Naval brass is renowned for its high strength, toughness, and corrosion resistance – attributes that make it suitable for harsh conditions. Components constantly exposed to salt air and water (like propeller shafts), plus industrial heat (like welding rods), are frequently made of this alloy.
How did naval brass come to be this strong?
The alloy owes its strength to a makeup of copper and zinc, the traditional combination for brass, plus an all-important fraction of tin. The small percentage of tin – usually no more than 1% — makes brass resistant to dezincification.
Dezincification is a type of corrosion that eats away at the zinc in an alloy until it is completely gone. The item might maintain its original shape and dimensions, but dezincification leaves its structure porous and weak. This problem tends to occur in conditions where alloys come in contact with slightly acidic or alkaline water; in liquid with low flow rates; in water with little aeration; or if alloys are in tube walls with high temperatures.
Brass components aboard ships used to suffer this problem. The loss of zinc manifested as dull red spots on brass surfaces, as well as seepages, leaks, and actual breakage. These problems led to the development of brass formulations with tin – an element renowned for resisting corrosion due to water, and for serving as protective coating for many other metals. The reformulated product came to be known as naval brass.
Aside from incorporating tin, naval brass also resists dezincification through one other configuration: It is never made up of more than 15% zinc.