Brass is among the few metals that are easy to work and mix with other metals. Made by combining copper and zinc, it is essentially an alloy, but other metals can still be added to the mixture to form variations of it. Each brass variant possesses unique qualities that are needed for highly specific applications.
One variant of brass that has gained popularity over the years that it’s been widely utilized for marine applications is the naval brass. This alloy consists of around 60% copper, 39.2% zinc, 0.75% tin, and a trace amount of lead. Such a combination results in a super-brass, with properties not found in other variants.
The Inclusion of Tin
Tin is a soft, silvery-white metal that doesn’t easily oxidize or corrode. The natural oxide film on its surface allows it to resist corrosion from both seawater and tap water. Like other metals, however, tin is not invulnerable to strong acids, alkalis, and acid salts. But since it is highly resistant to corrosion, it is widely used as plating or coating for food containers or anything that requires exposure to oxygen-containing substances.
Just adding 1% of tin to the alloy can significantly increase the corrosion resistance of brass. It should be noted, however, that brass in itself is already corrosion resistant because the copper it contains is also corrosion resistant. Tin, therefore, functions as an enhancer. This way, brass can perform better in extremely corrosive environments.
The Inclusion of Lead
Lead is a one of the densest elements in the periodic table. This heavy metal is soft and malleable, and has a relatively low melting point. These mechanical properties make lead highly workable, and those properties are easily transferred to any metal it is alloyed with. Just a trace amount of lead can have a tremendous effect on the overall quality of an alloy.
Brass, for instance, is naturally workable. However, there are certain applications in which its workability isn’t enough to achieve the needed shape and feature. Lead is added to the mixture to make brass easier to machine. Such an effect can better be explained by the classification of brasses based on their crystal structure.
Brass Classifications
If you look at brass through an electron microscope, you’ll see copper and zinc molecules arranged in a certain pattern. This pattern may not always be uniform across the entire block of brass. Sometimes, there are areas with more zinc or copper, which create defects. There are also instances where the arrangement is symmetrical yet not the ideal lattice structure for brass. As a result of this differences in crystal structure, some brasses become more workable than others.
This is why it is important to classify brasses by their crystal structure. Those brasses with more uniform crystal structure and higher density are classified as alpha brasses. Those that are harder and less workable are called alpha-beta brass. Depending on their degree of workability, they may need to be hot-worked. The types that are hardest to work, and always need to be hot-worked, are classified as beta brass.
Naval brass belongs to the alpha-beta brass family. Since it contains lead, however, it is more workable and machinable than most alpha-beta brasses. It’s no wonder naval brass is preferred for various marine applications, as it can easily be formed into complex ship parts. As an additional perk, naval brass is highly resistant to saltwater corrosion.
If you are looking to use naval brass in your future projects, you might want to consider going to a reputable supplier like Rotax Metals. You will definitely find not just that naval brass piece that you need, but a material that has a better quality than those offered by other suppliers in your town.
Sources:
http://www.nationalbronze.com/News/what-is-naval-brass/
