Coal Tar Epoxy Steel Pipe Coating
Coal Tar Epoxy Coating for Steel Pipes
Steel pipes are widely used in various industries, including oil and gas, water supply, and construction, due to their strength and durability. However, they are susceptible to corrosion, especially when exposed to harsh environments such as seawater, soil, and chemicals. To protect steel pipes from corrosion, a variety of coatings are used, among which coal tar epoxy coating stands out for its exceptional protective properties.
What is Coal Tar Epoxy Coating?
Coal tar epoxy is a protective coating that combines coal tar pitch and epoxy resin. This combination results in a coating with excellent adhesion, water resistance, and chemical resistance, making it ideal for protecting steel pipes in aggressive environments. The coating forms a thick, durable barrier that prevents corrosive elements from reaching the steel surface.
Coal Tar Enamel Wrapping Coating System
- Primer – chlorinated rubber and synthetic plasticized primer.
- Coal tar enamel – hot-pour coal tar enamel modified by inert mineral filler.
- Inner wrap – reinforced glass fiber mat.
- Coal tar enamel – hot-pour coal tar enamel modified by inter mineral filler.
- Outer wrap – impregnated and coal tar enamel coated reinforced glass fiber mat.
Composition
- Coal Tar Pitch: A byproduct of the coal distillation process, coal tar pitch is a viscous liquid that provides excellent water and chemical resistance.
- Epoxy Resin: A type of polymer that cures to form a hard, durable coating. Epoxy resins provide strong adhesion to the steel substrate and enhance the mechanical properties of the coating.
Properties
- Excellent Adhesion: Bonds strongly to steel surfaces, ensuring long-lasting protection.
- Water Resistance: Provides an impermeable barrier against water, preventing corrosion.
- Chemical Resistance: Resistant to a wide range of chemicals, including acids, alkalis, and solvents.
- Abrasion Resistance: Withstands mechanical wear and tear, making it suitable for buried or submerged pipelines.
- Temperature Resistance: Can withstand a wide range of temperatures, from sub-zero to high temperatures.
Application Methods
Applying coal tar epoxy coating to steel pipes involves several steps to ensure proper adhesion and performance. The common methods include:
Surface Preparation
- Cleaning: Remove dirt, grease, oil, and other contaminants from the steel surface.
- Abrasive Blasting: Use abrasive blasting to remove rust, mill scale, and old coatings, creating a rough surface profile for better adhesion.
- Inspection: Thoroughly inspect the prepared surface to ensure it is free from contaminants and has the required surface profile.
Coating Application
- Mixing: Combine the coal tar pitch and epoxy resin components according to the manufacturer’s instructions. Ensure thorough mixing to achieve a uniform coating.
- Application:
- Brush or Roller: Suitable for small areas or touch-up work.
- Spray Application: Airless spray equipment is commonly used for large surfaces, providing a uniform and consistent coating.
- Thickness Control: Apply the coating to the specified thickness, usually in multiple layers, to achieve the desired protection.
Curing
- Initial Cure: Allow the coating to dry according to the manufacturer’s guidelines. Initial curing can take several hours to a day, depending on environmental conditions.
- Final Cure: Complete curing may take several days, during which the coating achieves its full mechanical and chemical resistance properties.
Quality Control
- Inspection: Inspect the coating for uniformity, thickness, and adhesion. Use non-destructive testing methods such as dry film thickness gauges and holiday detectors.
- Repairs: Address any defects or thin areas by applying additional coats or repairing the affected sections.
Applications
Coal tar epoxy coatings are used in a variety of applications where steel pipes are exposed to harsh environments:
Oil and Gas Industry
- Buried Pipelines: Protects buried pipelines from soil and groundwater corrosion.
- Subsea Pipelines: Provides resistance to seawater and marine organisms.
- Storage Tanks: Used on the interior and exterior surfaces of storage tanks to prevent corrosion from stored products and environmental exposure.
Water Supply and Treatment
- Water Mains: Protects water mains from soil and water corrosion.
- Sewage Pipes: Provides chemical resistance to sewage and wastewater.
- Treatment Plants: Used on pipes and equipment in water and wastewater treatment plants to prevent corrosion from chemicals and treated water.
Construction Industry
- Piling and Foundation Structures: Protects steel piles and foundations used in building construction from soil and water corrosion.
- Bridges and Marine Structures: Used on steel components of bridges and marine structures to prevent corrosion from environmental exposure.
- .
