Industrial Sandblasting: Equipment, Abrasives and Applications in Surface Treatment

Sandblasting is a process that uses compressed air to propel abrasive material through a delivery line and out of a spray gun at high speed onto the surface of a substrate, achieving surface cleaning and modification through the impact and friction between the abrasive and the substrate.

Based on the form of the working medium, it can be divided into two categories: dry sandblasting and wet sandblasting (liquid sandblasting).

The key difference between the two is that wet sandblasting uses a mixture of liquid and abrasive material.

Researchers can further subdivide dry sandblasting by abrasive type into sandblasting (using mineral abrasives such as quartz sand) and shot blasting (using spherical metal abrasives).

Sandblasting is the most widely used surface treatment process in the industrial sector.

This method features easy operation, low cost and strong versatility.

It can effectively remove impurities such as burrs and scale from the surfaces of castings, control surface roughness, enhance the mechanical properties of the substrate, achieve a matte finish on metal surfaces, and provide excellent surface conditions for subsequent processes such as electroplating and painting.

It allows for precise control of the substrate’s surface roughness as needed, a technical advantage that is difficult for other surface treatment processes to match.

For most castings, sandblasting can serve as the final surface treatment step for finished products;

In many other scenarios, it functions as a pretreatment step prior to processes such as anodizing, electroplating, and laser treatment.

Sandblasting Equipment and Abrasives

• Manual Sandblasting Equipment

Open-type sandblasting machines are the simplest type of manual sandblasting equipment.

They lack an enclosed work chamber, offering minimal operational constraints, ample working space, a simple design, and a low learning curve.

However, they present challenges in abrasive recovery and cause severe dust pollution, requiring operators to take comprehensive protective measures.

1. Classification and Characteristics of Open-type Manual Sandblasting Machines

Researchers can classify manual sandblasting machines into pressure-fed and suction-fed types based on their operating principles:

Pressure-fed sandblasting machines have a dedicated pressure tank and use high-pressure gas to propel the abrasive through piping and out of the spray gun;

Suction-fed sandblasting machines use high-speed airflow to create negative pressure, drawing in the abrasive and propelling it outward.

Researchers can classify these machines into standard-pressure and high-pressure dry sandblasting machines based on operating pressure.

2. Chamber-type Dry Sandblasting Equipment for Dust Control and Abrasive Recycling

To reduce the hazards of dust and enable the recycling of abrasives, the industry has gradually adopted chamber-type sandblasting operations.

Researchers can classify these machines into standard-pressure manual, through-type, tracked, and rotary disc models, among others, based on their structural design.

Among them, the 8090A standard-pressure manual dry sandblaster (Fig. 1) is the most widely used.

3. Wet Sandblasting Technology: Principle, Application and Process Limitations

To address dust pollution at its source, China successfully developed liquid sandblasting machines in 1983 and put them into industrial use.

This equipment effectively solved the dust pollution problems associated with dry sandblasting, ensured operator safety, reduced investment in supporting dust collection equipment, and improved abrasive recovery rates.

The sand-to-water ratio is the core process parameter in wet sandblasting;

Operators set the abrasive-to-water ratio to 1:5 under normal operating conditions and can adjust this ratio as needed according to surface roughness requirements.

Liu Weidong et al. employed the liquid sandblasting process for anti-corrosion and rust removal on oil tanks.

This process eliminates the need for preliminary cleaning, improves operational efficiency, and resolves issues associated with dry sandblasting—such as excessive dust generation, rapid temperature rise on tank walls, and the tendency to generate static electricity—thereby ensuring construction safety and efficiency.

Since wet sandblasting uses water, operators must take measures to prevent re-rusting and complete subsequent processes including rust removal and drying as quickly as possible.

• Automated Sandblasting Equipment

Automation technology has advanced rapidly in the field of sandblasting equipment, and automated sandblasting operations are now widely used in areas such as rust removal from large ship hulls, on-site treatment of oil and gas pipelines and tanks, automated processing of straight and bent pipes of various specifications, and rust removal from rail transit components.

