Recyclable Abrasive Blast Media

Many types of abrasive blast media can be re-used multiple times. The rate at which the media fractures during blasting will determine the recyclability. Media such as Steel Shot have an extremely high re-use rate while more consumable media such as Crushed Glass Grit can only be blasted once or twice. This chart details the recyclability of many common abrasive blast media.

Some factors to consider when selecting a media (as it relates to re-usability):

• Blasting system: Blasters that automatically collect the media (i.e., cabinets, blast rooms) make it much easier to use recyclable media.
• Cost: Typically, re-usable media are more expensive to purchase; however, the re-usability can make these media very economical.
• Surface finish: The hardness and aggressiveness of the media is not directly related to re-usability. Consider the surface finish required in combination with the recyclability.
• Cleanliness: Collected used media can also include contaminants that can reduce efficiency (i.e., dust particles), impact blasting performance (i.e., paint chips blocking the nozzle) or even damage the surface (i.e., concrete chips or small stones). Be sure to screen and clean the media as best as possible.

Abrasive Blasting Media - Steel

This final installment of the Abrasive Blasting Media series will discuss the merits of using both Steel Shot and Steel Grit for blasting. Both of these media types are produced from scrap steel which is melted, modified and then solidified into a generally round shape (Shot) or angular particles (Grit).

Steel Shot produces a very smooth finish on the surface of metals. The rounded shape does not strip a surface very effectively but rather peens the surface to produce a clean, smooth and (sometimes) polished finish. The smaller the shot the better the polish but the less aggressive the peening operation. The peening action of the shot is also used to impart compressive strength or hardening to metals.

Steel Grit is used when aggressive stripping action is required. Steel is softer than Aluminum Oxide so will not fracture as easily but the higher density produces a forceful blasting process. Smaller sizes and softer formulations of grit are used when lighter cutting is required while larger sizes and harder steel formulations will maintain the particle angularity and a high strip rate.

Since both Steel Shot and Steel Grit have a high bulk density of about 250 pounds per cubic foot, special or modified equipment is necessary to blast these media using air pressure alone. Steel is often used in wheel blast operations where the media is propelled by a wheel using controlled force.

Abrasive Blasting Media - Crushed Glass Grit

Traditional sand blasting and the need for healthy and environmentally sensitive operations meet up perfectly when using Crushed Glass Grit. Glass has the same hardness and other blasting properties as silica sand but none of the inhalation dangers from free silica. Crushed Glass Grit is 100% recycled glass diverting this material away from landfills.

Crushed Glass Grit is available in a wide variety grit sizes making it suitable for many different applications. Coarse sizes can be used for heavy duty stripping of paint, rust and other coatings off structural steel, concrete, brick and other structures. Fine sizes can be used (if careful) on thin metal surfaces such as automobile door panels without warping and even on wood surfaces without etching.

With recent performance and environmental approvals from the military and government agencies, Crushed Glass Grit is increasingly being used as a replacement for coal slag and other 'dirty' media. As Glass contains no heavy metals or free silica this media is showing increasing versatility as an economical, consumable blasting media.

Abrasive Blasting Media - Introduction

There are many different types of abrasive blasting media available. Each of these media will produce a different finish on the surface being blasted. The finishes can range from ultra-rough to nearly polished to no affect at all. There are many variables that determine the surface finish achieved including blasting pressure, angle and distance of the blasting, hardness of the grit media, blasting time, etc.

Knowing the basic differences in abrasive blasting media is required to determine the optimal process for different applications. In addition to the media type, grit or mesh size is another factor to consider. The final choice of media depends on the nature of the work required and on the blasting equipment that is employed.

The series of posts to follow this one will deal with abrasive media selection only and outline some of the advantages of the different types of blasting media and some guidelines for choosing the best media for your application

Wood Stripping

Question: I’m renovating a house built in 1917 and I would like to remove the years of built up paint off the 6 panel doors and trim that was used in the house. There are 15 doors and probably a 1000 lineal feet of various finish boards. Which Machine and Media should I purchase? Approximately how much media will I need?

Response: Either the KF110DM or the KF65DM will work with the Corn Cob Grit or Walnut Shell Grit. The Walnut Shell Grit will offer a more aggressive stripping action but the surface may require some sanding depending on the surface finish you require. Corn Cob Grit will be more ‘sensitive’ to the wood surface but will not strip as quickly.

The quantity of media required will depend on how aggressive the blasting that is required. Multiple layers of durable paint will demand more media; however, both Corn Cob and Walnut Shell are re-usable. If you are blasting in a clean area you can pick up the media and re-blast it a few times – just be careful to not pick up anything that could be blasted and damage the wood surface.

Aluminum Oxide

Aluminum Oxide (a.k.a. aluminium oxide, alumina, aloxite, corundum) is generally sourced from bauxite ore. While bauxite is the primary ore for aluminum metal, Aluminum Oxide is extracted using the Bayer Process to remove unwanted impurities.

Aluminum Oxide is a very hard, versatile blasting media that can be used in a variety of applications for removing oxidation and scale off metals to etching stone and glass surfaces. The pure (>99%) White Aluminum Oxide is used when surface non-contamination is critical like when blast cleaning medical parts.

The hardness and large grit sizes available also make Aluminum Oxide an excellent choice for non-skid flooring. Aluminum Oxide is commonly used as an abrasive for sandpaper.

I'll bet you didn't know that precious stones like rubies and sapphires are simply Aluminum Oxide (corundum) crystals contaminated with other metals like chromium, titanium and iron.