Understanding the process of PE coated steel pipe

PE-coated steel pipes, commonly used in various industries such as oil and gas, water transportation, and construction, provide superior protection against corrosion. The coating process involves several layers of materials that work together to protect the pipe and ensure its durability. Let’s explore the two primary types of PE coating systems—3PE and 2PE—and their manufacturing processes.

3PE Anti-Corrosion Coating

The 3PE (three-layer polyethylene) anti-corrosion coating is one of the most advanced methods used for protecting steel pipes. It consists of three distinct layers, each serving a specific purpose to enhance the overall performance:

- Epoxy Coating (Bottom Layer)
The first layer is an epoxy powder coating, which is applied to the steel pipe surface at a thickness greater than 100 microns (FBE > 100 μm). This layer provides excellent anti-corrosion properties and serves as a protective barrier against rust and other environmental factors.

- Polymer Adhesive (Middle Layer)
The middle layer is a polymer adhesive, typically a modified polyolefin, which contains polar groups grafted onto the main chain of the polyolefin. This modification allows the adhesive to fuse effectively with both the epoxy layer and the polyolefin layer, enhancing the bonding strength between the layers. The adhesive ensures a strong and durable bond, which is crucial for the integrity of the anti-corrosion system.

- Polyethylene (Surface Layer)
The outermost layer is made of polyethylene (PE), with a thickness ranging from 2.5 to 3.7 mm. This layer provides mechanical protection to the pipe, preventing physical damage and offering excellent resistance to external forces, such as abrasion and impact. Polyethylene also offers additional protection against the effects of environmental factors, such as moisture and chemicals.

The three materials work together to create a strong, multi-functional anti-corrosion system. The epoxy powder provides excellent corrosion resistance, while the polyethylene offers scratch protection. The adhesive layer ensures optimal bonding between the epoxy and polyethylene, addressing issues related to the adhesion of polyethylene and ensuring the effectiveness of cathodic protection systems.

- Key Characteristics of 3PE Coating:

The adhesive layer allows for a strong bond between the three materials.

High cost due to the complexity of the process.

High requirements for the surface treatment of the steel pipe, with an anchor pattern depth of 50–75 μm.

Provides excellent anti-corrosion, mechanical protection, and waterproof properties.

2PE Anti-Corrosion Coating

The 2PE (two-layer polyethylene) anti-corrosion coating is a simpler version of the 3PE system, typically used in applications where high-performance protection is required but with a more cost-effective solution. This coating system consists of two layers:

- Adhesive Layer (AD)
A single layer of adhesive is applied to the surface of the steel pipe to bond the polyethylene to the pipe. The adhesive layer serves as the bonding agent between the steel and the polyethylene, ensuring the coating remains securely attached.

- Polyethylene (PE) Layer
The polyethylene layer in the 2PE system is applied in two separate layers, with each layer having a thickness similar to the individual layers in the 3PE system. The polyethylene layer provides mechanical protection and resistance to corrosion and other external factors.

- Key Characteristics of 2PE Coating:

A simpler, more cost-effective alternative to 3PE.

Suitable for environments with less severe corrosion or mechanical stress.

Provides good protection against corrosion and external damage.

In summary, the 3PE and 2PE anti-corrosion coatings offer different levels of protection, with 3PE providing superior performance for more demanding applications. Both systems play an important role in extending the life of steel pipes and ensuring their reliability in various industries.