used to create the copper alloy – there are many possibilities suited to different applications.
Production and processing
The base metal for the production of bronzes is copper, which is produced predominantly in Chile, Peru and China. The copper is either smelted, processed with solvent extraction and electro-winning or extracted using in-situ leaching. To produce bronzes, copper is again melted with one or several other materials to form a copper alloy. These include tin, arsenic, silicon aluminum, phosphorous, nickel, manganese and iron.
Today, bronzes are used in architecture and sculpture, for tools and bearings, for electrical contacts, and in musical instruments, coins and ship propellers. Phosphor bronzes are used in masonry and for all manner of fasteners, springs, and gears because of their high resistance to corrosion and excellent strength. The protective patina and pleasant resonance of phosphor bronzes make them perfect for use in bells. Aluminium bronzes are ideal for marine applications. Their attractive golden colour also makes them popular in architecture, along with silicon bronzes that are strong, ductile, corrosion-resistant and suitable for welding.
- Highly corrosion-resistant
- Attractive gold colour
- Good heat and electrical conductivity
- High ductility and durability