What are the production processes for plastic-coated steel pipes

The production processes for plastic-coated steel pipes mainly include the following key steps: raw material preparation, steel pipe pretreatment, coating treatment, curing and cooling, and quality inspection.

First, Raw Material Preparation for Plastic-Coated Steel Pipes:

The raw materials for plastic-coated steel pipes typically include seamless steel pipes, straight seam steel pipes, or spiral pipes, which must possess good mechanical properties and chemical stability.

Plastic Powder: Materials such as resin and polyethylene are selected according to the intended use of the plastic-coated steel pipe to ensure a strong bond between the coating and the steel pipe and excellent corrosion resistance.

Second, Pretreatment of Plastic-Coated Steel Pipes:

Cutting and Removing Weld Beams: Remove surface impurities and defects from the plastic-coated steel pipe, improving its surface quality.

Sandblasting and Dust Removal: Utilizes high-pressure airflow to remove rust and oil stains, enhancing coating adhesion.

Acid Pickling or Alkali Pickling: Removes the oxide and rust layers, providing a good substrate for coating treatment.

Third, Coating Treatment of Plastic-Coated Steel Pipes

Hot-dip Plastic Coating: After preheating the steel pipe, plastic powder is applied, and then the pipe is placed in a constant-temperature electric furnace to melt the powder and adhere it to the steel pipe surface.

Spray Coating: Plastic coating is sprayed onto the steel pipe surface using a spray gun to form a uniform and dense coating, suitable for small-diameter plastic-coated steel pipes.

Electrostatic Spray Coating: Utilizing the electrostatic adsorption effect, powder coating is sprayed onto the steel pipe, and then the pipe is placed in a constant-temperature oven for curing, forming a hard and wear-resistant coating.

Fourth, Curing and Cooling of Plastic-Coated Steel Pipes

Curing of Plastic-Coated Steel Pipes: Heating evaporates the solvent in the coating, making the coating hard and wear-resistant. Strict control of temperature and time is required.

Cooling of Plastic-Coated Steel Pipes: The coating temperature is lowered to room temperature to ensure that the coating does not crack or deform due to excessive temperature differences.

Fifth, Quality Inspection of Plastic-Coated Steel Pipes

Coating Thickness: Measured using a magnetic thickness gauge, inner wall thickness ≥ 0.3mm.

Adhesion: Cross-cut test (ISO 2409) shows no peeling.

Spark Test: 15kV voltage scan shows no breakdown (3.2mm coating).

Sixth, Application Areas of Plastic-Coated Steel Pipes

Plastic-coated steel pipes are widely used in water supply, drainage, fire protection, power, chemical, and other fields, especially in applications with high requirements for pipe materials, such as highways and urban underground pipe networks.