Everything You Need to Know About Sandblasting

Sandblasting typically used for cleaning, etching, or preparing surfaces before painting or coating, has been in existence for decades. It entails the use of compressed air to blow abrasive material in the right manner to get the intended impact. Contrary to the name Sand Blast, sand is no longer used because of health hazards and environmental issues. Today more suitable material is used and the process is known as “dry abrasive blasting. ” Sandblasting was first patented in 1870 by General Benjamin Chew Tilghman who noticed that sand had abrasive properties in the desert and later by Thomas Wesley Pangborn in 1904 who added compressed air.

What Is Sandblasting?

Abrasive blasting is the same meaning as sandblasting. It’s a widely employed technique to clean surfaces, strip contaminants, and even change surface profiles. This process involves abrasive material being held against the surface via the compressed air. Sandblasting stands as an effective, affordable method, performed for different purposes in industries and maintenance. The process can be adjusted depending on the material type, being worked on. For less strenuous work, for example, when stripping old paint or cleaning delicate surfaces then softer abrasives and less pressure are applied. On the other hand, if the task is more demanding, it is possible to use more severe abrasives and increase the air pressure. Sandblasting is more flexible than the others because it can be used for various purposes starting from metal rust removal to surface preparation for painting.

Furthermore, the process provides several abrasive materials. They include glass beads, walnut shells, or aluminum oxide depending on the need of the particular job being done. In this case, depending on the application, soft media are used to prevent scratching of the delicate surfaces. Further, to prevent connectors corrosion.

How Does Sandblasting Work?

The sandblasting process can be categorized into two ways:

Air-Driven Sandblasting Process

• Surface Preparation: When preparing the surface for substrate application, it’s essential to wash the area, which is to be treated. Any coating, rust contamination, or other foreign material required to be removed, should be marked on the surface.
• Loading Abrasive Material: Pour the chosen abrasive material into the container of the sandblasting equipment. The two most popular materials, such as aluminum oxide or glass beads, are used depending on the surface to be treated.
• Introducing Compressed Air: In this method, the abrasive material is thrown toward the surface by high-velocity air, created by compressing the air. For this reason, it is necessary to change the pressure depending on the material condition.
• Blasting the Surface: The operator then oscillates the nozzle in a systematic overlapping manner to clean the surface. The nozzle is adjusted for the sake of changing the spray.
• Inspection and Cleanup: Pausa from time to time to check whether the surface is clean enough or has the right texture.

Water-Driven (Wet) Sandblasting Process

• Surface Preparation: This is followed by surface preparation and the surface is then inspected for contaminants in the same way as in the air-driven process to determine the right abrasive to use and the settings.
• Mixing Abrasive with Water: Add water to the abrasive material to reduce dust production and control the temperature when working on the material.
• Compressed Air Propulsion: The slurry is propelled through the nozzle by the air pressure. The wet sandblasting process is less abrasive than dry blasting and relatively more precise.
• Blasting the Surface: Turn the nozzle to ensure an even spraying system. To clean, glide the nozzle over the surface slowly to ensure the surface is clean without causing any harm to it.
• Inspection and Cleanup: From time to time, it is necessary to check the surface to see whether it has changed or not. Then it is required to wash out the rest of the slurry and scraps and level the surface for the subsequent processes.

Sandblasting Machine Components

The sandblasting process relies on two key parts: the blast pot, and the air intake. The blast pot contains the abrasive media and discharges the same through a valve into the system. On the other hand, the air intake with the help of an air compressor creates the required pressure to circulate the media in the system for blasting.

Pressurized Abrasive Flow

Compressed air from the compressor then directs the abrasive media through the blast pot and a nozzle. This results in a highly concentrated stream of abrasive material at high velocities. The force generated guarantees that the media can clean the surface, strip off any coating, or change the surface texture.

Surface Impact and Material Removal

When the abrasive media impacts the surface, it breaks off dirt, rust, paint, or any other undesirable matter. It also can smooth or roughen the surface depending on the type of abrasive that is used. It is influenced by factors such as the type of media used, pressure in the air, and the material used on the surface.

Abrasive Media Recovery

Most of the modern sandblasting systems come with recovery technology. This system collects the used abrasive media, purifies and returns it to the blast pot and this makes the system to be very efficient. This not only cuts wastage but also aids in the reduction of cost and therefore the environmental impact.

Media Selection for Sandblasting

The right media must be used in sandblasting to get the best possible outcome. First of all, one has to choose whether to use wet or dry abrasives. Wet blasting is generally less effective. The former removes less material but is more suitable for hard coatings such as iron phosphate and epoxy paints. However, it is disadvantageous for nozzles because it increases pressure and thus wears them out faster.

Size and Shape of Abrasive Material

The size and shape of the abrasive particles are of great importance. Normally, the sieve analysis method is used to sort particles. This in turn helps in determining their mesh size and roundness. Larger and sharper particles are effective in removing dirt and stains within the shortest time possible; however, they are likely to cause damage. That is why, smaller or softer particles may not clean the deeply pitted surface adequately.

Selecting the Right Blast Nozzle Diameter

To find the optimal size for your blast nozzle, consider these key factors:

• Air Compressor Output (CFM): As you are using your compressor, discover the amount of air that it can deliver in one minute. This measurement is quite important as it assists in determining the right size of the nozzle that is to be used.
• Required Nozzle Pressure (PSI): Discover the pressure you need to retain for blasting which is most probably 100 PSI.

