What are the composition and function of 3PE anti-corrosion layer?
The structure of 3PE is epoxy powder (bottom layer) + adhesive (middle layer) + polyethylene (surface layer), with a total thickness of ≥2.5mm. Epoxy powder provides cathodic stripping protection (adhesion ≥50N/cm), and polyethylene resists mechanical damage. This technology can extend the life of the pipeline to 30 years. The cost is 20% higher than that of single-layer FBE, but the cost performance is better.
Why is double-layer FBE used for submarine pipeline anti-corrosion?
Double-layer fusion-bonded epoxy (FBE) includes anti-rust primer and impact-resistant topcoat, with a total thickness of 500-1000μm. Its seawater permeability resistance is better than 3PE, and it is easy to repair. With aluminum sacrificial anode (one group every 200 meters), the protection current density needs to be ≥110mA/m².
How to choose anti-corrosion coating in high temperature environment?
When the temperature is greater than 80℃, 3PE will be delaminated, and polyurethane foam (PUF) or glass flake coating will be used instead. Zinc silicate coating (temperature resistance 400℃) is commonly used in refinery pipelines. Before spraying, sandblasting is required to Sa2.5 level, and the anchor pattern depth is 50-75μm.
Synergistic effect of cathodic protection and anti-corrosion coating?
The coating reduces the cathodic protection current requirement by 90%, but the defects still require -0.85V (CSE) potential protection. The forced current system uses MMO/Ti anode, and the output current is ≤30A. CIPS needs to be used regularly to detect the uniformity of the potential to avoid over-protection and coating peeling.
How to detect the aging of the anti-corrosion layer of the laid pipeline?
The DCVG (direct current voltage gradient) method is used to locate the coating damage point with an accuracy of ±0.3m. Infrared thermal imaging can detect delamination defects. Laboratory sampling is carried out for salt spray resistance test (5000 hours) and bending resistance test (radius of curvature ≥25D).
