Gold, silver, and bronze are three very popular metals, and for one quite odd reason—they represent the order of winners in a competition. Perhaps this old ranking system was based on the differences of these metals in terms of their physical attributes and perceived value. Gold, being the rarest and having the highest monetary value among the three, ranks first. Silver has certain similarities to gold except the yellowish shade, so it follows behind. Bronze, the least visually appealing and the most commonly produced among them, ranks third.
In a metalworker’s viewpoint, however, this order does not apply. In fact, if the metals will be ranked according to their usefulness, the result might be the exact opposite. You will easily understand why bronze is more useful than either silver or gold upon identifying its different properties as well as the many extensively used alloys it has spawned over the last couple of millennia.
Useful Properties of Bronze
Bronze is an alloy of copper and tin, so primarily it exhibits the chief characteristics of both metals. It also exhibits new properties that are unique to the combination, each of which can be improved by either manipulating the content ratio or adding other types of metal into the mixture. Here are some of bronze’s known useful properties.
Ductility. Both copper and tin are ductile metals so bronze is expected to be ductile as well. It can be stretched or drawn into wires of different cross-sectional diameters without breaking, so much so that a lot of springs, strings, and other types of gear found in an array of instruments are made of this metal.
Low Friction. When two objects are rubbed against each other, they produce friction, which is characterized by the gradual rise in temperature of the materials in question. In mechanical design, friction means heat, and heat means decrease in performance or potential wear and tear. Bronze is known to show very low friction against other metals, making it a perfect material for certain machine parts.
Patina Formation. Quite a number of metals are capable of forming a protective shield on their surface when exposed to oxygen (to prevent further oxidation), mostly copper alloys. This layer of protective shield is called patina. Bronze is one of them, and in fact the most well-known patina-producing metal. It usually develops a greenish patina, which for many sculptors and antique collectors is a priceless characteristic to boot.
Does Not Generate Spark. Aside from heat, most metals produce spark when they collide against each other. This poses risk of fire if not managed properly. And so it is preferred to simply design mechanical systems using metals that do not spark when struck with other metals. Bronze is perfect for such applications.
Different Types of Bronze
Different types of bronze can be produced by manipulating its content. By reducing or increasing either copper or tin, a new type of bronze with a different set of characteristics can be produced. Here are some of the most widely used variations of bronze.
Aluminum Bronze. Although bronze does not rust or react badly to oxidation, there are other corrosive forces that it’s not tough enough to resist. To improve its corrosion resistance, it must be combined with a metal that is well-known for such property—aluminum. By adding up to 12% of aluminum, you can come up with a bronze that performs better in pressurized environments. More commonly known as aluminum bronze, this new alloy is an excellent choice for making marine hardware and pump systems that deal with corrosive chemicals.
Phosphor Bronze. One strange thing about alloys is that a tiny shift in the content ratio can have a huge impact on the properties of the original metal. In the case of phosphor bronze, for instance, only about 0.35% phosphorus is added and yet bronze’s strength of is almost doubled. This is not to say that adding more phosphorus makes bronze even stronger. Only in this exact amount will you be able to produce such an incredibly strong material. Phosphorus bronze is utilized for making electrical components, washers, springs, bellows, and more.
Nickel Brass. You may think that there’s some kind of mistake and nickel brass shouldn’t be in this category. In truth, it’s just called “brass” but its content is essential bronze. Formed by combining copper, tin, and nickel, the brownish shade of bronze turns into a silvery one. Apart from the unique shade, it also improves bronze’s corrosion resistance. The word “brass” in its name most likely came from the fact that several brass instruments are made of this metal.
Silicon Bronze. Silicon bronze consists of copper, tin, and guess what, silicon. Zinc is also added in most cases but only in trace amounts to prevent confusing the resulting metal with brass. The combination makes bronze more resistant to rust when exposed to moisture. And since silicon converts the ability to produce patina into natural resistance against oxidation, you can expect silicon bronze to keep its original look without turning into green or brown.
A lot of other alloys can be produced by tweaking the composition of bronze, and many of these alloys are already available on the market. You can see them as bronze tube, sheet, and bar items in supply stores. If your project requires a specific type of bronze, such as Muntz Metal, don’t hesitate to go to any of the country’s most reputable supplier. Rotax Metals is one of those suppliers you should go to first.
What Is Bronze? Definition, Composition and Properties, thoughtco.com
The Characteristics of Bronze Metals, sciencing.com