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2025Industrial sandblasting: how to prevent paint defects
Industrial abrasive treatment: the key process for removing impurities and contamination
More than 75 percent of industrial coating defects occur because of sloppily performed surface preparation. Using the wrong methods can in fact compromise the outcome of the finish, producing coatings that are uneven, poorly adhered and tend to discolor or flake over time.
Neglecting variables such as raw material, intended use of components, environmental conditions and the mechanical stresses, means increasing the risk of rework.
Surface pretreatments are therefore an essential part of any project. Industrial sandblasting, for example, used in liquid and powder coating processes, is a key process for removing surface impurities and contamination, improving paint adhesion and finish durability.
In Eurotherm plants, proper sandblasting management reduces waste, optimizes energy consumption, and enables the highest quality workmanship. In this article, Davide Quartana, a Eurotherm Process Engineer with more than 15 years of experience in blasting and painting plant design, shares some best practices for preventing finishing defects and ensuring high quality standards.
Blasting booths and systems: techniques and machinery for lasting results
Industrial sandblasting finds cross-application in numerous production sectors: from the processing of ferrous and nonferrous metals to the plastics industry, and the treatment of materials as diverse as special high-hardness alloys, or-with dedicated modes and low pressures-even softer materials such as plastic or wood.
Although based on a seemingly simple principle, the process is characterized by high operational complexity. For this reason, it requires the use of skilled personnel in handling parts, managing the sling bars, and reducing waste through the use of abrasive recovery systems.
Professional workmanship requires industrial blasting equipment that conforms to booths designed to efficiently contain dust. The process is handled by a wide range of machines-from large air blasting machines, manual blasting booths, which allow full control over how the work is performed, to automatic blasting booths, sized and configured according to production volumes and the operator’s needs.
Shot peening, blasting, sandblasting: what they are and which one to choose
The operating principle of industrial blasting machines and blast booths is simple. Steel grit is propelled at high speed by air produced by a compressor or by acceleration produced by a centrifugal turbine. The abrasive material is forcefully projected onto the surface, and the impact removes rust, scale and previous coatings, creating a textured finish.
The impact of abrasives generates a surface profile characterized by microscopic peaks and troughs that improve the mechanical adhesion of coatings, enhancing coating adhesion and increasing durability. The abrasive material can be recycled through automatic grit recovery systems, reducing consumption and ensuring maximum cost efficiency.
In Eurotherm plants for the rail industry, for example, automatic cabins with total grit recovery can reduce abrasive consumption by up to 30 percent and increase production efficiency in continuous lines.
Although similar to each other, each blasting machine is custom-designed for specific industrial applications-from booths for small components such as gears, to hanger blasters for heavy and irregularly shaped components, to blast tunnels for continuous production lines and large-scale operations. Identifying the most suitable technology depends on the raw material and factors such as production volumes and the intended use of the components.
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Sandblasting or sand blasting, performed with sharp abrasives such as steel grit, corundum or aluminum oxide, is indicated on particularly rough or defective surfaces. The use of silica sand, historically widespread, is now banned in several European countries because of health risks to operators.
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Classical blasting uses angular metal grits and is used for intensive cleaning and preparation of metal surfaces. Different is bead blasting, which uses glass, ceramic or plastic microspheres and is suitable for more delicate materials or to achieve satin finishes.
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Shot peening or shot peening with glass, ceramic or steel microspheres allows for uniform finishes and, in the automotive and aerospace industries, is used to increase the fatigue strength of components.
The choice between blasting, shot blasting, and shot peening is never standardized and may require the evaluation and guidance of qualified technical personnel. A consultative approach and configurable facilities enable not only optimally prepared surfaces, but also longer-lasting paint cycles that meet international industry standards.
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Abrasive blasting: how to optimize grit selection
Especially in the case of metal components and ferrous materials, the sandblasting pretreatment must be able to ensure a uniform finish with microscopic peaks and troughs on the surface layer to facilitate paint penetration. The process can be
customized according to production requirements and paint plant technology
, choosing the type of grit best suited to the type of surface and treatment objective. Generally, low-to-medium hardness grits are designed for use in turbine machines, while harder, heavier grits are more suitable for air blast machines.
In fact, grit differs in shape, microstructure, hardness, and chemical composition. To ensure uniformity and safety, selection should be in accordance with the series:
- ISO 11124, which defines the technical requirements for metal abrasives used in sandblasting;
- ISO 11126, which defines specific requirements for particle size, hardness and composition;
- ISO 11127, which establishes test methods to verify the quality and absence of contaminants;
Among the major abrasives on the market, metal grit has high fatigue resistance and is designed to meet the needs of foundries, industrial manufacturing, construction, architecture, and window and door frames; in the automotive, aviation, ACE, and earthmoving industries, its use is essential to impart stability and strength to means of transportation that experience considerable pressure and forces.
Metal grits can be recycled multiple times, reducing consumption by up to 40 percent compared to nonmetal abrasives, benefiting efficiency and sustainability. In contrast, stainless steel grits are used in machining operations that do not require high stock removal, for controlled and targeted abrasion, for general cleaning operations that do not alter the integrity of the microstructure, and for reinforcement shot peening and technical surface finishing. It is important to remember that the use of silica sand is now banned in several European countries because of the risk of crystalline free silica (Legislative Decree 272/1999).
Post industrial sandblasting quality control
Post-blasting quality control is an essential step in ensuring the effectiveness of the sandblasting pretreatment and the durability of subsequent painting cycles.
The first aspect to be evaluated concerns the degree of surface cleanliness of the materialSa1, Sa2, Sa2½, Sa3) based on the removal of calamine, rust and contaminants, providing an objective basis for comparison between before and after and certification of the quality achieved through the industrial blasting process.
In parallel, the roughness of the surface profile is measured using visual comparators, micrometers or dedicated electronic instruments, according to ISO 8503, which establishes criteria for characterizing peaks and troughs created by the impact of abrasives.
In addition to aesthetic and mechanical aspects, it is essential to perform checks on the level of contamination by residual dust, oils or soluble salts, which can compromise paint adhesion. In this case, the ISO 11127 series on abrasive test methods provides useful tools to ensure compliance of the material used.
Integrating these controls into the production cycle not only reduces the risk of defects and rework, but also allows the quality of the treatment performed to be documented. In contexts where high standards are required during material preparation, such as in the automotive, rail, and aerospace industries, compliance with these standards is a must to ensure surfaces suitable for receiving high-performance coatings and to guarantee process traceability.
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From industrial sandblasting to painting: sustainable solutions for industry
Responsible management of industrial blasting is not only about the quality of surface preparation that prevents product obsolescence, but also about the environmental impact and operating costs of the entire process.
In Eurotherm’s new-generation plants, the adoption of automatic grit recovery systems allows the abrasive material to be reused several times, reducing consumption by up to 40 percent compared to conventional plants. This approach improves production efficiency, limits the amount of waste to be disposed of, and helps make the painting cycle more sustainable.
In addition to grit recycling, a key role is played by dust extraction and filtration systems, which ensure safer working environments that comply with legal requirements. In Italy, the main reference is Legislative Decree 152/2006, which regulates atmospheric emissions and requires the adoption of suitable technological solutions to limit their dispersion.
Integrating these practices into the design and operation of plants means not only meeting legal requirements, but also strengthening corporate competitiveness, improving image to partners and customers, and reducing process costs. In an industrial environment increasingly oriented on the principles of circular economy, resource efficiency and energy conservation, sustainability becomes a key element in ensuring business continuity and competitive advantage.