These applications involve high operational intensity, significant operational difficulty, severe dust pollution, and challenges in abrasive recovery;

The use of sandblasting robots has enabled the automation and intelligent operation of the sandblasting process.

In the 1980s, the Netherlands took the lead in researching and developing CNC shot blasting equipment, establishing a mature technological system.

In the field of ship hull derusting, some countries began research on wall-climbing sandblasting robots early on and have already developed a comprehensive technological system.

The shipyard sandblasting climbing robot developed by Faína et al. features a lightweight, compact structure, can move stably on inclined shipside surfaces, and compensates for hull surface deformations through rotation;

Souto et al. developed the unsupervised ship hull sandblasting robot, conducted multiple rounds of on-site validation for it, and successfully applied it in engineering practice.

China’s level of research and development in automated sandblasting equipment lags behind that of other countries;

High-end automated sandblasting systems and robots still rely on imports, resulting in high operating costs.

In 2004, Chinese scholars completed the development of a prototype sandblasting rust-removal robot and subsequently carried out structural optimization and process improvements tailored to rust-removal operations on large oil tanks.

Wang Changjiang et al. applied automated pipeline sandblasting equipment to large-diameter pipeline projects, addressing issues such as the difficulty of manual sandblasting operations, high labor intensity, and low efficiency, thereby ensuring processing quality and pipeline transportation safety.

Industries widely adopt the BlastMan B20 automatic sandblasting robot in the rail transit sector;

Through optimization of process parameters, it has achieved a balance between processing quality, operational efficiency, and operating costs.

Researchers have successfully industrialized PLC-controlled chain-type automatic sandblasting machines and automated wet sandblasting equipment.

Zhao Junyou and his team broke through technological blockades imposed by other countries to develop high-load, highly flexible, and environmentally friendly ship wall-climbing sandblasting and derusting equipment to meet the demands of ship hull derusting operations; the equipment is shown in Figure 2.

Bai Yufeng and colleagues applied wall-climbing robots to sandblasting of steel structures at high altitudes, reducing operational difficulty through simulation-based design and enabling the recycling of abrasive materials.

In the field of sandblasting the inner walls of pipelines, the development of automated sandblasting equipment for large-diameter straight pipes and elbows effectively reduces labor intensity, prevents quality defects caused by uneven manual sandblasting, and improves production efficiency.

• Sandblasting Abrasives

Engineers divide abrasives commonly used in industrial sandblasting into synthetic abrasives (such as ceramics, brown fused alumina, white fused alumina, and steel shot) and natural abrasives (such as garnet and quartz sand);

Recycled materials, such as air-quenched slag, can also be used as abrasives.

The selection of abrasives is primarily based on hardness, particle size, regularity of morphology, cost, and recovery rate.

Abrasives with low hardness have high wear rates, are prone to breakage, and tend to remain on the substrate surface, causing secondary contamination and generating large amounts of dust;

Abrasives with irregular morphology and uneven particle sizes are prone to forming pits and grooves of varying depths on the substrate surface, resulting in surface defects.

1. Classification and Selection Criteria for Conventional Sandblasting Abrasives

Shen Guoliang et al. reported on new types of soft abrasives, such as plastic abrasives, glass abrasives, sponge abrasives, and dry ice;

However, these abrasives have limited application conditions.

Among them, researchers have conducted more in-depth studies on sponge abrasives as an environmentally friendly abrasive.

Sponge abrasives take polyurethane sponge as the bonding matrix. Manufacturers bond abrasives of different specifications within this matrix to form a cluster-like structure, as shown in Figure 3a.

Under the action of a high-pressure air stream, when the sponge impacts the surface of the substrate, it instantly deforms and adheres to the surface, creating a vacuum.

Relying on its high adsorption capacity, it adsorbs and removes impurities such as surface dust, rust, and scale, thereby completing the surface cleaning, as shown in Figure 3b.

2. Working Principle and Structural Characteristics of Sponge Abrasives

The sponge abrasive sandblasting equipment weighs approximately 150 kg, has a small footprint, and is easy to move.

It features a four-unit independent structure, with each unit operating without interfering with the others.

