Welded steel pipe, also known as spiral welded pipe, is a steel pipe made by welding steel plates or strips after curling and forming. Welded steel pipe has a simple production process, high production efficiency, many varieties and specifications, and low equipment investment, but its general strength is lower than that of seamless steel pipe. The maximum diameter of spiral steel pipe is currently produced to 4020mm.
Due to the limitations of the manufacturing process, the diameter of the spiral pipe cannot be increased indefinitely. The maximum diameter of the spiral pipe can reach 4020mm. As the diameter increases, the thickness of the steel pipe will also increase accordingly to withstand greater pressure and provide stronger support. Therefore, a balance needs to be achieved between the length and diameter of the spiral pipe.

Cathode flat steel is a high alloy steel, which is usually made of high conductivity and corrosion resistance to ensure stability and efficiency during the electrolysis process.

‌Cathode flat steel is a flat-shaped steel made of high-quality steel. Compared with traditional steel, the characteristics of cathode flat steel:
High strength: The cathode flat steel has been treated with a special process and has high tensile strength and bending strength, and can withstand greater loads.
Corrosion resistance: The cathode flat steel has been treated with cathodic protection and coated with a corrosion-resistant coating on the surface, which can be used for a long time in harsh environments without corrosion.
Lightweight and efficient: Due to the design of the flat steel, the cathode flat steel is lighter in weight, and the installation is more convenient and efficient.
Environmental protection and energy saving: The energy required to manufacture cathode flat steel is relatively small, and resource waste can be reduced through recycling and reuse, which is in line with modern environmental protection concepts.

1. Hot-dip galvanizing: also called hot-dip galvanizing and hot-dip galvanizing is an effective way to prevent metal corrosion. It melts the zinc ingot at high temperature, puts in some auxiliary materials, and then immerses the metal structure in the galvanizing tank to make a layer of zinc adhere to the metal component, thereby achieving the purpose of corrosion protection. The advantage of hot-dip galvanizing is that it has strong anti-corrosion ability, and the adhesion and hardness of the galvanized layer are good, thus achieving the purpose of corrosion protection.

Cold galvanizing: It is electrogalvanizing, with a small amount of zinc, only 10-50g/m2, which is a process of using electrolysis to make a metal film adhere to the surface of metal or other material parts. The process of forming a uniform, dense, and well-bonded metal layer can prevent corrosion, improve wear resistance, conductivity, reflectivity, and enhance beauty.

2. Different reaction methods
Hot-dip galvanizing is a chemical treatment that belongs to an electrochemical reaction. Hot-dip galvanizing pipes react molten metal with the iron matrix to produce an alloy layer, thereby combining the matrix and the coating.

Cold galvanizing is a physical treatment, which is just brushing a layer of zinc on the surface, so the zinc layer is easy to fall off. Hot-dip galvanizing is mostly used in construction.

3. Different processes
Hot-dip galvanizing involves degreasing, pickling, soaking, dry the workpiece, immersing it in the dissolved zinc liquid for a certain period, and then taking it out.

Cold galvanizing is to use electrolytic equipment to put the workpiece into a solution composed of zinc salt after degreasing and pickling, and connect it to the negative electrode of the electrolytic equipment; place a zinc plate opposite the workpiece and connect it to the positive electrode of the electrolytic equipment, turn on the power supply, and use the directional movement of the current from the positive electrode to the negative electrode to deposit a layer of zinc on the workpiece.

Hot-dip galvanized square tubes emit fewer pollutants, mainly waste acid from pickling workpieces.

The pollutants of cold galvanizing mainly include waste acid from pickling workpieces, electroplating waste liquid, waste passivation liquid, etc. The types and quantities of emissions are much greater than hot-dip galvanizing.