Metals are the most abundant material on the planet. The Earth’s core, itself, is a gigantic ball of iron. You can find them in almost every building, vehicle, or machine, as well as most of the everyday items you use. They comprise 77 percent of the Periodic Table of Elements—and these are just the pure metals. The alloys produced by combining two or more of them are not yet included. Simply put, metals play a critical role in how the world runs, and yet a lot of people know very little about them.

There’s more to the metals that make up your doorknob and window frame than you probably know. If you take a closer look at them, you’ll find some fascinating facts that can make you understand how vital metals are to human life. One of the most interesting things about metals is their susceptibility to corrosion, a process that results from electrochemical reactions between materials and substances in their environment.

Understanding Corrosion

When a metal is placed in an unstable environment, its chemical composition changes, particularly when it makes contact with a reactant, a substance it reacts to. Different metals react to different substances and how they react varies according to their classification. Ferrous metals, for example, slowly transform into rust when exposed to oxygen.

Non-ferrous metals or those metals that do not contain iron, on the other hand, react by forming a protective outer layer called patina. The best example of a metal that undergoes this type of corrosion is copper and all its alloys. When exposed to oxygen, copper’s surface turns green over time.

Have you ever wondered why the Statue of Liberty has a green color despite lack of coating? That’s mainly because its cladding is made entirely of copper. After over 140 years of exposure to the elements, its copper covering has long reached the final stage of its transformation, which is colored green.

When You Don’t Always Want Green

While the green color of corroded copper looks appealing to some, it does not to others. If anything, they think the color doesn’t fit to certain decorative applications and they prefer dark brown, black, or anything in between. In that case, they prefer an alloy of copper where copper’s properties are not that prominent, so they choose bronze.

Bronze has been used for making statues, ornaments, and all kinds of accessories for thousands of years. Hundreds of bronze sculptures have been unearthed and displaced in many museums all over the world. It’s their thick layer of patina that preserved them for so long, some of them are still intact and need little polishing to look their best again.

Unfortunately, it might cost you a fortune to have any of these artifacts displayed in your own house. The good news is that these are not the only bronze sculptures available out there. There are bronze sculptures that, despite being created more recently, have almost the same distinct color and shade as those of the ancient artifacts. You may wonder how those who made them were able to achieve that. Well, the secret is to speed up corrosion.

How to Speed Up Bronze’s Corrosion

It’s actually no secret that bronze’s beautiful patina can be expedited. In fact, the technique called “intentional patination” became so popular that it has created a whole new industry. It involves exposing bronze to a variety of chemicals until the desired color and shade are achieved. The process is quite simple; anyone can try it at home if they don’t want to spend a lot on purchasing an already patinated bronze furniture or sculpture.

All you have to do is prepare your bronze sculpture by cleaning its surface and making sure it is free from any foreign elements that might get in the reactant’s way. Ferric nitrate is the safest and most cost-efficient choice for a reactant. However, direct application on bronze can cause rapid reaction, which is why it is advisable to apply an undercoat of bismuth nitrate.

The corrosion is usually aided by change in temperature, and so it is important to heat the bronze while applying the ferric nitrate. After covering the entire surface, start applying cupric nitrate to add complexity. Let the coating sit overnight and then wax the surface for finishing. The wax serves as a shield to preserve the color of the patina you’ve forced to come out.

Copper Supplies from the Right Supplier

If you are planning on a project that involves the use of copper alloys, particularly bronze bars, make sure you will get your materials from a trusted supplier, such as Rotax Metals. This is the only way to ensure that you will be able to achieve the right patina for your bronze. Whether it’s a simple bronze or a special one like Muntz metal, it helps you get it from the right source.

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.