What Is Naval Brass?
Naval brass is a type of special brass made by adding a small amount of tin (about 1%) to 64 brass (a copper alloy consisting of 60% copper and 40% zinc). It is also called naval brass because of its high resistance to seawater and is mainly used for ships and in the chemical industry.
Admiralty brass, which is made by adding tin and arsenic to C73 brass, is also known as a special brass with tin added. However, its use in Japan is limited due to its inferior resistance to corrosion compared to aluminum brass (Alblac) to which aluminum is added.
Uses of Naval Brass
Naval brass is used in marine applications due to its high resistance to seawater. Its excellent corrosion resistance also makes it suitable for a wide range of other applications, including bolts, nuts, valve stems, and condenser plates, as well as for chemical and other industrial equipment.
A related copper alloy, made by adding a little less than 1% each of lead and manganese to Naval brass, has excellent punching and fatigue resistance and is called instrument valve brass (JIS: C6711). As the name suggests, this alloy is widely used for instrument valves such as organs.
Characteristics of Naval Brass
Naval brass is characterized by its high corrosion resistance. Ordinary brass is also said to be a relatively corrosion-resistant alloy, but it is known that dezincification, or dezincification corrosion, occurs. This dezincification corrosion is a phenomenon in which the zinc component in the alloy preferentially dissolves, leaving the copper component unbalanced, and thus corrosion is more likely to occur. This is not a problem when the zinc content is low, but since ordinary brass alloys typically contain about 30~40% zinc, this corrosion cannot be ignored and has been said to cause reliability problems under corrosive conditions.
Naval brass has excellent corrosion resistance to both freshwater and seawater. While adding tin increases hardness and strength, it is said to decrease elongation.
Naval brass is particularly resistant to seawater, but in recent years, the use of alloys with higher corrosion resistance has been increasing, such as aluminum brass (Alblac), an alloy made by adding aluminum to brass, and cupronickel, a copper alloy containing nickel. The use of traditional brass is said to be declining.