API 5L X52 3PE coated pipe consists of a three-layer structure, including a bottom layer of epoxy resin, an intermediate layer of adhesive and a surface layer of polyethylene, with good corrosion resistance and mechanical properties. Its process flow is as follows:
Surface treatment:
Rust removal: The surface of the steel pipe is thoroughly rust-removed, usually by shot blasting, to remove rust, scale, oil and other impurities on the surface of the steel pipe, so that the surface of the steel pipe reaches a certain degree of cleanliness and roughness to ensure that the coating can be firmly attached to the surface of the steel pipe. The quality of rust removal should meet the requirements of relevant standards, and is generally required to reach the Swedish rust removal standard Sa2.5 or above.
Preheating: The steel pipe after rust removal needs to be preheated by medium frequency, and the steel pipe is heated to a certain temperature, usually around 150℃-200℃, to remove moisture and moisture from the surface of the steel pipe, while improving the adhesion of the coating.
Coating:
Epoxy powder spraying: First, spray a layer of epoxy powder on the surface of the preheated steel pipe. The thickness of the epoxy powder is generally greater than 100μm. Epoxy powder has good adhesion, corrosion resistance and insulation properties, and can provide the first layer of anti-corrosion protection for the steel pipe.
Adhesive coating: Apply a layer of adhesive on the epoxy powder layer. The thickness of the adhesive is usually between 170-250μm. The function of the adhesive is to firmly bond the epoxy powder layer and the polyethylene layer together to form an integral anti-corrosion layer.
Polyethylene layer coating: Coat a polyethylene layer on the adhesive layer. The thickness of the polyethylene layer is generally between 2.5-3.7mm. Polyethylene has good corrosion resistance, water resistance and anti-aging properties, and can provide long-term anti-corrosion protection for steel pipes.
Molding and curing:
Molding: Depending on the processing method, the polyethylene layer can be tightly coated on the surface of the steel pipe by winding or round die coating. The winding type is divided into upper winding and lower winding; in the round mold wrapping type, negative pressure wrapping can better solve the problem of voids on both sides of the weld.
Curing: The coated steel pipe is cured to fully cure the epoxy powder, adhesive and polyethylene in the coating to form a strong and stable anti-corrosion layer. The curing temperature and time should be strictly controlled according to the characteristics of the coating material and the process requirements.
3PE Coating steel pipe
