Anticorrosive coating technology for oil and gas pipeline

Corrosion is the basic factor affecting the life and reliability of subsea and buried oil and gas pipelines Therefore, in the design and construction of pipelines, anti-corrosion coating is usually applied on the pipelines, and effective cathodic protection system is added to effectively resist the pipeline corrosion In the past 50 years, oil and gas pipelines have been coated with many different kinds of coatings, such as coal tar enamel, petroleum asphalt, polyolefin tape wrapping, two-layer extruded polyethylene coating, single or double layer fusion bonded epoxy powder coating, reinforced three-layer or multi-layer polyolefin (polyethylene or polypropylene) coating, etc With the development of petroleum industry, oil and gas pipelines need to be applied in some special environments, and pipeline coating system also needs technical innovation Bredero Shaw has the largest technical and service expert team in the industry, with 27 pipeline coating production lines on six continents Several unique and advanced protection technologies designed by the company, including high-efficiency composite coating system (HPCC), low-temperature coating technology of high-strength steel powder coating and thermotite steady flow assurance technology, have been proved to be reliable by field application 1 High efficiency composite coating system (HPCC) high efficiency composite coating system (HPCC) is a multi-component coating system with full powder coating: the inner layer is FBE (fusion bonded epoxy resin), the outer layer is medium density polyethylene coating, and the middle layer is chemical modified polyethylene adhesive, which plays a bonding role All materials of the three components of the composite coating are coated by electrostatic powder spraying system The adhesive layer in the middle is a mixture of adhesive and FBE of certain concentration, so that there is no burr between the adhesive and the FBE of the bottom layer, or between the adhesive and the polyethylene coating of the outer layer, and there is a clearly defined interface Adhesive and polyethylene are actually similar substances that can be easily mixed together, so the coating can be closely linked to each other, like a single coating system, without delamination Even if there is a huge temperature difference, the internal stress growth of HPCC is very small HPCC has excellent adhesion to pipeline surface, excellent inherent shear resistance, low temperature flexibility, impact resistance, cathodic disbonding resistance and very low permeability 2 At present, high yield strength steel is more and more used in the construction of oil and gas pipeline In cold climate, the coating on high-strength steel must be able to withstand the test of low temperature and maintain the required flexibility of the pipeline As a general practice, the steel pipe must be preheated to 240 ℃ before FBE coating However, such a high preheating temperature will change the metallurgical properties of high-strength steel and make the metal more brittle, so that the adaptability of steel to cold climate will be reduced In order to maintain the mechanical properties of high-strength steel, the coating temperature of steel pipe must be lower than 200 ℃ when FBE coating is applied Bredero Shaw company has developed a special HPCC coating process, which can reduce the coating temperature to below 180 ℃, and has achieved satisfactory results in the pipeline projects in Canada and the United States In the process of unloading and loading casing at the construction site, the coating has no damage; in the low temperature bending of - 45 ℃, there is no damage to the anticorrosive coating 3 Thermotite current stabilizing assurance technology thermotite insulation and current stabilizing assurance technology is used to meet the requirements of corrosion protection, insulation and unobstructed assurance Thermotite technology is composed of multi-layer polyethylene, and the bottom layer is connected with the steel matrix by fusion bonded epoxy powder The structure of the five tier system is to coat the three inner layers by side extrusion or extrusion Before coating the two thermal insulation layer (polypropylene foam layer and outer jacket layer), the quality of the three layers should be tested In the thermal insulation production line, the polypropylene foam layer and outer jacket layer should be simultaneously coated by extrusion, so as to ensure that the foam does not contain air Compared with the traditional polypropylene foam structure, it is a special polypropylene foam used in Thermotite system, and its foam cell structure is more reasonable This foam has many excellent properties, such as high melting strength, high creep resistance and high hardness, which can be applied to underwater 1500m If deeper water is needed, the insulation solution of up to seven layers can be applied At the same time, glass particles are added to the matrix solid polyethylene to reinforce the composite foam to enhance the water resistance and low temperature performance of the multi-layer polypropylene system.