Corrosion Monitoring of Steel Structures in Marine Environments and Microbial-Induce Corrosion in Seashore of China

本研究项目的主要目标是建立一种评价海洋环境中建造的钢结构的腐蚀性能和电阻率的方法，测量中国海岸的环境腐蚀性，并确定微生物引起的腐蚀随温度、土壤和污染的差异。对中国4个不同海岸带的腐蚀速率进行了连续10个月的监测。对超细晶粒钢(Al-Si钢和Al-Si-Ni钢)、顺序耐候钢、海洋耐候钢(3%Ni钢)、碳钢和不锈钢(SUS304)6种钢的腐蚀速率进行了监测，结果表明，除不锈钢外，其余钢的腐蚀速率受平均温度和析出量的影响较大。而不锈钢则依赖于离海岸线的距离。这表明，样品上积累的空气骨盐的数量决定了不锈钢的腐蚀或锈蚀。本项目未澄清微生物诱导的腐蚀与污染之间的关系。中国科学院海洋研究所侯宝荣教授是该项目的合作者，他在这一主题上的积极工作将在不久的将来澄清。Tanji教授的团队在本项目中发现，阴极保护电流抑制了生物膜的初始形成和生长，从而抑制了微生物诱导的腐蚀。

Main objectives of this research project are that to establish a method to evaluate the corrosion property and resistivity of steel structures built in a marine environment, to measure the environmental corrosivity of sea coasts of China, and to confirm differences in microbial-induced corrosion depending upon temperature, soils or pollutions.In this research project, the corrosion monitor developed by the authors based on ac impedance method was successfully applied to continuous measurement of corrosion rate of several kinds of steels. The corrosion rates at four different sea coast in China were monitored continuously for ten months. Corrosion rate of six kinds of steels, very fine grain steels (Al-Si steel and Al-Si-Ni steel), ordinal weathering steel, marine weathering steel (3%Ni steel), carbon steel and stainless steel (SUS304), were monitored and it was revealed that corrosion rate of steels, except for stainless steel, were largely influenced by the average temperature and amount of precipitation. On the other hand, that of stainless steel depended upon the distance from sea coast. It suggested that the amount of air bone salts accumulated on the specimens determine the corrosion or rusting of stainless steel.The relation between the microbial-induced corrosion and pollution was not clarified in this project. Vigorous works on this subject by Prof. Baorong Hou (Institute Oceanology, Chinese Academy of Science) who was a collaborator of this project will clarify this in near future. It was found by Prof. Tanji's group in this project that current of cathodic protection suppresses initial formation and growth of bio-film and this will lead to inhibit microbial-induced corrosion.