The equipment provides excellent abrasive dust collection, significantly improving visibility in the work environment and facilitating post-blasting surface quality inspection;

It features a low rebound rate and simple abrasive recovery, preventing equipment damage caused by the splashing of conventional abrasives;

While the recovery rate for steel shot in conventional abrasives is approximately 80%, that of sponge abrasives can reach 96%, resulting in an extremely low loss rate.

3. Advantages and Limitations of Sponge Abrasive Sandblasting Technology

However, the sponge-wrapped structure reduces impact energy, affecting rust removal efficiency and treatment results;

At the same time, its higher cost and lower economic efficiency limit its large-scale application.

Applications of Sandblasting

• Improving the Surface Condition of the Base Material

Sandblasting can alter the macroscopic roughness of the base material’s surface, while also having a significant impact on the base material’s fatigue properties, stress distribution, crack propagation behavior, and wear resistance.

Studies have shown that sandblasting refines the grain structure of the substrate’s surface layer, increases microhardness, and converts residual tensile stress on the surface into compressive stress.

This, in turn, enhances the substrate’s surface strength, hardness, and wear resistance, suppresses the initiation of surface cracks, and significantly improves fatigue strength.

Li Mingxing et al. found that after sandblasting treatment, the A7N01 aluminum alloy exhibited reduced stress corrosion resistance, as well as decreased resistance to pitting corrosion and passivation film repair capacity.

Dong et al. found that sandblasting 304 austenitic stainless steel prior to plasma carburizing significantly improved nitriding efficiency and wear resistance, with the strengthening effect being dependent on the treatment time.

Zhu Jidong et al. performed shot peening on 26MnB5 steel and found that this treatment significantly improved the material’s tensile properties and low-cycle fatigue life.

Research by Gong Xu et al. indicates that moderate sandblasting can improve the flexural strength and crack propagation resistance of Y-TZP ceramics.

To ensure the effectiveness of sandblasting treatment and avoid surface defects and abrasive residue, process parameters such as sandblasting pressure, angle, distance, and abrasive particle size must be strictly controlled. Qu et al. investigated the effects of different process parameters on 7N01 aluminum alloy;

The results showed that abrasive particle size had the most significant impact on surface roughness and residual stress.

Residual compressive stress can extend fatigue life, whereas increased roughness shortens it.

Wang Chunshui et al. proposed a method of “multiscale analysis—optimal evaluation scale—roughness parameter characterization,” which provides a theoretical basis for the formulation and quality control of sandblasting processes.

• Promoting Substrate Surface Modification

Superhydrophobic surfaces, which originate from the lotus effect, are an important characteristic of surface wettability.

Superhydrophobic metal surfaces can enhance a substrate’s corrosion resistance, oxidation resistance, and self-cleaning capabilities, and are widely used in fields such as oil and gas transportation and aerospace.

The sandblasting process can create a micron-scale rough surface structure on the substrate, providing a critical morphological foundation for the preparation of superhydrophobic surfaces.

Zhang Hongmin et al. employed a sandblasting–acid etching–fluorocarbon resin treatment process to prepare a superhydrophobic surface on a titanium substrate;

Li Jing et al. used a sandblasting–electroplating process to prepare an unmodified micro-nano dual-scale superhydrophobic surface on a carbon steel substrate. Sandblasting–anodizing–fluorination is the mainstream process for preparing superhydrophobic surfaces.

Sandblasting creates micron-scale pits, while anodizing forms a nanoscale network structure.

This process has been successfully applied to substrates such as Ti6Al4V, aluminum alloys, and pure titanium to produce superhydrophobic surfaces with stable performance.

• Enhancing Coating Adhesion

Coatings are an important means of protecting and strengthening material surfaces;

The bond strength of coatings applied via thermal spraying, plasma spraying, and other methods directly determines their in-service performance.

Surface roughening of the substrate is a key step in improving coating bond strength.

Optimizing the sandblasting pretreatment process allows for precise control of surface roughness, thereby significantly enhancing coating adhesion.

