Surface treatment of cs seamless pipe

Proper surface treatment is crucial for enhancing the durability and performance of carbon steel seamless pipes, particularly in preventing corrosion. Below are some common methods used for surface treatment.

Tool Rust Removal:
Steel brushes and similar tools are used to polish the steel surface, effectively removing loose rust, oxide layers, and welding slag. Manual methods can achieve an Sa2 level, while power tools can reach Sa3. However, if rust is firmly attached, this method may not meet the depth requirements for corrosion prevention.

Cleaning:
Solvents and emulsions are used to clean the steel surface, removing oil, grease, and other organic contaminants. However, this method cannot remove rust or oxides and is typically used as a supplementary step in anti-corrosion processes.

Pickling:
Chemical pickling is often used to remove rust, oxide layers, and old coatings from the steel surface. Although this method can achieve a certain level of cleanliness and roughness, the resulting anchor pattern may be shallow, and it can cause environmental pollution.

Spray (Throw) Rust Removal:
In this process, steel grit or shot is propelled onto the pipe surface using high-powered motors. This method not only removes rust and contaminants but also enhances the surface roughness, improving the adhesion of anti-corrosion coatings. Spray (throw) rust removal is generally used for internal and external pipe surfaces, depending on the specific application. Key aspects to consider include:

- Rust Removal Grade:
For epoxy, ethylene, and phenolic coatings, the steel surface typically needs to reach a near-white grade (Sa2.5), ensuring adequate adhesion and achieving the desired anchor pattern depth of 40-100μm.

- Abrasive Selection:
The choice of abrasive—typically a mixture of steel grit and shot—depends on the steel's hardness, degree of rust, and required surface roughness. The mixture provides both surface strengthening and etching effects.

- Particle Size and Ratio:
The size and proportion of the abrasive particles are critical to achieving uniform cleanliness and roughness. A balance must be struck to avoid making the anti-corrosion layer too thin or prone to bubbles. The optimal ratio usually involves steel shot sizes of 0.8-1.3mm and steel grit sizes of 0.4-1.0mm, with a sand-to-shot ratio of 5-8.

Regular sampling and adjustment of the abrasive mixture during operation are necessary to maintain effectiveness, especially given the varying wear rates between steel grit and shot.