Brasses

The most important and common group of copper alloys is formed by brasses, which are mainly alloys of copper and zinc. In addition other alloying elements are used.

Brasses are classified as:

Unalloyed brasses
Lead brasses
Special brasses

The golden metal
Brass is an alloy that contains mainly copper (Cu) and zinc (Zn). Its colour that resembles gold makes it unique. Varying the concentrations of copper and zinc and adding other alloying elements gives properties that make brasses useful materials for many different kinds of applications.

Strength and durability will be improved by alloying with iron  (Fe) or aluminum (Al), while corrosion properties are improved by adding aluminum and arsenic (As). The most common alloying element is lead (Pb), which improves machinability of the brasses despite any other alloying elements.

Machinability
By far the largest amount of all produced brasses are used to applications where machinability is required. By adding small amounts of a soft substance which spreads into the structure as small chip breaking particles can improve machinability a great deal. The most common alloying element is lead which by its short chips and smearing properties is transcedent. 

Easyness of surface treatment 
Although brass has a beautiful colour, it is often desired that the surface could be altered or protected somehow. Most copper alloys can be coated with metals in different ways. Nickel and chromium coatings are common in bathroom fixtures.