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首页> 外文期刊>Iranian journal of chemistry & chemical engineering >An Electrochemical Measurement for Evaluating the Cathodic Disbondment of Buried Pipeline Coatings under Cathodic Protection
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An Electrochemical Measurement for Evaluating the Cathodic Disbondment of Buried Pipeline Coatings under Cathodic Protection

机译：评估阴极保护下埋藏管道涂料阴极剥离的电化学测量

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摘要

Steel pipelines are susceptible to corrosion by the action of corrosive substance in the environment and one of the most common failure modes in buried pipeline coating is cathodic disbondment. Consequently, Electrochemical Impedance Spectroscopy (EIS) was used to assess the effect of three important parameters, the thickness of coating, the artificial defect and electrolyte type, on cathodic disbondment, according to ASTM G8. Experiments were done in 3.5 % wt NaCl, KCl and CaCl2 solutions at room temperature with different coating thicknesses (354, 483 and 1014 mu m) and several artificial defects diameters (3, 6 and 9 mm). Immersion time was 28 days and during this period, a - 1.5 V cathodic potential (vs. SCE) was applied. Further, the EIS measurements were done in Open Circuit Potential (OCP). Investigations showed that a thick polyurethane coating was highly resistant to cathodic disbondment in intact areas and that coating thickness increases caused decreases in the rate of cathodic disbondment in areas with defects. On the other hand, the evaluation on artificial defects showed disputable results, though with no logical correlations between artificial defects' diameters and any disbonded area individually. In addition, assessment on electrolyte type showed the rate of cathodic disbonding might be classified after two parameters: solubility and mobility of ions. So, the disbonded area was dependent on the cation type in the electrolyte, and the anion diffusion had less effect in the cathodic disbondment process. Furthermore, the comparison between the cations and the anions in solution showed that the most important coating disbondments occurred when cations / anions are in a 1:1 ratio.
机译：钢质管道易受环境中腐蚀性物质的作用腐蚀，并且埋入式管道涂料中最常见的失效模式之一是阴极脱胶。因此，根据ASTM G8，使用电化学阻抗谱（EIS）评估了三个重要参数（涂层厚度，人工缺陷和电解质类型）对阴极剥离的影响。在室温下在3.5％wt的NaCl，KCl和CaCl2溶液中进行实验，具有不同的涂层厚度（354、483和1014μm）和几种人工缺陷直径（3、6和9 mm）。浸入时间为28天，在此期间，施加了-1.5 V阴极电位（相对于SCE）。此外，EIS测量以开路电位（OCP）进行。研究表明，厚的聚氨酯涂层对完整区域的阴极剥离具有很高的抵抗力，而涂层厚度的增加会导致缺陷区域的阴极剥离速率降低。另一方面，对人造缺陷的评估显示出有争议的结果，尽管在人造缺陷的直径和任何剥离面积之间没有逻辑关联。另外，对电解质类型的评估表明，阴极解离的速率可以根据两个参数进行分类：离子的溶解度和离子迁移率。因此，剥离面积取决于电解质中的阳离子类型，而阴离子扩散在阴极剥离过程中的影响较小。此外，溶液中阳离子和阴离子之间的比较表明，当阳离子/阴离子的比例为1：1时，最重要的涂层剥离发生。

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