What is Sandblasting? Process, Media, Equipment, & Alternatives

Sarah
DeGuzman

What is sandblasting? Sandblasting is the process of propelling media into a rigid object to clean or prepare the surface for further surface treatment. Despite the fact that it is technically called abrasive blasting, this method is commonly known as sandblasting. In this article, you will learn the sandblasting process, basic types of abrasive media used in the sandblasting process, equipment used, and alternatives to the process.

Sandblasting Process

Sandblasting stores abrasive media and using pneumatic means propels that media against a surface. This action removes old paint, rust scaling, and engraving, among other impurities. It smoothes a rough surface, roughens a smooth surface, or shapes a surface to remove impurities. The two types of sandblasting processes are water-driven and air-driven sandblasting. Water driven is the most common approach for preventing moisture buildup and intrusion on brick or concrete surfaces, whereas air driven is best suited for preventing moisture buildup and intrusion on metal surfaces.

Sandblasting requires appropriate safety precautions. Operators should safeguard their eyes, wear protective gloves, overalls, and respirators when directly exposed to blasting grit. A Positive pressure blast hood or helmet with a head suspension system allows the device to move with the operator’s head. Helmets should include a view glass with a changeable lens or lens protection and an air-feed hose. Hearing protection, and body protection further protects the operator during sandblasting.

Instruments and equipment utilized in this procedure may differ from one industry to the other. Some applications require hand cabinets or a whole robotics system, while others prefer a high-volume, dedicated automatic high-production variant. A key element to determining the end product is the type of media used during production.

Types of Media

Choosing the right abrasive media significantly impacts the quality of the finished product. It is crucial to select the best type of sandblasting media for the job. Abrasives may be grouped into three categories: mineral, synthetic, and agricultural.

Mineral Abrasives  

When operators wish to recycle sandblasting material, mineral abrasives provide a strong option. Silica sand, Garnet, and coal slag are examples of media in this category.

Silica Sand

This type of abrasive media breaks easily and produces a lot of dust. Silica sand fractures into fine particles and becomes airborne, posing a hazard to operators. Without proper PPE, silica sand inhalation causes silicosis, a devitalizing lung disease.

Garnet

More expensive than silica sand, Garnet provides an aggressive and sharp abrasive while reducing waste consumption. It provides an angular edge that cuts and rips off coatings as it flows across the surface of the part.

Coal Slag

This type of abrasive is a byproduct of a coal-burning power plant and often is used for general maintenance and repairs. Water blasting does not use this type of media because of the high amount of particles that can muddy up the surface.

Synthetic Abrasives

Synthetic abrasives categorize by the softness of their materials. Major options in this category, are aluminum oxide, silicon carbide, and glass beads.

Aluminum oxide

A sand-like material, aluminum oxide provides etching and finishing. It contains low iron content, thus reducing the probability of surface rusting. Aluminum oxide’s durability and use with a variety of metals provide two of its best qualities.

Silicon Carbide

Silicon carbide is a ceramic material that contains hard grains that break down under pressure. Commonly known as the hardest abrasive media in the market, its material hardness exceeds that of aluminum oxide. Many operators prefer this type of media due to its low cost and its long life span. It is also an excellent choice for removing rust, flaking paint, and contaminants from an object’s surface.

Glass Beads

Spherical, clear pieces of glass provide an excellent choice for applications that require a pliant and polished finish. While not as aggressive as other blasting media, glass beads provide adequate cleaning for most applications. Due to its ability to smooth surfaces and reduce burrs, glass beads frequently serve as the finishing operation for wood cabinets.

Agricultural Abrasives

This type of abrasive media provides gentle and economical coverage. They are environmentally friendly but see infrequent use due to the technological advantages of abrasive media designs. Major types include corn cob, walnut shells, and baking soda. Agricultural abrasives see mostly residential and commercial use.

Corn Cob

The hard cob material works best on soft surfaces like woods. They absorb oil and dirt specks without damaging the surface. Corn cob residue also cleans delicate parts. No matter the blasting need, corn cob grit lasts a long time and provides the best results.

Walnut Shells

Walnut shells provide long-lasting, all-natural grit with exceptional properties. They are inexpensive but efficient for cleaning, filtration, polishing, and blasting.

Baking Soda

Sodium bicarbonate, more commonly known as baking soda, provides a biodegradable and environmentally friendly option. Sandblasting soda can clean surfaces, remove paint and graffiti, and restore items when used with compressed air or water.

Equipment Involved

High-quality sandblasting results occur by properly understanding and using various sandblasting equipment. Portable blast equipment, blast cabinets, and blast rooms provide the main categories of blasting equipment

Portable Blast Equipment

Powered by diesel or a compressor, portable blasters can be wheeled to any location. Portable blast equipment may be dry or wet. Portable blasting makes sense for objects that cannot be physically removed and require on-site cleaning and restoration.

portable blasting machine
Courtesy: Fishing System

Blast Cabinet

The blast cabinet is a medium-size box that allows the operator to recycle abrasive after blasting. It typically consists of four components; blasting system, containment, abrasive recycling system, and dust collection system. Blasting is either dry or wet depending on the work requirements. A containment system or a sandblast cabinet typically provides a see-through window for visibility of blasting operations. An abrasive recycling system reclaims abrasive media after exiting the process. The dust collection system collects and gathers dust and fine particles produce during the blasting operation.

blast cabinet
Courtesy: Sandblaster

Blast Room

Blast rooms typically are much larger than cabinets and can accommodate large industrial products such as structural skids, pressure vessels, and e-houses. No matter the blasting equipment, all rooms share similar properties. The enclosure or containment system(the room itself) prevents the media from escaping. A dust collection system provides air filtration. A media reclamation system collects abrasive blasting media for reuse.

blast room
Courtesy: IST Blast

Alternatives

Generally known as the best solution for cleaning surfaces, sandblasting is firmly established in the industrial market. However, depending on the application, laser cleaning, pickling, or passivation may provide a strong option.

Laser Cleaning

Laser cleaning provides a strong alternative for dust removal and surface cleaning. Pulses remove contaminants with no impact on the underlying material. The use of sandblasting in cleaning applications can be effective, but it’s also risky. Laser cleaning, on the other hand, provides a safer, less damaging alternative to sandblasting. 

laser cleaning machine
Courtesy: Laser Photonics

Pickling Treatment

Pickling provides an acid-based solution that removes impurities, such as stains, rust, and aluminum alloy. Metals can become covered with dust and impurities and thus, affect the usability of the product. Pickling removes rust and any deteriorating surface impurities.

Passivation Method

Passivation provides a nitric acid or a citric acid-based bath. Counterintuitively, passivation creates corrosion on the surface. This increases corrosion resistance and creates a hermetic seal that blocks further corrosion.