Let’s talk about common surface treatment methods

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During processing, transportation, storage, and other operations, the surface of workpieces often contains oxide scale, rust, molding sand residue from casting, welding slag, dust, as well as oil and other contaminants. To ensure that the coating adheres firmly to the surface of the workpiece, it is necessary to clean the surface of the workpiece before painting. Otherwise, not only will the adhesion between the coating and the base metal as well as its corrosion resistance be affected, but the base metal will also continue to corrode even under the protection of the coating, leading to peeling of the coating and impacting the mechanical properties and service life of the workpiece. Therefore, surface treatment of the workpiece before painting is an important guarantee and measure to obtain a high-quality protective layer and extend the product’s service life. Common surface treatment methods: Manual methods, such as scrapers, wire brushes, or grinding wheels. Rust and scale on the surface of the workpiece can be removed manually, but this method requires a lot of effort, results in low production efficiency, poor quality, and incomplete cleaning. Chemical treatment: It primarily involves using acidic or alkaline solutions to undergo chemical reactions with the oxides and oils on the surface of the workpiece, causing them to dissolve in those acidic or alkaline solutions. This approach is used to remove rust, oxide layers, and oils from the surface of the workpiece. Chemical treatment is suitable for cleaning thin sheet metal, but its drawback is that if the timing is not controlled properly, even with the use of corrosion inhibitors, excessive corrosion can occur in the steel. For more complex structural components and porous parts, after pickling with acidic solutions, the residual acid trapped in gaps or holes is difficult to remove completely. If not handled properly, this can become a source of corrosion for the parts in the future. Moreover, these chemicals are volatile, the treatment process is costly, and it is difficult to manage the chemical waste generated as a result. Improper handling can cause serious environmental pollution. As environmental awareness grows among people, this treatment method is being replaced by mechanical treatment methods. Mechanical treatment methods: mainly include shot blasting and blast cleaning. Shot blasting cleaning is a method that uses centrifugal force to accelerate projectiles, which are then projected at the workpiece to remove rust and clean it. However, shot blasting has poor flexibility and is limited by the available space; it can be somewhat indiscriminate when cleaning workpieces, and dead corners on the inner surfaces of the workpieces are likely to remain uncleaned. The equipment has a complex structure with many vulnerable components; in particular, parts such as blades wear out quickly, resulting in high maintenance costs, long repair times, and substantial upfront investment. Shot blasting is further divided into shot blasting and sandblasting (copper ore sand, quartz sand, emery, iron sand, sea sand). Surface treatment is carried out using shot blasting, which offers high impact force and significant cleaning efficiency. However, treating thin sheet materials with shot blasting can easily cause deformation of the materials. When the steel shots strike the surface of the material (whether through blast cleaning or shot blasting), it leads to deformation of the metal substrate. Since Fe304 and Fe203 lack plasticity, they break apart and peel off, while the oil film deforms along with the substrate; therefore, for materials contaminated with oil, blast cleaning or shot blasting cannot completely remove the oil. Among the existing surface treatment methods for workpieces, sandblasting offers the best cleaning results. Sandblasting is suitable for cleaning workpiece surfaces that require a high level of cleanliness.