Aluminum Oxide vs. Silicon Carbide: Which Abrasive to Choose?

Aluminum Oxide vs. Silicon Carbide: Which Abrasive to Choose?

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If you need any kind of abrasive grain to sand, scratch, or wear down any other material, then you have quite a few options to choose from. Sure, one of the most common types is sandpaper, but there are also far more specialized types of abrasive grains out there, mainly aluminum oxide and silicon carbide.

Although the two do share some similarities, they also have big differences, particularly in terms of what they are used for. Let’s compare aluminum oxide and silicon carbide abrasives to determine what exactly they are and which one is best suited for specific purposes.

What Is an Abrasive Grain?

Before we can start comparing different types of abrasive grains, you first need to know what they are.

So, by definition, abrasive grains are any sort of sharp and hard material that you can use to wear, grind, or sand down any other material when the two are rubbed together. In other words, they scrape and scratch away the surface layers of various materials to achieve a specific finish. Of course, the abrasive grain being used always needs to be harder than the material being worked on.

Some examples of abrasive grains include emery, sandpaper, pumice, and of course, aluminum oxide and silicon carbide. On a side note, you can even find diamond-studded sandpaper for the toughest of jobs.

What Is Aluminum Oxide?

Technically speaking, aluminum oxide is a chemical compound formed by the combination of oxygen and aluminum. Aluminum oxide is both very strong and hard, and is in fact one of the hardest materials out there, just slightly softer than diamond (which is the hardest material), but not by much.

Aluminum oxide is a widely used abrasive and is often used as a replacement for industrial diamond abrasives, as it is nearly as good as diamond, but much cheaper.

These abrasives are most commonly used in industrial applications, particularly for grinding and scraping tools, mainly cut-off tools. Finer versions of aluminum oxide may also be used for polishing purposes, such as for polishing DVDs and CDs. There are even some special varieties that can be used as a dermal abrasive for human skin.

What Is Silicon Carbide?

We then have silicon carbide, which is also referred to as carborundum. This is a very hard chemical compound that contains mainly silicon and carbon. In nature, it occurs naturally as a rare mineral known as moissanite, but is generally mass produced as a crystal or powder, and has been since the late 1800s.

One of the most common uses of silicon carbide is, of course, as an abrasive. This is a fairly low-cost material, which is one of the reasons for its popularity. This material is often used in lapidary, which is the practice of cutting and shaping stones.

As far as industrial applications go, it is often used in various processes including sand blasting, water jet cutting, honing, and for the grinding of various materials. Silicone carbide is often bonded with paper to form specialty sandpapers and is even used to form the grip tape on skateboards.

Similarities of Aluminum Oxide and Silicon Carbide Abrasives

Now that we know what both aluminum oxide and silicon carbide are, let’s figure out what makes them similar.

1. They Are Chemical Compounds

The biggest similarity shared by both of these substances is that they are chemical compounds formed by combining two or more chemicals or substances. Aluminum oxide is a compound that is formed by the combination of oxygen and aluminum, whereas silicon carbide is formed by the combination of silicon and carbon.

2. They Are Manufactured

Another similarity here is that in terms of modern use, both aluminum oxide and silicon carbide are manufactured in factory settings. Although they may occur naturally, they don’t occur in great enough quantities or aren’t cost-effective enough to extract from nature. Therefore, both are usually created in laboratory or factory settings using specialized processes, as it is easier, faster, and more cost-effective than trying to extract them naturally.

3. They Are Used as Abrasives

Of course, the other common similarity here is that both of these materials are commonly used as abrasives for a number of applications within many industries.

Differences Between Aluminum Oxide and Silicon Carbide Abrasives

Now that we know what makes both of these chemical compounds similar to one another, let’s figure out what makes them different.

1. Sharpness and Hardness

One of the biggest differences is that silicon carbide is both much harder and sharper than aluminum oxide, which is comparatively soft. Even with light pressure, silicon carbide abrasives excel at cutting or grinding glass, plastic, and metal. However, silicon carbide is not ideal for very hard metals and woods. If we are talking about bare metal, wood, and painted surfaces, aluminum oxide is the material of choice.

2. Durability and Longevity

Another difference between the two is that silicon carbide, although harder and sharper, which is, therefore, better for quickly grinding away at materials, does also wear down faster. The grain itself is much more fragile, which means that it doesn’t last nearly as long. Yes, jobs usually go faster with silicon carbide, but you will end up wearing it down much faster than aluminum oxide. Aluminum oxide works well on materials with high tensile strengths, as it won’t wear down as fast due to being used on very hard materials.

3. Wet and Dry Sanding

Another difference that many people don’t know about is that silicon carbide can be used for wet sanding applications that involve the use of water. However, due to the makeup of aluminum oxide abrasives, they can only be used for dry sanding. The aluminum oxide will lose a lot of its grinding or sanding power if it gets wet.

4. Applications and Usefulness

The reality here is that although both are useful abrasives, they generally work best for different applications. When working on materials that have relatively low tensile strengths, non-metallic objects, or low-tensile metals, silicon carbide is best. However, aluminum oxide tends to work better on materials with high tensile strengths.

5. Different Compounds

The other fundamental difference here is of course that although both are chemical compounds, they are made from totally different elements. One is made out of silicon and carbon, and the other out of oxygen and aluminum.

Aluminum Oxide vs. Silicon Carbide: Which One Should You Use?

The bottom line here is that if you need something super hard and sharp that can make quick work out of materials with low tensile strengths, then silicon carbide is best. However, if you need to work on very hard materials with high tensile strengths, and something that will last for a long time, then aluminum oxide is best.

On a side note, keep in mind that you can combine these two abrasives together to allow for a very smooth and fine cut without causing the abrasives to wear down too quickly.


As you can see, although these are both useful abrasives, their ideal function does differ quite greatly. Make sure to choose the right one for the application at hand, or else the result will not be as desired.