With so many different kinds of metals available commercially, it is easy to get confused between multiple choices, especially if the variations are very subtle. Metals of the same basic element are even more difficult to classify because they often share qualities. (more…)
Have you ever wondered why the handful of metals you are familiar with are in fact the rarest ones? Gold, silver, bronze, even platinum aren’t particularly the most common of metals. Unlike steel and iron, you don’t see a lot of them inside your home, in the streets outside, or in the workplace. They are simply very rare, and that’s because they are difficult to unearth and manufacture, which is also why they have higher monetary values than more common metals.
One of them, however, even though prized similarly, is actually very common. Not in a sense that you can see it everywhere, but certain components of many everyday objects are made from it. That metal is bronze. You’ve probably heard of it at least once or twice. You probably even know what it looks like and how it’s metallic brown color sets it apart from the rest of more pleasant-looking metals. But I’d bet you know only a few object that are legitimately made of bronze.
Bronze is an alloy of copper and tin. Its composition varies but most of today’s bronzes are made of around 80 percent copper. Other elements, such as manganese, aluminum, nickel, phosphorus, silicon, arsenic, or zinc, to produce different types of bronze, each having a unique set of useful properties. Here are some of the most common types of bronze produced by adding an extra element to the original alloy.
When you mix about 6 to 12 percent aluminum into the original copper-tin mixture, you produce a stronger and more corrosion-resistant bronze, called aluminum bronze. Aluminum is well-known in the construction and mechanical field for its many valuable properties, including high diffuse reflectivity, low secondary heat emission factor, tolerable toxicity range, and reasonable heat and electrical conductivity. All of these properties are adopted by bronze right after the alloying.
Despite not having the word “bronze” in its name, nickel silver is actually a type of bronze. It consists of bronze, tin, and nickel. And despite having the word “silver”, this type of bronze actually doesn’t contain silver. The silver only refers to the metal’s silvery color, which is not characteristic of bronze. This vast difference in appearance is one of the main reasons why identifying products or objects made of bronze can be quite difficult. That’s mainly because consumers are accustomed to seeing bronze as the brown metal.
Adding a miniscule quantity of phosphorous can make bronze incredibly strong. It can increase bronze’s yield and tensile strength several times, depending on how much of it you add to the mixture. Ideally, only between 0.01 and 0.35 percent of phosphorous should be added to avoid turning the strength into brittleness. Apart from strength, phosphorus also helps improve bronze’s fatigue resistance, durability, and coefficient of friction. This is what makes phosphor bronze highly suitable for applications that involve constant and rapid sliding of metal surfaces.
Known for its easy pouring ability, appealing surface finish, and superior corrosion resistance, silicon is almost the perfect alloying metal. Silicon also happens to fit perfectly into the bronze alloy. Even if only about 6 percent of the entire bronze alloy is made of silicon, it is enough to give bronze the self-lubricity it needs to be easily formed or cast into different shapes and intricate details.
Manganese can make bronze hard and strong as well. This allows bronze to handle high-load, low-speed applications, which originally are among its few weaknesses. The high bearing strength manganese endows, however, also turns bronze into a non-heat-treatable metal, which is why special lubrication is needed for applications involving the use of manganese bronze.
While each type of bronze has a unique set of properties thanks to the extra element they contain, there are certain properties that they have in common. These are the properties that determine the plethora of uses of bronze metal.
Although bronze is an excellent material for sculpting, it is one of the hardest copper alloys around. Its hardness depends on the proportion of its original content and the additional element it has. Nevertheless, it can withstand pressures ranging from 35,000 psi to 119,000 psi. The hardest of all types of bronze is manganese bronze as it can hold up to the maximum tolerable pressure.
Unlike other copper alloys, bronze doesn’t melt very easily. It would take up to over 2000 degrees Fahrenheit of heat to melt bronze. What’s astonishing about this property of bronze is that it gives us a clue as to how resourceful our ancient ancestors were. It’s amazing how they were able to produce heat of that scale using primitive methods to product bronze, and they were able to repeat the process over and over.
Having constituents that are all resistant to corrosion, it’s not surprising bronze is corrosion resistant as well. It doesn’t rust like iron or steel and some of its types, such as Muntz metal, can even hold up to saltwater, which is ten times more corrosive than tap water. Instead, it forms a layer of protective finish called patina. This is common among copper alloys.
Bronze has seen a sizeable decline in utilization ever since steel and other metals with more suitable construction applications had been discovered. Then again, bronze has evolved to become useful in many other applications, thanks to the metallurgists who have spent their lifetime exploring the virtually limitless potentials of this metal. Here are some of the most common uses of bronze.
Perhaps the most popular use of bronze is in art, particularly as a base material for sculpture. It is the material of choice for sculptors specializing in metals because of its amazing property, which allows it to slowly expand as it cools down. Although heavy and dense, bronze is quite easy to work, allowing sculptors the freedom to chisel at their hearts’ content.
Despite being superseded by steel in an array of construction-related applications, bronze still preserves its place in some of them. For instance, many movable bridge components, wheels in worm drives, and turntables for bridges are made of a certain type of bronze. Modern safety tools such as hammers, mallets, and wrenches, are also made of a type of bronze. These tools were originally made of steel, but because of the risk of fire or explosion caused by the unsafe sparks steel can make, steel was replaced with bronze.
There are a score of machine parts that are best made of bronze—spur gears, bushings, bearings, valve components, and even valve guides in aircraft engines, all thanks to its high electrical conductivity, thermal resistance, and low-friction properties. Not very many metals exhibit low-friction qualities, which is very crucial in settings where parts slide against each other at a high rate.
