Introduction
Anti-corrosion steel pipe is a core infrastructure material for long-distance fluid transportation in oil and gas, chemical and other harsh corrosive environments. It forms a dense anti-corrosion layer on the surface of steel pipe through standardized processes such as surface pretreatment and multi-layer anti-corrosion coating. Below, we focus on the 3PE anti-corrosion steel pipe production process to help you understand the whole production details and meet your purchasing needs.
Production process
The production processes of 3PE anti-corrosion steel pipes include surface pretreatment, preheating, and coating of anti-corrosion medium.
a. Surface Pretreatment
Shot blasting/sand blasting is adopted to remove oxide scale, rust and oil on the surface of steel pipes, reaching Sa2.5-Sa3 level standard (the surface of the steel pipe should be free of visible attachments such as grease, dirt, oxide scale, rust, and paint coatings) to ensure the grip of the anti-corrosion coating. After rust removal, use compressed air to clean the dust, abrasive residue on the surface of the steel pipe. At the same time, the roughness (usually 40-100μm) of the steel pipe surface need to be adjusted to enhance the adhesion between the anti-corrosion layer and the surface of the steel pipe.
b. Medium Frequency Preheating
The steel pipe is uniformly heated to 230-250℃ by medium frequency induction heating to ensure the rapid melting and curing of epoxy powder. During the heating process, it is necessary to ensure that the steel pipe is uniformly heated to avoid local overheating or insufficient temperature.
c. Coating Of Anti-Corrosion Medium
3PE anti-corrosion coating is a three-layer structure:
The first layer is FBE epoxy powder primer, which is evenly attached to the preheated steel pipe surface by electrostatic spraying, with a thickness of 100-200μm. After curing treatment, the surface of steel pipes forms a dense anti-corrosion bottom layer.
The second layer is adhesive layer, the coating of adhesive is generally done by extrusion winding. Before coating, place the adhesive material into the extruder and heat it to a molten state. The temperature of the extruder should be adjusted according to the properties of the adhesive, generally within 200-250℃. The molten adhesive is extruded through the die of the extruder and evenly wrapped around the surface of the cured epoxy powder coating. The winding tension should be moderate, neither too high to cause deformation of the coating, nor too low to make the adhesive layer not tightly bond with the epoxy powder layer and subsequent polyethylene layer.
The third layer is polyethylene outer protective layer, which is evenly wrapped on the adhesive layer by extrusion coating, with a thickness of 2-3.5mm, forming an outer protection with wear resistance, impact resistance and soil corrosion resistance. Its service life can reach 30-50 years in harsh corrosive environments such as saline-alkali land and seabed.
Post processing and Quality Inspection
After completing the polyethylene coating, cool the 3PE anti-corrosion steel pipe to reduce its temperature to room temperature. Then, a comprehensive quality inspection is conducted on the anti-corrosion coating of the steel pipe, including visual inspection (checking for scratches, damages, bubbles, etc.), thickness testing, and adhesion testing (checking the adhesion between the anti-corrosion coating and the steel pipe through grid cutting or peeling tests). Only 3PE anti-corrosion steel pipes that have passed strict testing and are qualified can enter the finishes product warehouse.