Tolerance of Outside Diameter
| Standard | Out Diameter | Tolerance of Pipe End | Tolerance of Pipe Body |
| API 5L | 219.1~273.1 | +1.6mm, -0.4mm | ±0.75% |
| 274.0~320 | +2.4mm, -0.8mm | ±0.75% | |
| 323.9~457 | +2.4mm, -0.8mm | ±0.75% | |
| 508 | +2.4mm, -0.8mm | ±0.75% | |
| 559~610 | +2.4mm, -0.8mm | ±0.75% | |
| GB/T 9711-1 ISO 3183-1 |
219.1~273.1 | +1.59mm, -0.4mm | ±0.75% |
| 219.1~273.1 | 2.38mm, -0.79mm | ±0.75% | |
| 219.1~273.1 | 2.38mm, -0.79mm | ±1% | |
| 219.1~273.1 | 2.38mm, -0.79mm | ±1% | |
| GB/T 9711-2 ISO 3183-2 |
219.1~273.1 | ±0.5% | ±0.75% |
| 323.9~355.6 | ±1.6mm | ±0.75% | |
| 406.4~610 | ±1.6mm | ±3.0mm |
Tolerance of Wall Thickness
| Standard | Grade | Out Diameter | Wall Thickness | Tolerance |
| API 5L | / | 219.1~457 | 4~20 | +15%, -12.5% |
| B | 508~610 | 4~20 | +17.5%, -12.5% | |
| X42-X80 | 508~610 | 4~20 | +19.5%, -8% | |
| GB/T 9711-1 ISO 3183-1 |
– | 219.1~457 | 4~20 | +15%, -12.5% |
| L245 | 508~610 | 4~20 | +17.5mm, -10% | |
| L290-L555 | 508~610 | 4~20 | +19.5%, -8% | |
| GB/T 9711-2 ISO 3183-2 |
– | 219.1~610 | 4~20 | +1.0mm, -0.5mm |
| – | 219.1~610 | 10.1~20 | +10%, -5% |
Chemical Analysis and Mechanical Properties
| Standard | Class | Grade | Chemical Analysis(%) | Mechanical Properties | ||||
| C | Mn | P | S | Tensile Strength(Mpa) | Yield Strength(Mpa) | |||
| API 5L | PSL1 | B | 0.26 | 1.20 | 0.030 | 0.030 | ≥414 | ≥241 |
| X42 | 0.26 | 1.30 | 0.030 | 0.030 | ≥414 | ≥290 | ||
| X46 | 0.26 | 1.40 | 0.030 | 0.030 | ≥434 | ≥317 | ||
| X52 | 0.26 | 1.40 | 0.030 | 0.030 | ≥455 | ≥359 | ||
| X56 | 0.26 | 1.40 | 0.030 | 0.030 | ≥490 | ≥386 | ||
| X60 | 0.26 | 1.40 | 0.030 | 0.030 | ≥517 | ≥414 | ||
| X65 | 0.26 | 1.45 | 0.030 | 0.030 | ≥531 | ≥448 | ||
| X70 | 0.26 | 1.65 | 0.030 | 0.030 | ≥565 | ≥483 | ||
| PSL2 | B | 0.22 | 1.20 | 0.025 | 0.015 | 414-578 | 241-448 | |
| X42 | 0.22 | 1.30 | 0.025 | 0.015 | 414-578 | 290-496 | ||
| X46 | 0.22 | 1.40 | 0.025 | 0.015 | 434-758 | 317-524 | ||
| X52 | 0.22 | 1.40 | 0.025 | 0.015 | 455-758 | 359-531 | ||
| X56 | 0.22 | 1.40 | 0.025 | 0.015 | 490-758 | 386-544 | ||
| X60 | 0.22 | 1.40 | 0.025 | 0.015 | 517-758 | 414-565 | ||
| X65 | 0.22 | 1.45 | 0.025 | 0.015 | 531-758 | 448-600 | ||
| X70 | 0.22 | 1.65 | 0.025 | 0.015 | 565-758 | 483-621 | ||
| X80 | 0.22 | 1.85 | 0.025 | 0.015 | 621-827 | 552-690 | ||
| GB/T 9711-1 ISO 3183-1 |
– | L245 | 0.26 | 1.15 | 0.030 | 0.030 | ≥415 | ≥245 |
| – | L290 | 0.28 | 1.25 | 0.030 | 0.030 | ≥415 | ≥290 | |
| – | L320 | 0.30 | 1.25 | 0.030 | 0.030 | ≥435 | ≥320 | |
| – | L360 | 0.30 | 1.25 | 0.030 | 0.030 | ≥460 | ≥360 | |
| – | L390 | 0.26 | 1.35 | 0.030 | 0.030 | ≥490 | ≥390 | |
| – | L415 | 0.26 | 1.35 | 0.030 | 0.030 | ≥520 | ≥415 | |
| – | L450 | 0.26 | 1.40 | 0.030 | 0.030 | ≥535 | ≥450 | |
| – | L485 | 0.23 | 1.60 | 0.030 | 0.030 | ≥570 | ≥485 | |
| – | L555 | 0.18 | 1.80 | 0.030 | 0.030 | ≥625 | ≥555 | |
| GB/T 9711-2 ISO 3183-2 |
– | L245MB | 0.16 | 1.50 | 0.025 | 0.020 | ≥415 | 245-440 |
| – | L290MB | 0.16 | 1.50 | 0.025 | 0.020 | ≥415 | 290-440 | |
| – | L360MB | 0.16 | 1.60 | 0.025 | 0.020 | ≥460 | 360-510 | |
| – | L415MB | 0.16 | 1.60 | 0.025 | 0.020 | ≥520 | 415-565 | |
| – | L450MB | 0.16 | 1.60 | 0.025 | 0.020 | ≥535 | 450-570 | |
| – | L485MB | 0.16 | 1.70 | 0.025 | 0.020 | ≥570 | 485-605 | |
| – | L555MB | 0.16 | 1.80 | 0.025 | 0.020 | ≥625 | 555-675 | |
Advantages of Coal Tar Epoxy Coating
Long-Lasting Protection
Coal tar epoxy coatings provide long-lasting protection to steel pipes, significantly extending their service life. The coating’s durability reduces the need for frequent maintenance and replacements, resulting in cost savings over time.
