Effect of cathodic protection on corrosion of pipeline steel under disbonded coating

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• 作者：X. Chen ; X.G. Li ; C.W. Du ; Y.F. Cheng
• 关键词：A. Steel ; C. Cathodic protection ; C. Crevice corrosion ; C. Oxygen reduction ; C. Polymer coating
• 刊名：Corrosion Science
• 出版年：2009
• 出版时间：September 2009
• 年：2009
• 卷：51
• 期：9
• 页码：2242-2245
• 全文大小：314 K

文摘

In this work, a test rig was developed to study the effect of cathodic protection (CP) on corrosion of X70 pipeline steel in the crevice area under disbonded coating through the measurements of local potential, solution pH and dissolved oxygen concentration. Results demonstrated that, in the early stage of corrosion of steel, CP cannot reach the crevice bottom to protect steel from corrosion due to the geometrical limitation. Corrosion of steel occurs preferentially inside crevice due to a separation of anodic and cathodic reaction with the depletion of dissolved oxygen in the crevice solution. The main role of CP in mitigation of sequential corrosion of steel in crevice under disbonded coating is to enhance the local solution alkalinity. With the increase of distance from the open holiday, a high cathodic polarization is required to achieve appropriate CP level at crevice bottom. A potential difference always exists between the open holiday area and inside crevice, reducing the CP effectiveness.