Aluminum and steel are the two most commonly used metals in manufacturing. However, despite their different properties and applications, it can be difficult to distinguish between them by appearance alone. Furthermore, aluminum and steel come in countless different alloys and grades, some of which look identical.
Ideally, metals come with some kind of identifying marking or documentation. However, there are plenty of scenarios where this is not the case, especially when dealing with scrap metal. How do you identify a metal when you’re not sure what type it is or where it came from?
When working with steel, aluminum, or any other type of metal, it’s important to know how to tell the difference between them. Depending on the metal, identification methods may be as simple as comparing color. Many metals, though, look virtually identical. Fortunately, there are other techniques to determine what material you’re dealing with.
Below, we detail a few simple metal identification methods to help distinguish between steel and aluminum, different grades of aluminum, and other metals such as copper, bronze, and titanium.
How to Tell the Difference Between Steel and Aluminum
Aluminum and steel have significantly different mechanical properties you can use to tell one from the other. Here are some simple identification methods for aluminum and steel.
The easiest method for distinguishing steel from aluminum is by using a magnet. Ferrous materials are magnetic, while most nonferrous metals are not. Simply press a magnet to the metal—it will stick to steel but not aluminum. However, it’s important to note that some stainless steels are magnetic, while some are not.
Aluminum is also much softer than steel, and this property is easy to test if you don’t mind scratching the metal. Press a key into a piece of unidentified metal that may be aluminum or steel. If the piece is aluminum, it will scratch easily and deeply with light pressure. Steel will scratch, but it takes much more pressure, and it won’t be as deep. This metal identification method gets easier as you practice and get used to how aluminum feels under the key versus how steel feels.
How to Identify Different Aluminum Alloys
There are dozens of aluminum alloys, and some are very different from each other. There are aluminum alloys that weld easily, while others don’t. Some alloys can be heat-treated, while others can’t be. If you know you have aluminum but not what alloy, how can you identify it?
Distinguishing aluminum alloys from one another without sophisticated equipment isn’t easy, but there are metal identification methods that can provide some useful information about an alloy. For example, if you need to determine whether a piece of aluminum can be welded, look at the surface finish. In general, if it’s bright and easy to polish, it will weld, but if it’s dull, it will not.
Determining the exact aluminum alloy requires equipment that can measure the material’s composition. The equipment applies energy to a sample of the metal and measures the frequencies of the resulting emissions. The methods can be destructive, like atomic emission spectroscopy, which requires the material to be atomized or burned, or non-destructive, as in x-ray fluorescence spectroscopy, which energizes the material by scanning it with x-rays. If you need an exact answer to what aluminum alloy you have, you’ll need help from a lab or other metal professional with access to one of these metal identification methods.
Other Metal Identification Methods
What about identifying metals other than stainless steel and aluminum? Many metals have distinctive colors that can help with identification. If a metal is bright, shiny, and reddish-brown, it’s most likely either copper or red brass. Copper also forms a pale green patina over time when exposed to the elements—this is the reason for the Statue of Liberty’s color.
Bronze is an alloy of copper and tin, so it has a reddish-brown color very similar to copper. Bronze has a dull gold, darker finish, while copper has a more pinkish-orange color. Bronze is also much more brittle than copper, so if a copper-colored metal is easy to bend, it’s copper.
Gold-colored metals are usually brass. Yellow brass has a similar color to metallic gold, but gold is darker and less yellow. Gold is also heavier and is much rarer, so it’s likely your gold-colored scrap metal is brass.
Keep in mind that metals may be oxidized, coated, or painted, so trying to identify scrap metal based on color can be misleading.
Purchase or Recycle Metals with a Local Metal Supplier
Whether you’re a machine shop owner, a metalworker, or you just need to recycle some scrap metal, Industrial Metal Service can help. We have been supplying steel, aluminum, and other metals to the San Francisco Bay Area and nationwide for over two decades.
What if you need to recycle scrap metal, but you still don’t know what type it is after trying the metal identification methods above? No problem. We verify scrap metal using x-ray fluorescence technology. Our handheld Thermo-Fisher XRF analyzers can identify the exact composition of a metal sample so we can assure that you’re getting the alloy and grade you need, and you know you’re getting a fair price for your scrap metal.
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