Copper alloys pipes contain copper as their principal component. They have high resistance to corrosion. As it is high resistant to corrosion, it is used in areas which have high risk of corrosion. Due to its high electric conductivity, pure electrolytic copper is used mostly for making of electrical cables. The similarity in external appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing the different compositions. There are as many as 400 different copper and copper-alloy compositions loosely grouped into the categories: copper, high copper alloy, brasses, bronzes, copper nickels, copper-nickel-zinc, nickel silver, leaded copper, and special alloys.