The necessity of pickling SMLS pipes

In order to improve the corrosion resistance of seamless steel pipes and prolong the service life of the products, the seamless steel pipes must be pickled and passivated to form a protective film on the surface.

First of all, we must understand what is pickling: the method of using acid solution to remove oxide scale and rust on the surface of steel is called pickling. Acids for pickling include sulfuric acid, hydrochloric acid, phosphoric acid and mixed acids.

The pickling process is to remove the surface oxide scale, and then go through lubrication treatment (carbon steel-phosphorous saponification, stainless steel-butter lime, copper and aluminum pipe-oiling), using the old process-copper plating), and then deep drawing processing. If the seamless steel pipe is not pickled, there may be oxides and oil stains on the surface, and the nuclear energy of the phosphating liquid cannot remove them, and the quality of phosphating will be reduced. Moreover, in the manufacturing process of seamless steel pipes, after many processes, if you are not careful, it will leave scars on the surface of seamless steel pipes, which will reduce the corrosion resistance of parts and directly affect the service life.

Specific Steps of the Pickling Process

The process flow for pickling seamless steel pipes typically includes the following key steps:

1. Pretreatment

Before the actual pickling process, the steel pipes undergo degreasing and cleaning to remove surface grease and other organic contaminants. This step typically uses an alkaline solution or specialized cleaning agents to ensure uniform pickling results.

2. Pickling

The steel pipes are immersed in a pre-configured pickling tank. The acid concentration, temperature, and treatment time must be precisely controlled based on the pipe material and surface condition. The hydrochloric acid solution temperature is generally controlled between room temperature and 60°C, and the treatment time ranges from a few minutes to half an hour.

3. Water Washing and Neutralization

After pickling, the steel pipes are immediately rinsed with water to remove any residual acid. A multi-stage water wash process is typically used, with a small amount of alkaline solution added in the final wash to neutralize the pH value on the pipe surface and ensure a near-neutral pH.

4. Passivation

Some pickled seamless steel pipes for high-end applications also undergo a passivation treatment, which forms an extremely thin protective film on the pipe surface to enhance corrosion resistance.

5. Drying and Rust Prevention

The final step is to dry the steel pipe and, if necessary, apply rust-proof oil or other protective agents to prevent further rust during storage and transportation.

The Necessity of Pickling Seamless Pipes

1. Pickling removes impurities such as scale, rust, and welding slag from the surface of seamless pipes, resulting in a smoother surface and improving the surface quality.

2. Pickling also removes oil and corrosive substances from the pipe surface, preventing corrosion and damage, and providing a good foundation for subsequent treatments such as galvanizing and chrome plating.

3. Pickling also improves the surface compatibility of the pipe, enhances the adhesion of the coating, and extends the service life of the seamless pipe.

Performance Advantages of Pickled Seamless Steel Pipes

Seamless steel pipes that have been pickled have the following significant advantages:

1. Excellent Surface Quality

Pickling effectively removes the oxide layer and minor defects on the steel pipe surface, resulting in a smoother and flatter surface with significantly reduced roughness. This surface quality is particularly important for subsequent secondary processing such as plating and painting.

2. High Dimensional Accuracy

The pickling process does not alter the basic dimensions of the steel pipe, but it does remove uneven surface oxide layers. This helps maintain the original manufacturing accuracy and is particularly suitable for applications requiring tight dimensional tolerances.

3. Stable Mechanical Properties

A proper pickling process does not affect the mechanical properties of the steel pipe substrate. Instead, it eliminates surface stress concentration points, helping to maintain the material's original strength characteristics.

4. Improved Corrosion Resistance

By removing surface oxides and possibly performing a passivation treatment, pickled seamless steel pipe exhibits superior short-term corrosion resistance compared to ordinary seamless steel pipe, laying a good foundation for long-term corrosion protection.

Types of Seamless Steel Pipes Requiring Pickling

Typically, stainless steel seamless pipe is the primary type of pipe requiring pickling. During production, processing, transportation, and storage, stainless steel is prone to forming a scale or rust on its surface. This rust and oxide not only affect the product's aesthetics but also reduce its corrosion resistance and service life. Therefore, pickling can remove these surface contaminants, restoring the stainless steel seamless pipe to its original metallic luster and performance.

Also, some carbon steel seamless pipes may require pickling under special circumstances. For example, when the carbon steel pipe surface is severely rusted or contaminated, pickling can help clean the surface and provide excellent conditions for subsequent treatments (such as galvanizing and painting).

Summary

Pickling passivation of seamless steel pipes is a chemical reaction to remove rust on the surface of seamless steel pipes. Pickling and passivation of stainless steel can remove all kinds of dirt, such as oil stains, rust, oxide scale, welding spots, etc. After pickling and passivation of seamless steel pipes, the surface becomes uniform silver white, which greatly improves the corrosion resistance of stainless steel and is suitable for various models. Stainless steel parts, plates and equipment. It is simple to operate, easy to use, economical and practical. At the same time, it is added with high-efficiency corrosion inhibitors and fog inhibitors to prevent metal corrosion, hydrogen embrittlement, and acid fog. It is suitable for small and complex workpieces, and is not suitable for pasting. It is superior to similar products in the market.