Rust Removal Methods for Seamless Square Tubes

Seamless square tube is a square cross-section steel tube made from seamless round tube by cold drawing, extrusion and other processes. It combines the high strength and high pressure resistance of seamless tube with the good structural performance of square tube. Compared with welded square tubes, seamless square tubes have smoother inner and outer walls, no weld defects, and stronger pressure bearing capacity and corrosion resistance. Therefore, they are widely used in machinery manufacturing, building structures, automobile frames and high-precision equipment.

However, during transportation and storage, the surface of seamless square tubes is susceptible to moisture or oxidation and rust, affecting the appearance and subsequent coating protection. Therefore, rust removal becomes a key step in production and application. What are the common methods of rust prevention?

Cleaning: Basic Pretreatment

Cleaning is the basic pretreatment step before rust removal of seamless square tubes, mainly using solvents and emulsions to clean the surface of square tubes. In actual operation, for some seamless square tubes that are contaminated with a lot of oil and dust during the machining process, using professional solvents or emulsions to wipe or soak them can effectively remove oil, grease, dust, lubricants and similar organic matter on the surface.

However, this cleaning method has limitations. It cannot remove rust, scale, welding flux and other substances on the surface of steel. Therefore, cleaning is usually only used as an auxiliary means in the anti-corrosion production of seamless square tubes to pave the way for more effective subsequent rust removal processes.

Tool rust removal

Tool rust removal is a commonly used rust removal method for seamless square tubes, which is mainly divided into manual tool rust removal and power tool rust removal. Manual rust removal uses tools such as wire brushes, scrapers, and sandpaper to remove surface rust, oxide scale, and welding slag by manual grinding or scraping. It is suitable for areas with complex shapes or narrow spaces and has strong flexibility, but low efficiency and high labor intensity. The quality of rust removal depends on the worker's experience and can generally reach Sa2 level standards.

Power tools, such as electric or pneumatic grinders, offer high efficiency and excellent surface finish, achieving Sa3 standards and imparting a uniform metallic luster to the square tube surface. However, if the surface oxide scale adheres firmly, the effectiveness of either tool will be limited, making it difficult to meet the requirements of subsequent corrosion protection processes.

Pickling and passivation

Generally, chemical and electrolytic methods are used for pickling and passivation treatment. Steel pipe corrosion protection only uses organic chemical pickling and passivation, which can remove scale, rust, and old coatings. Sometimes it can be used as a follow-up treatment after shot blasting. Although chemical water treatment can achieve a certain degree of cleanliness and surface roughness on the surface, its anchor marks are shallow and it is easy to cause environmental pollution to the natural environment.

Spray (blast) anti-rust treatment

Spray (shot) rust removal is an efficient rust removal method and is widely used in the rust removal of seamless square tubes. Its working principle is to use a high-power motor to drive the spray (projectile) blade to rotate at high speed, so that abrasives such as steel sand, steel shot, wire segment, minerals, etc. are violently sprayed (projected) onto the surface of the other pipe under the action of centrifugal force.

This rust removal method has significant advantages. It can not only completely remove all kinds of impurities, but also allow the square tube to achieve the required uniform roughness under the violent impact and friction of the abrasive. Generally, the surface roughness can reach 40-100μm, thereby greatly enhancing the mechanical adhesion between the anti-corrosion layer and the pipe surface. Generally speaking, shot blasting (sand) rust removal is mainly used for the inner surface treatment of the pipe, and shot blasting (sand) rust removal is mainly used for the outer surface treatment of the pipe. It can be flexibly selected according to the use scenario and specific needs of the square pipe.

Conclusion

Generally speaking, the rust removal method for seamless square tubes should be reasonably selected according to the use environment, processing requirements and anti-corrosion process. Scientific rust removal can not only improve the surface quality, but also effectively extend the service life of square tubes and ensure stable and reliable product performance.

Read more: Square Tubes VS Seamless Square Tubes

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