We Super Steel Manufacturing Co.,Ltd(SMC) are amongst the top manufacturers and suppliers for the seamless steel pipe, welded steel pipe, OCTG products and fittings from China. We have been manufacturing and supplying these products to the industry since 1993, and received repeat orders and appreciation from our valued customers.
High quality piping products from approved manufacturers.
In order to continuously improve our offerings to our clients, we have consistently improved and upgraded our manufacturing facility and can hence offer material with stringent requirements.
Over the years, Super Steel Manufacturing Co.,Ltd(SMC) has developed an enviable reputation for project management for the Oil & Gas, Construction, Power Energy, Marine & Offshore, Water Treatment, Exploration & Drilling Services, Pipeline & Petrochemical and other heavy industries.
The many years of experience that we have means that there is always someone who has the ability to carry a project forward.
Always up to date. In this column you can find the steel pipe related articles, including industry trends, product standards and materials, and some technical guidelines.
A seamless square tube is a steel tube with a square cross-section, produced by cold drawing, extrusion, and other forming processes from a seamless round tube. It combines the high strength and pressure resistance of seamless tubes with the excellent structural stability of square tubes. Compared with welded square tubes, seamless square tubes feature smoother inner and outer surfaces, no weld defects, and superior corrosion and pressure resistance.
Because of these advantages, they are widely used in machinery manufacturing, building structures, automobile frames, and precision equipment.
However, during transportation and storage, seamless square tubes are prone to oxidation and rust due to moisture exposure. This not only affects their appearance but also compromises subsequent coating or surface protection. Therefore, rust removal and prevention are essential steps in both production and application.
1. Cleaning — The Basic Pretreatment
Cleaning is the first step before rust removal. It primarily uses solvents or emulsions to eliminate surface contaminants.
For tubes contaminated with oil, grease, or machining residues, professional solvents or emulsifying agents can effectively dissolve and remove these organic materials through wiping or soaking.
However, cleaning alone cannot remove rust, oxide scale, or welding slag. Thus, it serves mainly as an auxiliary process, preparing the surface for more effective mechanical or chemical rust removal methods.
2. Tool Rust Removal — Manual and Mechanical Methods
Tool rust removal is a commonly used method for seamless square tubes, including both manual and power-assisted techniques:
Manual Rust Removal:
Uses wire brushes, scrapers, or sandpaper to mechanically remove rust, oxide scale, and slag. It is suitable for irregular surfaces and narrow spaces, offering flexibility but low efficiency and high labor intensity. The result usually meets the Sa2 surface cleanliness standard.
Power Tool Rust Removal:
Employs electric or pneumatic grinders for faster, more uniform cleaning. It can achieve Sa3 standards, giving the surface a bright metallic luster. However, if the oxide layer is strongly adhered, even mechanical tools may struggle to achieve full removal, which can affect later coating adhesion.
3. Pickling and Passivation — Chemical Treatment
Pickling and passivation typically use chemical or electrolytic methods to remove rust, scale, and old coatings.
In steel pipe manufacturing, chemical pickling is more common — it uses acid solutions to clean the surface, sometimes followed by passivation, which forms a thin protective film to delay future corrosion.
This method can achieve a clean and smooth surface with mild roughness, but its anchor pattern depth is limited, and it can cause environmental pollution if waste acid is not properly treated. For best results, it is often combined with mechanical blasting as a subsequent step.
4. Spray (Blast) Rust Removal — High-Efficiency Mechanical Cleaning
Spray blasting (also known as shot blasting) is a highly efficient and widely adopted rust removal technique for seamless square tubes.
It works by using a high-power motor to rotate a blasting wheel, propelling abrasives such as steel shot, grit, or mineral particles at high velocity onto the tube surface under centrifugal force.
Advantages:
Thoroughly removes rust, scale, and contaminants.
Produces a uniform surface roughness (typically 40–100 μm), enhancing the mechanical adhesion between coatings and the tube surface.
Can be adjusted for inner or outer surface treatment, depending on process needs — shot blasting for internal surfaces and sand blasting for external ones.
Conclusion
The rust removal method for seamless square tubes should be selected based on service conditions, processing requirements, and the intended anti-corrosion process.
Scientific and appropriate surface treatment not only improves surface quality and coating adhesion, but also extends service life and ensures stable, reliable performance of seamless square tubes in demanding applications.
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