Anti corrosion treatment method for water steel pipes

1、 Anti corrosion process of steel pipes for water use

1. Cleaning uses solvents and emulsions to clean the surface of steel to remove oil, grease, dust, lubricants, and similar organic matter. However, it cannot remove rust, oxide scale, welding flux, etc. on the surface of steel, so it is only used as an auxiliary means in anti-corrosion production. 2. Tool rust removal mainly uses tools such as wire brushes to polish the surface of steel, which can remove loose or raised oxide scales, rust, welding slag, etc. The manual anti-corrosion steel pipe treatment method can achieve Sa2 level and power.

With the continuous development of our country's economy and the vigorous development of the energy industry, long-distance oil and gas pipelines are an important way to ensure energy security. In the anti-corrosion construction process of oil (gas) pipelines, the treatment method of anti-corrosion steel pipes is one of the key factors determining the service life of pipeline anti-corrosion. It is a prerequisite for whether the anti-corrosion layer can be firmly combined with the steel pipe.

Therefore, it is necessary to strictly follow the requirements of anti-corrosion coating specifications for the surface of steel pipes, constantly explore and summarize, and continuously improve the treatment methods of anti-corrosion steel pipes.

1. Cleaning uses solvents and emulsions to clean the surface of steel to remove oil, grease, dust, lubricants, and similar organic matter. However, it cannot remove rust, oxide scale, welding flux, etc. on the surface of steel, so it is only used as an auxiliary means in anti-corrosion production.

2. Tool rust removal mainly uses tools such as wire brushes to polish the surface of steel, which can remove loose or raised oxide scales, rust, welding slag, etc.

The manual anti-corrosion treatment method for spiral steel pipes can reach Sa2 level, and the rust removal of power tools can reach Sa3 level. If there is a firm oxide scale attached to the surface of the steel, the rust removal effect of the tool is not ideal, and the anchor depth required for anti-corrosion construction cannot be achieved.

3. Acid washing is generally carried out using two methods: chemical and electrolytic methods. Chemical acid washing is only used for pipeline anti-corrosion, which can remove oxide scale, rust, and old coatings. Sometimes it can be used as a post-treatment after sandblasting and rust removal.

Although chemical cleaning can achieve a certain level of cleanliness and roughness on the surface, its anchor pattern is shallow and it is prone to environmental pollution.

4. Spray (polishing) rust removal is achieved by using a high-power motor to drive the spray (polishing) blades to rotate at high speed, causing abrasives such as steel sand, steel shot, iron wire segments, and minerals to spray (polish) the surface of steel pipes under centrifugal force. The treatment method for anti-corrosion steel pipes not only thoroughly removes rust, oxides, and dirt, but also achieves the required uniform roughness under the strong impact and friction of abrasives. After spraying (throwing) rust removal, it can not only expand the physical adsorption effect on the surface of the pipe, but also enhance the mechanical adhesion between the anti-corrosion layer and the surface of the pipe. Therefore, the treatment method of spiral steel pipe anti-corrosion steel pipe is the ideal rust removal method for pipeline anti-corrosion.

2、 Performance of Spiral Steel Pipe for Water Use

If the gap is too small, it will cause an increase in proximity effect, excessive welding heat, and result in weld burnout; Or the weld seam may form deep pits after being squeezed or rolled, affecting the surface quality of the weld seam. After the two edges of the billet are heated to the welding temperature, they form a common metal grain that penetrates and crystallizes with each other under the pressure of the extrusion roller, ultimately forming a strong weld seam. If the squeezing force is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracking will occur after being subjected to force; If the squeezing force is too high, it will cause the molten state.

The spiral steel pipe is used to feed the strip steel into the welded pipe unit, and after multiple rolling rolls, the strip steel gradually rolls up to form a circular billet with open gaps. The pressing amount of the extrusion roll is adjusted to control the weld seam gap at 1-3mm and make the two ends of the weld seam flush. If the gap is too large, it will cause a reduction in proximity effect, insufficient eddy current heat, poor intergranular bonding in the weld seam, and result in incomplete fusion or cracking. If the gap is too small, it will cause an increase in proximity effect, excessive welding heat, and result in weld burnout; Or the weld seam may form deep pits after being squeezed or rolled, affecting the surface quality of the weld seam. After the two edges of the billet are heated to the welding temperature, they form a common metal grain that penetrates and crystallizes with each other under the pressure of the extrusion roller, ultimately forming a strong weld seam.

If the extrusion force of the spiral steel pipe is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracking will occur after being subjected to force; If the extrusion force is too high, the molten metal will be squeezed out of the weld seam, which not only reduces the strength of the weld seam, but also produces a large number of internal and external burrs, and even causes defects such as welding overlap.