单层保温管外腐蚀失效模式及改进方法研究

发布时间：2018-07-04 07:34

本文选题：海底管道 + 管道节点　；参考：《大连理工大学》2015年硕士论文

【摘要】：随着海洋油气资源的大量开采,海底管道作为海洋资源输运最重要的途径,其腐蚀问题已引起了高度的重视。由于海底管道长期处于恶劣的海洋环境中,其外腐蚀破坏的原因也十分复杂,而近几年运行期单层保温管道腐蚀事故的频发,也暴露出国内对其外腐蚀的原因及事故的应对措施研究的不足。因此,本论文拟通过试验的方法,涉及材料科学,海洋环境学及化学与化工等学科,结合工程实际情况,对海底管道的外腐蚀成因进行分析、研究,同时给出各原因的解决方法。本论文通过对国、内外大量文献进行研究的基础上,对海底管道的故障原因进行了归纳、总结,统计得出海底管道外腐蚀故障发生的特点及规律,并进一步深入研究。论文选取其中一条发生外腐蚀破坏事故的管道进行参数和腐蚀检测结果的分析,并通过设计实验室水池试验对事故进行模拟,从而针对试验结果,对事故的原因进行猜想和假设。本文作者从假设出发,设计试验对管道材料的电化学性能进行研究,利用失重法、表面状态观察、稳态极化曲线法、电极电位测量等方法,探究温度、酸碱度、盐度等因素对管线材料抗腐蚀性能的影响,同时,对材料的抗点蚀能力、阴极屏蔽现象及氧浓差电池的加速现象进行分析研究,并给出相关影响因素的改进方法。本论文的主要结论有：(1)管线材料X65钢材的在不同温度、盐度及酸碱度的条件下,其耐点蚀性能较好,通过对极化曲线及表面状态的分析,材料不存在点蚀倾向；(2)在3.5%的NaCl溶液中,温度升高会造成自腐蚀电位的负移,腐蚀速率加快；在不同盐度的溶液中,试验用的X65钢材料的腐蚀速率会随着Cl一浓度的增大而降低：针对盐度、温度相同,但pH不同的溶液,pH=3的弱酸性溶液会加速腐蚀的腐蚀行为,使X65钢的腐蚀速率明显上升；(3)管线补口处所使用的PE材料热收缩套和防水帽表面能较低,容易发生分离引起进水事故；该材料对阴极保护电流的屏蔽效果十分明显,在其阴极保护的作用下,进水区域的电极电位接近材料自腐蚀电位,无法对进水区域的达到保护的效果。因此本文针对PE材料补口的问题,提出了通过使用无屏蔽涂层,从而规避因阴极屏蔽现象造成的管道外腐蚀；(4)管线钢材料X65钢在氧浓差腐蚀电池的作用下,贫氧区域的金属做阳极,其腐蚀速率会有明显的加速,达到正常腐蚀速率的3倍,因此,本文从材料成分的角度进行调查、研究,得出不同组分对氧浓差腐蚀电池的影响。
[Abstract]:With the exploitation of offshore oil and gas resources, the corrosion of submarine pipelines, as the most important way to transport marine resources, has attracted great attention. Because the submarine pipeline is in the bad marine environment for a long time, the reason of its external corrosion damage is also very complicated, and in recent years, the corrosion accident of the single-layer insulation pipeline occurs frequently in recent years. It also exposed the lack of domestic research on the causes of external corrosion and the measures to deal with the accident. Therefore, this paper intends to pass the experimental method, involving materials science, marine environment science, chemistry and chemical engineering and other disciplines, combined with the actual situation of engineering, the causes of external corrosion of submarine pipelines are analyzed and studied. At the same time, the solutions of various reasons are given. On the basis of studying a lot of domestic and foreign literatures, this paper sums up and summarizes the fault causes of submarine pipelines, and obtains the characteristics and rules of the external corrosion faults of submarine pipelines by statistics, and makes further research on them. In this paper, the parameters and corrosion detection results of one of the pipelines with external corrosion failure are analyzed, and the accident is simulated through the design of laboratory pool test, which aims at the test results. Guess and hypothesize the cause of the accident. Based on the hypothesis, the author designs experiments to study the electrochemical properties of pipeline materials. By means of weightlessness method, surface state observation, steady-state polarization curve method, electrode potential measurement and so on, temperature, pH and alkalinity are investigated. The effects of salinity and other factors on the corrosion resistance of pipeline materials are also analyzed and studied, including the pitting resistance, cathodic shielding and the acceleration of oxygen concentration cells, and the improvement methods of related factors are given. The main conclusions of this paper are as follows: (1) the pitting corrosion resistance of pipeline material X65 steel is better under different temperature, salinity and pH. Through the analysis of polarization curve and surface state, there is no pitting corrosion tendency. (2) in 3.5% NaCl solution, the increase of temperature will result in negative shift of corrosion potential and increase of corrosion rate, and in different salinity solution, the corrosion rate of X65 steel will decrease with the increase of Cl ~ (-) concentration: for salinity, the corrosion rate of X65 steel will decrease with the increase of Cl ~ (-) concentration. The corrosion behavior of X65 steel was accelerated by weak acid solution with different pH and different pH, and the corrosion rate of X65 steel was obviously increased. (3) the surface energy of heat shrink sleeve and waterproof cap of PE material used in pipeline repair was lower. The shielding effect of the material on cathodic protection current is very obvious. Under the action of cathodic protection, the electrode potential in the influent area is close to the self-corrosion potential of the material. Unable to reach the protection effect on the influent area. In order to avoid the pipeline corrosion caused by cathodic shielding phenomenon, this paper proposes to avoid the pipeline corrosion caused by cathodic shielding by using unshielded coating. (4) the pipeline steel X65 steel is under the action of oxygen concentration corrosion cell. The corrosion rate of the metal anode in the oxygen-poor region will be obviously accelerated to 3 times of the normal corrosion rate. Therefore, this paper investigates and studies the effect of different components on the oxygen concentration corrosion cell from the point of view of material composition.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P756.2;P755.3

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