What is an Abrasive?
The most recognized abrasive is sand. Silica Sand, mineral sand, flint and garnet are all natural abrasives. Manufactured abrasives are produced and used specifically in the sandblasting industry and include: steel grit, shot, plastic, glass bead, aluminum oxide, and silicon carbide.
Abrasive- the abrasive is propelled from the sandblasting nozzle at high speeds sometimes dry sometimes wet depending on the surface targeted. The abrasive is under high pressure from compressed air. The abrasive does the work and sandblaster directs the stream. Selecting the right abrasive for the job is crucial. Selecting the wrong abrasive for the targeted surface can result in expensive rework or in the case of concrete a new pour. Keeping this in mind selecting an experienced sandblasting company will save you time and money.
Common Blasting Abrasives
• Silica sand – from beaches and rivers is rounded and softer than the other types of sand. Crushed silica sand from quarries is angular and harder, providing deeper surface profiles than rounded sand. Silica sand is widely used because of its availability, cleaning efficiency, and low cost.
• By-product abrasives – such as slag and some agricultural media are generated from another process, but prove to be highly effective as blast cleaning agents.
• Slag – Slag’s hard, angular particles enhance speed and cutting ability, making it suitable for a wide spectrum of uses. In some applications, it may even be necessary to reduce nozzle air pressure to avoid embedding slag particles in steel.
• Enviro-Grit Abrasives – Crystalline Silica-Free, environmentally friendly and made from recycled glass
• Walnut Shell – A relatively soft nut shell abrasive for removal of coatings without etching, or scratching.
• Glass Beads
Abrasives Vary in Size
Abrasive size is very important. The sandblaster will have more consistent blast patterns when using the right abrasive. Many media manufacturers use numbers to describe abrasive size. Size becomes extremely important when following surface preparation specifications determined by a coatings supplier. Oversized particles can cut to deep leaving high peaks protruding above the coatings. This failure to follow specifications will cause coatings failure. Undersized particles and dust reduce productivity and may neither clean the surface adequately nor create sufficient etch.
Abrasive shapes also effect surface profile. Angular abrasives have sharp edges these will leave peaks and valleys in the prepared surface. Rounded particles leave dimples. impart different surface profiles. In angular abrasives, individual particles have irregulars shapes with granular surfaces and sharp edges to remove coatings and leave sharply defines peaks and valleys. Rounded particles produce dimples.
Hazards Associated with Abrasives
Dust is the major concern when dealing with abrasives. No dust is safe always where respiratory equipment when at a sandblasting site (refer to the Silica Page for information regarding silicosis). Always give a sandblaster room. Abrasives are projected at an extremely fast rate. Abrasives propelled at this speed can kill.