Copper is one of the most useful metals known to man, and it was one of the first to be utilized. Copper by itself is relatively soft compared with common structural metals. Trace elements are often added to copper to increase the strength, hardness and corrosion resistance. When zinc is added to copper to form brass it is stronger and harder than either of the pure metals and extremely useful for many perforated metal applications.
Zinc is added to copper in amounts ranging from about 5 to 45%. As a general rule, corrosion resistance decreases as zinc content increases. The main problems with the higher zinc alloys, with more than 20% zinc, is dezincification which can occur in a wide variety of acid, neutral and alkaline media. Zinc is a highly reactive metal as it has a very weak atomic bond relative to other metals. Simply, zinc atoms are easily given up to solutions with certain aggressive characteristics. During dezincification, the more active zinc is selectively removed from the brass, leaving behind a weak deposit of the porous, more noble copper-rich metal.
Brass with a higher zinc content has a yellow color while brass with a higher copper content has a reddish color. Therefore the higher the copper content, the more the color of brass changes towards a reddish brown color.
To avoid the dezincification problem, Ferguson uses types of brass with a high copper content such as 80% and 90%.