Aluminum Oxide vs. Silicon Carbide

Operations rely on blasting media for stripping, cleaning and polishing, which helps to create a sleek and professional final product. Aluminum oxide and silicon carbide are two popular abrasives for metal and wood finishing, and they are often compared to one another. While both are versatile and cost-effective, their characteristics make them ideal for some applications and less so others.

Aluminum Oxide Abrasives

Aluminum oxide blast media tends to be the most popular choice for use on painted surfaces, wood and most types of metal. These abrasives are also affordable and long-lasting to keep production up at lower costs. Aluminum oxide comes in three colors — pink, white and brown — each with different uses.

Pink and White

The white and pink forms of aluminum oxide create smoother finishes than the typical brown. White is most efficient for processes involving wood and lacquers because it generates less heat and offers exceptional performance in precision applications. Pink works best on softer woods and in sharpening or grinding operations. Their primary drawback is lower durability than the brown varieties.

Brown

Brown aluminum oxide, which works best on hard materials, offers affordability and extended wear because its grains take longer to deteriorate. The grits also sharpen themselves as they break, called semifriable grain. Coarser grains wear as they remove larger metal burrs, leaving smoother grains behind for more refined finishes.

Brown aluminum oxide is also highly recyclable, meaning it can handle many blast cycles before needing a replacement. As a result, this option is the most cost-effective blasting abrasive.

Silicon Carbide Abrasives

Like many carbides, silicon carbide blast media is sharp and extremely hard. This toughness makes the abrasive perfect for ceramics, glass, stone, marble, fiberglass and many plastics.

Silicon carbide contains narrow, pointed edges, and you can use it several times without replacement for shorter blast cycles on softer materials. It etches well and prepares the underlying material for finishing coatings. Yet, its hardness can generate faster wear and makes it a less suitable choice for wood or harder metals like steel.

Versatility is the most significant advantage of silicon carbide blasting media. You can use silicon carbide in either direct-pressure or suction-based systems. You can also use it alongside aluminum oxide in finishing operations — the latter for general residue removal and the former for polishing. You’ll save wear on the less durable silicon carbide abrasives while still creating smooth finishes in either individual finishing or blast tumbling.

Silicon carbide is safe for use in wet or volatile environments. It produces no static electricity that can ignite and has very little magnetism. These abrasives offer both friable and nonfriable options to extend the wear.

Is Aluminum Oxide or Silicon Carbide Best for Grinding Steel?

Aluminum oxide is the better abrasive media for grinding steel. While silicon carbide is sharper and harder than aluminum oxide, it’s also more brittle. This brittleness will cause it to wear rapidly on a hard surface like steel. If you try to use silicon carbide on steel, you would likely have to use several rounds of the abrasive to see any effect on the surface.

Aluminum oxide is highly durable. When grinding steel, brown aluminum oxide will present the most beneficial qualities for a moderately smooth steel finish. You might use pink aluminum oxide after brown to refine the surface further.

Is Aluminum Oxide or Silicon Carbide Best for Grinding Aluminum?

Aluminum is a soft metal and benefits from a mixture of aluminum oxide and silicon carbide. When working with aluminum, you need a hard abrasive for an even finish, but you want to minimize heat generation. Silicon carbide offers ideal qualities for low-tensile strength metals like aluminum, so it may work well on its own. However, it depends on your applications.

You might start the grinding process with aluminum oxide, then refine it with silicon carbide. White aluminum oxide is an excellent choice for aluminum surfaces because it offers precision without generating too much heat.

Choosing Between Silicon Carbide or Aluminum Oxide

The choice between aluminum oxide and silicon carbide depends on your application. If you’re working with non-metallic or low-tensile strength materials, consider silicon carbide. Aluminum oxide is better for high-tensile strength materials like steel, bronze and aluminum alloys.

Using a combination of the two is recommended for precision refining. While aluminum grinding is an example of using both, it’s also an ideal practice for woodworking applications, too.

Get the Blast Media You Need at Finishing Systems

The experts at Finishing Systems can help you find the right abrasives for your applications. We carry aluminum oxide and silicon carbide to support your stripping and finishing goals. With friable, semi-friable and standard varieties, our products have maximum versatility. Get in touch with us today.