Versatility
Suitable for a wide range of applications, coal tar epoxy coatings can protect steel pipes in various environments, from underground pipelines to marine structures. Their versatility makes them a preferred choice in many industries.
Cost-Effective
Compared to other protective coatings, coal tar epoxy coatings offer a cost-effective solution for corrosion protection. The initial investment in coating application is offset by the reduced maintenance and extended service life of the steel pipes.
Environmental Resistance
Coal tar epoxy coatings provide excellent resistance to environmental factors such as water, chemicals, and temperature variations. This makes them ideal for use in harsh conditions where other coatings may fail.
Safety and Environmental Considerations
While coal tar epoxy coatings offer excellent protection, it is essential to handle and apply them safely due to the potential health and environmental hazards associated with coal tar pitch.
Health Hazards
- Skin and Eye Irritation: Coal tar pitch can cause skin and eye irritation. Use personal protective equipment (PPE) such as gloves, goggles, and protective clothing during handling and application.
- Respiratory Risks: Inhalation of vapors or dust can cause respiratory issues. Use appropriate respiratory protection and ensure adequate ventilation in confined spaces.
Environmental Impact
- Disposal: Dispose of any waste materials, including unused coating and contaminated equipment, according to local regulations. Avoid releasing coal tar pitch into the environment, as it can be harmful to aquatic life.
- Spill Management: Implement spill management procedures to contain and clean up any accidental spills, preventing soil and water contamination.
Safety Precautions
- Training: Ensure all personnel involved in the application process are trained in the safe handling and application of coal tar epoxy coatings.
- Emergency Procedures: Establish emergency procedures for handling spills, exposure incidents, and other emergencies related to coating application.
Conclusion
Coal tar epoxy coatings provide a robust and durable solution for protecting steel pipes from corrosion in a variety of harsh environments. Their excellent adhesion, water resistance, and chemical resistance make them suitable for use in the oil and gas, water supply, and construction industries. Proper application and handling are essential to ensure the effectiveness and safety of these coatings. By following best practices and safety guidelines, coal tar epoxy coatings can significantly extend the service life of steel pipes, providing long-term protection and cost savings.
Corrosion prevention of pipes refers to measures to slow down or prevent corrosion and deterioration of pipes under the chemical or electrochemical action of the internal and external media or by the metabolic activities of microorganisms.
A concrete coated pipe, also known as a concrete weight coating pipe (CWC pipe), is a steel pipe that has been externally coated with concrete. The concrete coating consists of a mixture of cement, aggregates, reinforced steel mesh, and water. The purpose of this coating is to provide strong downward force protection or negative buoyancy for the pipelines. These pipes are commonly used in sub-sea (submarine) pipelines, as the concrete coating adds the necessary weight to withstand the pressure of seawater.
FBE coating steel pipe is fusion bonded epoxy coating steel pipe.It is a kind of external heat resin used for pipes.With a form of dry powder at thickness 400-600 microns on to the heated surface of pipe.Once the FBE coated on the pipe surface,the FBE film provides an extremely hard surface with great adhesion to the surface of pipe.The FBE layer in a even form and have good resistance to the chemical reaction.
Pipe Type: FBE (Fusion Bond Epoxy) Coated Pipe, Epoxy Coated Carbon Steel Pipe,Single-layer Anti-corrosion Epoxy Powder Pipe,Double Layer FBE Coating Pipes Application: Used for natural gas, petroleum, water & sewage, and pipe systems
Electric Fusion Welding (EFW steel pipe) refers to an electron beam welding, the use of high-speed movement of the electron beam directed impact kinetic energy is converted to heat the workpiece so that the workpiece leaving the melt, the formation of the weld. It is mainly used for welding dissimilar steel welding sheet or which high power density, metal weldment can rapidly heated to high temperatures, which can melt any refractory metals and alloys. Deep penetration welding fast, heat-affected zone is extremely small, so small performance impact on the joints, the joint almost no distortion. But it has a requirement on a special welding room because welding using X-rays.
3PE, which stands for "Three-Layer Polyethylene," is a common coating used to protect steel pipes from corrosion and extend their service life, especially in applications where the pipes are exposed to harsh environments, such as in the oil and gas industry
