【作者】 丁清苗；

【导师】 李自力；

【作者基本信息】 中国石油大学 ， 油气储运工程， 2010， 硕士

【摘要】 传统经验认为交流电流所产生的干扰不能造成管道的腐蚀,其主要危害在于故障电流对人身安全造成威胁,但是近年来人们已经觉察到交流电气化铁轨等交流源对埋地金属管道的交流腐蚀危险和对阴极保护系统的交流干扰影响都增大了。由交流电流所产生的腐蚀干扰是一个相对新的现象,而且腐蚀行为比在通常的介质中要复杂得多,因此研究方法具有某些特殊性和一定的困难。为了快速而准确地测定金属材料在土壤介质中的腐蚀随时间的变化规律,本文选择符合青岛土壤情况的模拟试验溶液,进行交流干扰对管道腐蚀影响的实验室模拟试验和研究。通过测量管线钢X70钢的自腐蚀电位随时间的变化曲线及极化曲线和交流阻抗谱研究了X70钢在施加交流干扰时其相关电化学参数的变化规律,以及腐蚀速率的变化规律,从而初步探讨研究了交流干扰下土壤腐蚀机理。结果表明试样在有交流干扰时比没有干扰自腐蚀电位更负,且随着交流干扰电压的增大为负移趋势;自腐蚀电流变大,也随着交流干扰电压的增大而呈现增大趋势;腐蚀过程由阴极反应控制变成混合控制,腐蚀速度加剧。虽然阴极保护在一定程度上可以抑制交流腐蚀,但是在交流干扰防护标准中,继续使用中性溶液中碳钢的保护电位-770mVSCE就不一定合理了,因此在有交流电压干扰的阴极保护中,选择最适当的保护电位,对于抑制腐蚀,节约能源以及防止过保护造成的危害是十分重要的。本文提出在阴极保护工程中使用最佳保护电位来代替保护电位。采用电化学方法测量X70钢在不同交流干扰电压下的极化曲线、恒电位极化曲线和不同阴极极化电位下的电化学交流阻抗谱,建立了确定交流干扰腐蚀下阴极保护电位范围和最小及最佳保护电位的方法。结果表明,采用电化学测试方法可以确定X70钢的在有交流干扰的条件下的阴极保护参数,并建议在本实验条件下X70钢的最小保护电位为交流干扰电压较小时(≤4V)在-815mVSCE左右,交流保护电压较大时(≥5V)-835mVSCE左右;最佳保护电位在交流干扰电压较小(≤6V)时-900mVSCE左右,交流干扰电压较大(≥7V)时-1000mVSCE左右。更多还原

【Abstract】 Traditional experiences showed that the current generated by AC could not cause corrosion of pipelines,and the main hazard was that the fault current threated to human security. But in recent years, people have awared that AC(such as the high-voltage transmission lines) would cause corrosive threat to the buried pipeline. The corrosion risk caused by AC is a relatively new phenomenon, and its corrosion behavior is much more complex than that in the usual medium, so research method has certain peculiarities and some difficulties.In order to quickly and accurately determine the corrosion rate over time of the metal material in the soil medium, this paper choosed test solution to simulate Qingdao soil for laboratory research of the pipeline corrosion interfered by AC. By measuring the X70 steel corrosion potential changing with time、polarization curves and AC impedance I studied the variation of electrochemical parameters on the X70 steel interfered by AC, as well as the changes of corrosion rate and thus studied initialy mechanism of soil erosion under the interference of AC. The results showed that when X70 steel was interfered by certain AC its corrosive potention was decrescent,its corrosive current was accrescent, and the process of corosion was changed from cathoding control to blending control,then corrosion rate increased.The cathodic protection could inhibit the exchange of corrosion to a certain extent. But in the AC interference protection standards, the continued use of carbon steel protection of potential(-770mVSCE) in neutral solution is not necessarily appropriate, so it is very important to select the most appropriate protection potential for inhibiting corrosion, energy conservation and preventing the harm caused by excessive protection under the AC voltage interfere. This paper proposed the use of the best potential in stead of the protection potential. Used electrochemical methods to research the corrosion characteristics of the X70 steel under different alternating stray current (AC)voltage and got polarization curves、potentiostatic polarization experiments and electrochemical impedance spectroscopy(EIS) under different cathodic polarization potential to determine the scope of its cathodic protection potential and the optimum cathodic protection potentia. The results showed that the use of polarization curves、potentiostatic polarization experiments and electrochemical impedance spectroscopy could determine the conditions of cathodic protection parameters of the X70 steel under different AC voltage.At last I suggested that in my experiment conditions the smallest cathodic protection potential of the X70 steel under different AC at a smaller voltage was -815mVSCE ,while at a larger selected -835mVSCE around and the optimum cathodic protection potential under different AC at a smaller voltage was -900mVSCE ,while at a larger selected -1000mVSCE around.更多还原