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.

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