Now that you have at least basic knowledge of bronze, we suppose you already know your way around it when you plan on using it for any of your future projects. Of course, the success of those projects also depends on the quality of the bronze materials you will use. Always partner with a supplier who not only specializes in copper alloys like bronze but also has their own foundry. It pays to have a bronze tube and bar supplier who can provide you with the highest quality materials you need anytime.
Despite its superb corrosion resistance, brass tarnishes considerably fast. It can lose its original luster within hours after being exposed to moisture, or even just to air. Thankfully, the tarnish on brass can be removed just as fast with proper polishing. But before we teach you how to bring your brass items back to its shiny self, let us first get to know brass more.
When we think of brass, the first thing most of us would imagine is a musical instrument, such as a trumpet or a trombone. That’s because brass instruments are perhaps the most famous types of objects made of brass. Very few have a clue that brass extrusions, bars, and tubes are also very common. This is a metal that consists of copper and zinc. Sometimes, a minute quantity of other elements, such as arsenic, lead, phosphorus, aluminum, manganese, or silicon, are added to improve its properties.
Brass owes its corrosion resistance from its copper content, although zinc is itself corrosion resistant. Like copper, brass slowly forms a patina on its surface when exposed to the elements, as opposed to other metals, particularly the ferrous ones, that form rust instead. A patina is a thin layer of material that develops as a reaction of copper molecules on the surface of brass when they make contact with oxygen molecules.
Unfortunately, not everyone is attracted to the rustic appeal of patina. While some want their brass items looking elegantly antiquated, others want to keep them shiny at all times. The initial process of patination is characterized by the formation of tarnish, so those who dislike patination should deal with it when it’s just in the form of tarnish. Unsurprisingly, tarnish is much easier to remove than a full-grown layer of patina.
As mentioned, tarnish is undeveloped patina, but how does it really form? The best way to find out is to put a piece of brass under an electron microscope and observe how its molecules interact with the air or with any other object or substance placed on its surface.
When copper and zinc are combined, they form a rather unique assembly of molecules. The atoms comprising these molecules share valence electrons with one another. Those that have already lost their valence electrons become ions, and they are the ones responsible for the formation of tarnish. When ions of brass interact with ions of moisture or air, a layer of chemical compounds that have a different color from the metal itself emerges. Occurring in stages, this layer starts out as dull tan and leads to dark gray, blue, or green. Let me give you some good tarnished brass cleaning tips.
As previously explained, it is easier to remove patina during its early stages, specifically when it’s just in the form of tarnish, so it shouldn’t be difficult to clean your brass item at this point. There are two ways to go about it—naturally, using natural and everyday products, and with the aid of chemicals. Regardless of your preferred agent for cleaning tarnished brass, however, here’s what you should do to get tarnish off your brass items.
Brass is often used for decoration because it resembles gold. This mimicking feature is not unique to brass, though, because other metals can look the same as brass with the right alloying or coating. If you’re not careful and you start cleaning your item without making sure it’s really brass, you might damage it with the chemicals you bought. To determine whether or not your item is really brass, hold a magnet to it. Brass is not magnetic so if the magnet sticks, your item is not brass and may need a different polishing approach. Ironically, if your item isn’t brass, you may not even need to polish it because it wouldn’t have tarnish in the first place.
Lacquer is a clear coating applied on the surface of metal to give it a protective shiny finish. It’s quite easy to tell whether your item is lacquer-finished or not simply by wiping it with a clean, dry cloth. If the surface immediately turns shiny again, it means it has lacquer on it. That’s because lacquer is meant to preserve the shiny appearance of brass, like a laminate on your windshield. It only turns dull-looking when it’s already cloaked with dust and grime. The reason you should do this test is because you might damage the lacquer with metal polish. Considering that lacquered brass has its shiny surface preserved, polishing it is not a good idea.
Before you start scrubbing the surface of your brass item, wash it first to get rid of excess dust and grime. These contaminants may consist of tiny sharp-edged stones that might scratch the surface of your brass item if they get mixed up with the soap suds that you will scrub with the cloth. After rinsing, dry the item very carefully so no trace amount of water will be left on its surface. Water can dilute your metal polish and reduce its potency.
If you opt to polish your brass item using a commercial product, all you need to do is to go to your nearest hardware store and look for one that is neither too harsh nor too mild for your brass item. The supplier would normally know what you need if you give them as much information about your brass item as possible. In case you want to try natural products, that’s where you need to conduct a little chemistry experiment at home.
There are scores of products around the house that you can use as a polishing agent, of which the most widely used is the baking soda – vinegar solution. Other products that contain a little bit of acid, such as ketchup and lemon juice, are also good for polishing. Just make sure you will mix the right amount of each ingredients to avoid making the solution too harsh for your brass item. You don’t want to scuff a significant layer from the surface of your item as you buff it up.
Slowly apply the solution on the surface of your brass item. Make sure every groove and section is covered with the solution, and then wait for it to dry before you start buffing with a clean cloth. As you scrub through the surface, you will notice the dark, old surface slowly disappearing and the shiny layer underneath finally emerging. Don’t stop until the entire surface of your brass item is free of patina.
The truth is, you can’t prevent tarnish from forming, but you can delay its formation. As previously explained, the only way to preserve the shine on brass is to keep the elements at bay, which is quite tricky. You can, of course, apply lacquer, but even this amazing coating would soon succumb to the elements and disappear. What you can do is either to regularly polish your brass items or allow it to patinate.
Brass’s susceptibility to tarnishing may also have to do with its quality. Low-grade brasses usually have lower corrosion resistance than those manufactured by top brass suppliers, such as Rotax Metals. Therefore, it is important that when looking for brass materials to use in your projects, always go to a supplier that runs its own foundry and has been in operation for many decades to make sure of the quality of the products you will purchase.