A comparative study by Vishal et al. indicates that, compared to electrical discharge machining (EDM), sandblasting is more suitable for the pretreatment of steel substrates prior to thermal spraying of Ni-5Al coatings.

Surfaces treated by EDM contain hard carbides and austenitic phases, making it difficult to achieve good coating adhesion.

Li Baozeng et al. found that the adhesion of water-based coatings is positively correlated with substrate roughness, and increasing roughness can enhance the coating’s corrosion resistance.

Anna et al. indicated that the type of abrasive has a significant impact on the properties of steel surfaces, while process parameters have a relatively weaker influence.

Zhang Laiqi et al. found that coating bond strength follows an approximately normal distribution with respect to substrate roughness;

Excessive sandblasting pressure increases surface defects and reduces bond strength.

Ma Kangzhi et al. demonstrated that increasing abrasive particle size enhances surface roughening and coating bond strength, while decreasing particle size increases internal stress in the substrate, a phenomenon influenced by substrate hardness.

Ji Chaohui et al. significantly improved the coating bond strength on TC4 substrate surfaces by adjusting the abrasive particle size and sandblasting pressure.

Wang Jing et al. used three-dimensional surface topography parameters to evaluate coating bond strength, revealing the correlation mechanism between surface topography and bond strength, thereby providing theoretical support for the optimization of sandblasting processes.

• Improving the Bond Strength of Composite Materials

Adhesive bonding is a commonly used method for joining materials.

Compared to riveting and bolting, it preserves material integrity, avoids stress concentrations caused by drilling holes, and is suitable for materials with poor weldability.

The quality of adhesive joints is significantly influenced by surface treatment processes, and sandblasting is a key pretreatment method for enhancing adhesive strength.

Research by Liu Xiaojing et al. showed that the shear strength of adhesive joints in 5083 aluminum alloy increased after sandblasting pretreatment.

Tou Chuiqian et al. compared the effects of sandpaper grinding, sandblasting, and phosphoric acid anodizing on the adhesive performance of aluminum-lithium alloys;

Sandblasting significantly improved joint strength without noticeably affecting corrosion resistance.

Zhang Ai’ai et al. applied sandblasting and anodizing treatments to AA5083 aluminum alloy, and both processes effectively enhanced low-temperature adhesive strength.

Xu Fei et al. compared the effects of sandblasting and constant-voltage anodizing on the adhesive properties of titanium alloys;

Both processes increased bond strength, with the combined treatment yielding superior results.

The sandblasting–anodizing combined treatment process proposed by Chen Ting et al. can increase the surface roughness and polar bond content at the aluminum alloy/CFRP adhesive interface, reduce the thickness of the contamination layer, and improve the performance of the adhesive joint.

Sandblasting process parameters have a significant impact on bond strength.

Researchers have investigated the effect of aluminum oxide abrasive particle size on the adhesive strength of titanium alloys, cobalt-chromium alloys, and ceramic composites;

Jiang Tongzhu et al. used abrasive particle size, air pressure, and spray angle as variables to reveal the patterns governing the influence of aluminum alloy surface roughness on rubber-to-metal bonding strength;

Zhang Yujie et al. determined the optimal sandblasting process for different substrate materials by adjusting the sandblasting duration and evaluated the treatment effectiveness based on the tensile-shear strength of the bonded joints.

Summary

(1) The level of automation in sandblasting equipment continues to improve;

However, existing automated equipment and sandblasting robots are primarily designed for specific operating conditions, lacking versatility and struggling to meet the demands of flexible operations across multiple scenarios.

(2) Addressing sandblasting dust pollution requires a balanced approach that combines equipment improvements with abrasive innovation.

Currently, there is a lack of environmentally friendly abrasives that offer high-efficiency processing, low pollution, and cost-effectiveness;

The development of eco-friendly abrasives remains a key research area.

(3) Sandblasting enables precise control of substrate surface roughness, providing high-quality surfaces for subsequent processes;

However, the industry lacks unified and comprehensive process standards and operating procedures.

It is necessary to rely on extensive experimental data to refine the process system and achieve stable, controllable quality.