Cailiao Baohu (May 2022)
Study on the Influence Law of Asphalt Anti - Corrosion Coating Protection Efficiency Based on Performance Degradation
Abstract
In China, the sacrificial anode cathodic protection systems of many pipelines in service with asphalt coating have failed or are about to fail. If the sacrificial anode systems are replaced according to the original design, some pipelines could not be effectively protected. In this work, based on the surface resistivity change rule of the anticorrosive layer of on - site pipeline with time, the change of resistivity of the as - mentioned anticorrosive layer in the next 20 years was predicted. The change of protection distance of pipeline after 15 years of operation with time was estimated using simulation calculation, which provided a basis for the redesign of cathodic protection system. Results showed that the surface resistivity of anticorrosive layer of asphalt coating decreased with the prolonging of burried time, and the decreasing rate decreased gradually; the damage rate of anticorrosion coating increased with the prolonging of buried time, and the increase rate rised gradually. After 15 years of operation single group sacrificial anode protection system, the single - side protection distance of the pipeline was 50 m. And then with the continuous service of the pipeline, the single - side protection distance decreased significantly. After 20, 25, 30 and 35 years of operation, the single - side protection distance declined to 28.0, 19.0, 14.0 and 11.5 m, respectively. When the distance between the anode and the pipeline was in the range of 1～4 m, with the increase of such distance, the potential distribution on the pipeline became more and more uniform, and the protection distance increased. Furthermore, in the next 20～35 years, the replacement time of sacrificial anode system would have little impact on the anode life, which was estimated to be about 23 years.
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