As mentioned above, the more CFM your compressor provides, the larger the blast hose and nozzle size which is useful in signifying blasting efficiency.

Sandblasting Media

Originally, sand was most commonly used abrasive in sandblasting. Because it can easily be obtainable. However, sand has some demerits such as moisture content and contaminants which ultimately affect the product quality. Moreover, sand produces silica dust fumes. These fumes in long-term exposure result in respiratory diseases such as silicosis and lung cancer. Therefore, sand has been replaced by several other safer materials of the modern world which are used as abrasives.

The type of blasting media to be used depends on the kind of surface finish or intended use of the blasted material. Here are some common alternatives:

Aluminum oxide grit

is sharp and hard with a hardness of 8-9 Mohs scale of mineral hardness. It is suitable for surface preparation and treatment and can be used severally hence economical.

Fly ash

which is a coal-burning by-product is found to have a Mohs hardness between 6 and 7. Even though it is cheaper than other explosives, especially for open blasting in oil and shipyard industries, it has environmental implications in case it is not well controlled.

Recycled glass beads

are used in crushed glass grit which is 5-6 on the Mohs hardness scale. It is a non-toxic medium that is used in the removal of coatings and contaminants on various surfaces. It can also be utilized in wet blasting applications.

Sodium bicarbonate

also known as baking soda has a low hardness of about 2. 5. It is especially effective in de-rusting of metals without damaging the metal surface in the process. It’s normally done at a much lower pressure and this is normally done at 20 psi while sandblasting is normally done at 70 to 120 psi.

Steel grit and steel shot

are quite durable with hardness ranging from 40-65 HRC. These abrasives are ideal for surface preparation activities as they can deliver fast stripping and cleaning.

Staurolite

ranks 7 in the Mohs scale and is made up of iron silicate and sand. It is useful for the removal of light rust or coating and is widely used in steel construction and tower erection.

Apart from these options, many other abrasives are on the market today. Silicon carbide and natural products such as walnut shells and corn cobs are also employed in certain applications. Some areas still employ sand for blasting but due to its hazardous impacts on health and is therefore discouraged due to the dangers it poses.

Coatings and Their Impact on Abrasive Selection

The nature of the coating or contamination on the surface significantly determines the abrasive media to be used and its blasting efficiency. Some of the more typical layers, found are rust, paint, mill scale, epoxy, zinc plating, rubber, and oil. Moreover, it’s important to note that with smaller particles the blasting process is more difficult. For instance, some of the powder coatings can be removed more easily than others; polymer corrosion inhibitors, on the other hand, can become quite tenacious as soon as they are exposed to air. Coatings that are blasted off in pieces may not be properly abraded.

Safety Considerations in Abrasive/Sandblasting

Here are the safety precautions while sandblasting:

Electrical Hazards

They must be located not less than fifty feet from the blasting area unless the equipment is constructed in a hazardous location. Electrical accidents are the leading cause of death, hence they need proper grounding. OSHA standards have to be followed when constructing installations.

Gas and Vapor Risks

Abrasive blasting also releases other dangerous gases including silica dust and fly ash which are very dangerous to the respiratory system. For any worker to be at the site they should put on a respirator particularly an air-purifying respirator besides other PPEs including eye protection.

Training and Vigilance

All the working protocols need to be well explained to the workers. Also, through training, all the people are aware of the risks that may exist within the workplace. It is very important to be constantly vigilant with the environment as any form of distraction can result in an accident.

Containment and Cleanup

Proper handling of debris before, during, and after sandblasting is very important in minimizing health hazards. As much as possible, one has to contain the dangerous particles because they can spread all over the place. Build a containment with the use of tents, plastic sheeting, or tarps with a height of at least six feet. The material used in the construction of this equipment also reduces dust exposure to the surrounding environment. When it comes to tips for cleaning up, it is helpful to also refer to the use of visuals such as videos.

Conclusion

To conclude, sandblasting is an effective technique for surface cleaning and preparation. It strips off rust, paint, and dirt and makes the surface come out clean and smooth for use. Sandblasting is adopted in various fields such as construction, automobile, and metal fabrication among others. There are various types of abrasives, one can use depending on the intended job. One has to be very careful not to sustain an injury hence one has to adhere to safety measures. Even though sandblasting is a traditional method, the advancement in technology makes the process more efficient and accurate. Contact us for more information.

FAQ’s

Q1. Who can sandblast my small project?

Many local businesses are involved in Dustless Blasting services. To access the Dustless Blasting services, one can search with the keywords “Dustless Blasting near me”.

Q2. Is sandblasting safe?

Conventional sandblasting may have some effects on the health of the operators and the environment, while Dustless Blasting uses safer techniques and media.

Q3. Is corrosion/rust removable by sandblasting?

Indeed, sandblasting is a very efficient technique to remove rust and it can deal with several unwanted coatings.

Q4. Under what conditions should I prefer wet blasting rather than dry blasting?

Dry blasting is useful when blasting areas that are hard to reach while wet blasting is appropriate in delicate areas.

Q5. Isn’t sandblasting done using sand?

Contemporary approaches employ sand of a different kind, such as crushed glass or organic one, thus, excluding the health concerns that come with traditional sand. 

Q6. What about the nozzle is it necessary to use a special nozzle for sandblasting?

It is important to choose the correct nozzle for the proper work of the device. Make sure that your air compressor will be able to deliver enough pressure for the given nozzle type.