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    海洋平台导管架牺牲阳极失效机理

    Failure Mechanism of Sacrificial Anodes for Offshore Platform Jacket

    • 摘要: 以胜利海域海洋平台导管架阴极保护为主要研究对象,现场勘察其海生物附着情况,通过室内试验研究了牺牲阳极的腐蚀形貌、工作电位和活化特性等,并据此分析了海生物附着条件下牺牲阳极失效的关键原因。结果表明:海生物附着在导管架的平均厚度为16.65 cm,最大厚度为31.7 cm,平均覆盖率高达95.58%,这导致现场牺牲阳极的平均实际电容量仅为1 068.57 A·h/kg,电流效率为38.8%,远低于规范中≥85%的要求,其平均消耗率为8.21 kg/(A·a),远高于规范中≤3.50 kg/(A·a)的要求。海生物覆盖抑制了牺牲阳极的活化性能,加剧了点蚀。当试验时间为30 d时,未去除产物层牺牲阳极的平均腐蚀速率仅为0.156 mm/a,最大蚀坑深度为136.829 μm,开路电位为-0.89 V,而去除产物层牺牲阳极的平均腐蚀速率为4.329 mm/a,最大蚀坑深度为27.185 μm,开路电位为-1.09 V。

       

      Abstract: The cathodic protection of offshore platform jacket in shengli sea area was taken as the main object of study. Field surveys were conducted to assess marine biofouling conditions, while laboratory experiments examined the corrosion morphology, working potential, and activation behavior of the sacrificial anodes. Based on these findings, the key factors leading to sacrificial anode failure under the condition of marine biofouling were systematically analyzed. The results show that marine biofouling on the jacket structure reached an average thickness of 16.65 cm with a maximum of 31.7 cm, exhibiting an exceptionally high average coverage rate of 95.58%. This severe biofouling directly caused significant performance degradation of the sacrificial anodes: the actual average capacitance measured only 1 068.57 A·h/kg with a current efficiency of merely 38.8%, far below the standard requirement of ≥85%. Concurrently, the consumption rate averaged 8.21 kg/(A·a), substantially exceeding the specified limit of ≤3.50 kg/(A·a). The coverage of marine organisms inhibited the activation properties of the sacrificial anodes and intensified pitting corrosion. After 30 days of testing, the anodes covered with corrosion product layers showed an average corrosion rate of only 0.156 mm/a, maximum pit depth of 136.829 μm, and open-circuit potential of -0.89 V, while the sacrificial anodes uncovered with corrosion product layers exhibited a considerably higher average corrosion rate of 4.329 mm/a, shallower maximum pit depth of 27.185 μm, and more negative open-circuit potential of -1.09 V.

       

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