Brief Introduction of Coating Process of Conveying Pipe Anticorrosive Coating
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Last Update: 2020-02-21
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Source: Internet
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Author: User
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China's natural gas West-East gas pipeline, a total length of 4169 km, 20 billion cubic meters of gas per day, its outer wall corrosion is the use of coating and cathode protection combinedThere are several varieties of this type of pipe coating(1) oil asphalt, has been used in China for more than 30 yearsIts process for hot coated petroleum asphalt, with glass wrap, and then plastic film cover, low cost, often in the oil sector application, simple construction, its disadvantage is high water absorption rate, poor heat resistance, the use of a range of 0 to 40 degrees C, resistant to soil microorganisms, easy to be penetrated by plants, in Europe and the United States has been phased out(2) coal-coking asphalt "porcelain paint" its process for the first coating of a thin coal-coking asphalt primer, to wet the surface, and then hot watering to coat the solvent-free coal coke asphalt "ceramic paint", and then wrapped around the belt, its advantage is low water absorption, can be applied to -30 to 95 degrees C temperature range, corrosion resistance, soil bacteria, plant root penetration, low costThe disadvantage is that the smoke during construction is harmful to the health of the workers and is less compatible with cathode protectionChina in the early 1920s in Wuhan pipe pipe using this coating, after the 1950s excavation review, steel pipe is still metal gloss and corrosion-free(3) fuseep epoxy (fusebondepoxy) powder coating this process has been used in foreign countries for 30 years, with strong adhesion of steel pipe, corrosion resistance, can be used in the range of -60 to 110 degrees CThe disadvantage is poor water resistance, easy to destroy by impact, more expensiveIts operation is to blast rust to Sa2.5 level, with induction ring heating to 230 to 260 degrees C electrostatic spray epoxy powder (Novolac epoxy resin plus phenolic curing agent), the tube in the work line rotation binding binding 2 to 3min, so that the powder leveling and curing, and then spray water rapid cooling, paint film thickness of 400um(4) epoxy asphalt coating has been used abroad for 40 years, the United States began in 1959, Japan began in 1967, has been used in China for 20 yearsIts advantages are strong adhesion, water resistance, microorganism resistance, plant root penetration is good, can be used in the environment -60 to 110 degrees C environment, can be cured at room temperatureThe disadvantage is that the two components are not convenient, the coating is more brittle, the SOLVENT VOC on environmental pollution, can be used for smaller scale, pipeline diameter smaller branch projects(5) three-layer protected area of epoxy/polyethylene This is a technology developed only more than a decade ago, the operation is to apply a molten epoxy powder coating (FBE) and then combine with extruded polyethylene: epoxy powder coating, copolymer, polyethylenethis system is both resistant to corrosion and has excellent mechanical propertiesThe disadvantage is the high costChina's Shaanxi to Beijing large-calibre gas pipeline wall is the use of this technology, there are Kuller to Yanshan County, Jingbian to Xi'an and other projects areKailin paint factory Lu Boxuan introduced the plant supply of underground pipe coating process is: sand blasting up to Sa2.5 level, in the relative humidity of 85% or less, the ambient temperature is not less than 5 degrees C, the substrate temperature is higher than the dew point above 3 degrees C can be constructed;the first epoxy-rich zinc primer 80umthe second epoxy mica iron oxide anti-rust paint 100um
the third epoxy asphalt paint 200um
after each dry should measure the thickness of the coatingThe total thickness must be measured after the completion of the entire coating systemMore than 90% of the measuring points must reach the specified valueThe film thickness value that does not reach the specified value shall not be less than 90% of the specified value, otherwise the value should be recoated or addedThis system has been widely used in Shanghai, Hunan, Guangdong Shantou underground water and gas pipeline projects for 15 years, and is still in normal useAt present, China has 5 pipelines to operate, all using domestic coal tar magnetic paint, anti-corrosion pipeline quality in full compliance with SY/T0079-93 standard requirementsCoal tar magnetic paint is made of coal tar asphalt, coal powder, tantalum oil and mineral filling material, the formula is:coal tar asphalt 20% to 35% tantalum oil 25% to 35% coal powder 20% to 30% mineral filling 25% to 40% boiled should pay attention to dehydration, the whole process needs 10 to 12hLu Weizhong introduced the application of anti-corrosion technology in the water supply pipeline system, and also mentioned that the anti-corrosion coating used in the outer wall of the pipeline is oil asphalt, coal-coking asphalt porcelain paint, adhesive tape, extrusion polyethylene, epoxy asphalt and melted epoxyExtruded polyethylene is prone to stress cracking on large diameter pipes over 508mm (20 inches) by covering itthe inner wall of the water supply pipe is more corroded than the outer wallIn the late 1980s, China caused the fusion and binding powder coating from abroad Since the 1990s, the Institute of Corrosion of the Chinese Academy of Sciences has developed a molten combined epoxy powder (SEBF) and solvent-free high-performance composite liquid epoxy coating (SLF) with excellent corrosion resistance
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