Looking back at the anti-corrosion history of oil and gas pipelines, the application of powder coatings has raised their corrosion protection to a new level.

20th Century 50&Dash; In the 1960s, the external anti-corrosion coating of pipelines in China was mainly composed of asphalt coatings; After 70‐ In the 1980s, coal tar enamel coating (CTE) made its debut on the historical stage; From epoxy coal tar in the late 1980s to fusion bonded epoxy powder coating (FBE) in the 1990s, the coating construction method of anti-corrosion coating has gone through more than 40 years, from liquid-phase fluid coating to solid-phase powder coating.

The polyethylene tape and polyethylene hot coating technology that emerged in the 1990s have made significant breakthroughs in the speed and quality of pipeline anti-corrosion processes; In the late 1990s, double-layer epoxy coating (DPS) and polyethylene three-layer composite structure (3LPE) were widely used for anti-corrosion protection of oil and gas pipelines due to their good anti-corrosion performance, mechanical properties, and scratch resistance.

Hot coated polyethylene powder

The Polyethylene Powder Thermal Coating (FBP) anti-corrosion coating technology for steel pipelines, commonly known as single-layer PE technology, is the process of coating modified high-density, low-density, or linear low-density polyethylene powder onto the surface of a medium frequency heated steel pipeline through a spray coating method, causing it to melt and utilize the natural flow properties of the molten liquid to uniformly adhere to the metal surface. After condensation, a tight anti-corrosion coating is formed.

After 2000, the China Petroleum Pipeline Science Research Institute transformed it into a continuous operation line coating, improving production efficiency and reducing production costs, and successfully applied it on the Ø 355 mm Xiangtan Liling branch line. However, this method imposes certain limitations on the speed and efficiency of anti-corrosion construction for large-diameter pipelines over 600 mm.

Thermosetting material coatings

The main varieties of thermosetting coatings include epoxy resin, amino alcohol acid, acrylic acid, and polyurethane.

FBE coating technology

Epoxy powder coating is a thermosetting powder coating with corrosion resistance and toughness. In the late 1980s, the introduction of epoxy powder technology from abroad to China was promoted by the China Petroleum Pipeline Research Institute in the early 1990s. The commonly referred FBE is a single-layer epoxy powder with a simple coating process.

Due to the strong adhesion of epoxy powder coating to metals, good mechanical properties of the coating, certain hardness and scratch resistance, and excellent corrosion resistance within the standard moisture content range, it is widely used in long-distance oil and gas pipelines and gathering pipelines. However, FBE also has its own weaknesses, as a thin anti-corrosion layer is not suitable for use in mountainous and Gobi gravel environments; In addition, the degradation of epoxy resin under ultraviolet light irradiation is also a shortcoming that makes FBE anti-corrosion pipelines unsuitable for long-term outdoor storage. Double layer epoxy powder coating technology

Around 2000, a double-layer epoxy powder coating structure emerged. Double layer epoxy powder is made by using ordinary single-layer fusion bonded epoxy powder as the base coating and modified fusion bonded epoxy powder as the outer protective layer. This double-layer fusion bonded epoxy powder anti-corrosion system structure greatly improves the mechanical properties of the anti-corrosion layer, enhances its impact resistance, high temperature resistance, and permeability resistance at high temperatures. At the same time, it maintains the compatibility between the single-layer fusion bonded epoxy powder anti-corrosion layer and cathodic protection, without producing cathodic protection shielding. The thickness of its overall anti-corrosion layer is between 550~1000 mm, and the maximum operating temperature is 115 ℃.

DPS anti-corrosion technology is generally used for elbows and special-shaped parts of various pipe diameters. Qutu Coatings (Qutu Network) has learned that this anti-corrosion method is used for hot bending pipes from the Senninglan pipeline, Lanzhou Chengdu Chongqing pipeline to the West East Gas Pipeline and Central Asia International Pipeline.

Two component thermal spraying technology

The thermal spraying technology of two-component coatings was developed in the 1980s and 1980s; In the 1990s, anti-corrosion technology was very popular and mainly used for pipeline overhaul. Two types of materials were heated separately to enhance their fluidity and reactivity. They were mixed in a certain proportion before spraying at the nozzle, and then the mixture was coated on the surface of the steel pipe through a spray gun. Two component materials undergo rapid curing reactions under the influence of temperature, forming a coating layer. Epoxy resin, amino alcohol acid, acrylic acid, and polyurethane materials are all suitable for two-component coating. The domestic two-component thermal spraying technology is widely used in the repair of the Northeast pipeline network.

Double layer anti-corrosion structure

Double layer anti-corrosion structural steel pipe, namely 2PE polyethylene anti-corrosion steel pipe, with the first layer of adhesive (AD); Second layer of polyethylene (PE). Two materials are integrated into one, and the thickness of the adhesive layer is not less than 70 μ m; m， The polyethylene layer should not be less than 2.5 mm, and the double-layer polyethylene anti-corrosion structure mainly relies on the polyethylene layer. The winding construction can be carried out mechanically or manually, and the hollowing and cathodic shielding caused by the anti-corrosion layer are inevitable.

Due to its lack of epoxy layer, its adhesion, cathodic peel resistance, and anti-corrosion performance are inferior to those of three-layer composite structures. However, its production process is relatively simple and inexpensive, and it is generally used in urban water pipelines. In the field of oil and gas pipelines, it is basically replaced by 3PE.

Three layer composite structure

The three-layer composite structure is a corrosion-resistant structure that combines the excellent adhesion and high resistance to cathodic delamination of FBE with the high impermeability, high protection, good mechanical properties, and soil stress resistance of polyolefin materials. If polyethylene is used as the outermost layer of the three-layer composite structure, it is referred to as 3LPE; If polypropylene is used as the outermost layer, it is referred to as 3LPP.

This anti-corrosion form was first widely applied on the Shaanxi Beijing natural gas pipeline in China in the late 1990s, and the effect was good. Up to now, the anti-corrosion process has become very mature, the technical standards are perfect and reliable, polyethylene is used, and the production cost has been reduced to about 10 US dollars per square meter. It is basically the standard configuration for external corrosion protection in domestic pipeline construction. Since 2000, multinational oil and gas pipelines constructed by PetroChina, such as the China Kazakhstan crude oil pipeline, the Central Asia natural gas pipeline, the China Myanmar oil and gas pipeline, and the China Russia oil and gas pipeline, have all adopted 3LPE anti-corrosion coating technology without exception.

Summary:

In addition to oil and gas pipelines, powder coatings can be used for coating in fields such as home appliances, furniture, automobiles, building materials, and outdoor facilities. Powder coatings can meet different requirements for appearance, weather resistance, corrosion resistance, and other properties, with high performance, wide applications, and a large market space. It is expected that by 2024, the market size of the domestic powder coating industry will reach around 50 billion yuan.