Sizing up cleaning abrasive media

YouÕve heard of using manufactured abrasives like walnut shells or baking soda for cleaning, but do you know which media to use?

The following is a short course on such sand alternatives. Most natural abrasives like silica, mineral sands, and garnets are considered expendable and are good for outdoor blast applications. Manufactured abrasives such as glass bead, aluminum oxide, silicon carbide, and plastic are reusable and employed in systems that recycle the material.

The shape of the abrasive has a huge impact on the speed at which it works and the finished job. Angular, sharp, and irregular shaped abrasives will clean faster and etch the surface. A round and spherical abrasive cleans parts without removing any of the base material. The hardness will influence how fast the material cleans, how smooth the cleaned finish is, and how much dust is created during blast cleaning.

Here is a list and description of common abrasive cleaning media:

Silicon Carbide: This is the most aggressive media on the market since it is both very hard (almost as hard as a diamond) and is blocky and sharp in shape. It is typically used when very fast material removal is required and is an excellent abrasive for deburring stainless steel and titanium parts.

Aluminum oxide: This is a cutting abrasive that is blocky and sharp in size and has almost an unlimited life span since it is so hard and resistant to breakup upon impact. It is the most commonly used cutting abrasive and an excellent choice when working with metals or hard, brittle parts. The media uses its sharp edges and hardness to chip off tiny pieces of the surface. Common uses for aluminum oxide include cutting, deburring, and removal of paint and rust from surfaces.

Crushed glass: This abrasive is manufactured and works well as a mild abrasive. It has the hardness of glass beads but with sharper edges. It is most often used when only a light degree of abrading the surface is required.

Walnut shells: Ground walnut shells are often the largest of all cleaning abrasive media, heavier than aluminum oxide, blocky in shape, and very resistant to breaking up upon impact and thus last longer. They are gentle enough to remove polymer coatings from a circuit board surface, or for cleaning metal without altering the surface finish.

Plastic: Plastic is second in size to walnut shells and also offers a blocky shape. It is good for stripping soft materials such as paint from harder surfaces without causing dimensional changes.

Glass beads: The spherical shape of glass beads keeps it from cutting into metal surfaces. It is good for light deburring, putting a satin finish on a part, removing surface particles, and relieving stresses by peening a partÕs surface.

Sodium bicarbonate: This is one of the softest abrasives on the market. The needle-like shape of its particles makes it good to use for abrading pliable materials. It is used to remove coatings on circuit boards without damaging individual components, for example. And because it is water soluble, removing residue after cleaning is easier. However, the media requires special equipment to use.