The surface anti-corrosion layer of the plastic-coated and galvanized steel pipe is mainly composed of two parts: the inner plastic coating and the outer galvanized layer. These components each have different anti-corrosion properties, but they work together to enhance the corrosion resistance of the steel pipe.

1. Inner Plastic Coating
The inner plastic coating is typically applied using hot extrusion or chemical coating techniques to coat the interior of the steel pipe with thermoplastics such as polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP). The plastic coating's primary function is to isolate the steel pipe from direct contact with the internal media, preventing the penetration of corrosive media such as moisture and oxygen, thereby reducing the generation of corrosion sources.

2. Outer Galvanized Coating
The outer zinc coating is typically applied using a hot-dip galvanizing process, where the steel pipe is immersed in molten zinc to form a uniform zinc layer. This zinc layer offers excellent adhesion and corrosion resistance, shielding the steel pipe substrate from corrosive media in the environment. Zinc also has self-repairing capabilities. When microcracks appear in the coating, zinc will react with oxygen and water in the environment to form a stable zinc oxide protective layer, thereby extending the service life of the steel pipe.

Channel steel is divided into ordinary channel steel and lightweight channel steel. Hot-rolled ordinary channel steel has specifications ranging from 5# to 40#. Hot-rolled variable channel steel, supplied by mutual agreement between the supplier and the buyer, has specifications ranging from 6.5# to 30#. Channel steel is primarily used in building structures, vehicle manufacturing, other industrial structures, and fixed cabinets. Channel steel is often used in conjunction with I-beams.

Channel steel can be divided into four types based on shape: cold-formed equal-leg channels, cold-formed unequal-leg channels, cold-formed inner-flange channels, and cold-formed outer-flange channels. According to steel structure theory, the channel flanges should bear the load, meaning the channel should stand upright, not flat.

Channel Steel Specifications

Channel steel specifications are primarily expressed in terms of height (h), leg width (b), and waist thickness (d). Currently, domestic channel steel specifications range from 5# to 40#, corresponding to heights of 5 to 40cm.
At the same height, lightweight channels have narrower legs, thinner waists, and are lighter than standard channels. Channels ranging from 18 to 40 are considered large, while channels ranging from 5 to 16 are considered medium. Imported channels are marked with the actual dimensions and relevant standards. Import and export orders for channels are generally based on the required specifications after determining the corresponding carbon steel (or low-alloy steel) grade. Aside from the specification number, channels do not have specific composition or performance series.

Different properties
1. High-frequency welded steel pipe: After hot-rolled coil is formed in a forming machine, the skin effect and proximity effect of high-frequency current are used to heat and melt the edges of the tube. Pressure welding is then performed under the action of squeeze rollers to produce the product.
2. Straight seam welded steel pipe: including double-sided submerged arc welded straight seam welded steel pipe and high-frequency resistance welding. The English abbreviation of high-frequency resistance welding is ERW. Submerged arc welded straight seam steel pipe is divided into UOE, RBE, and JCOE steel pipe according to its different forming methods.

Different Materials
1. High-Frequency Welded Steel Pipe: High-frequency resistance welded steel pipe uses a different welding process than conventional welded pipe. The weld seam is formed by melting the base metal of the steel strip, resulting in greater mechanical strength than conventional welded pipe.
2. Straight seam welded steel pipe: The materials of straight seam welded steel pipe mainly include Q195, Q215, Q345, and X42 pipeline steel series. According to the specified wall thickness, straight seam welded steel pipes are divided into ordinary steel pipes and thickened steel pipes. According to the form of the pipe ends, steel pipes are divided into threaded and non-threaded types.

Different Features
1. High-frequency welded steel pipe: Smooth surface, high precision, low cost, and minimal weld height, making it suitable for 3PE anti-corrosion coating. High-Frequency Welded Steel Pipes differ significantly from Submerged Arc Welded Pipes in welding methods. Since welding is completed instantly at high speed, the difficulty of ensuring welding quality is much higher than that of submerged arc welding.
2. Straight seam welded steel pipe: The length of straight seam welded steel pipe is mainly divided into fixed length and variable length, which is mainly based on customer requirements. The length is generally 6-14 meters. Large-diameter straight seam welded steel pipe may require two steel plates for rolling, which also forms a double weld.