流动海水环境下沉管隧道钢壳外壁冲刷腐蚀规律研究

Erosion Corrosion Rule of Steel Shell Outer Wall of Immersed Tube Tunnel in Flowing Seawater Environment

沉管隧道钢壳外壁处于复杂腐蚀环境中,形成了复杂体系的电化学腐蚀发生发展规律,其中流动海水冲刷引起的加速腐蚀效应十分明显。首先以深中通道沉管隧道外壳Q390C钢板为对象,分别考虑静止和流动海水2类腐蚀环境的影响,开展了无涂层无阴极保护、有涂层无阴极保护及有涂层有阴极保护下钢板腐蚀性能试验研究,对试验值进行了分析。其次,基于钢板腐蚀速率计算公式,结合试验数据,将静止海水环境下钢板腐蚀试验值作为基本因子,对涂层防护、阴极保护及流动海水效应等因素进行了理论计算,给出了相应钢板腐蚀率计算公式,并对其腐蚀机理进行了讨论。最后,将文献试验数据及ASTM规范公式结果进行了对比。结果表明:对于不同防护条件,当腐蚀发生5个月时,在静止海水和流动海水环境下,无涂层无阴极保护工况下钢板腐蚀速度均为最快;有涂层无阴极保护工况对钢板的防腐效果均优于无涂层无阴极保护工况;对于有涂层有阴极保护工况,静止海水环境中钢板的防腐效果要优于无涂层无阴极保护,但稍差于有涂层无阴极保护,而流动海水环境中钢板的防腐效果均优于无涂层无阴极保护和有涂层无阴极保护工况;对于3种防腐工况,流动海水环境中钢板腐蚀程度均高于静止海水环境,且前者为后者的2倍左右;所建公式能较好地反映不同因素组合下钢板腐蚀规律,可为准确评估实际环境影响因素下沉管隧道钢壳外壁腐蚀行为及防护效果提供依据。

The steel shell outer wall of immersed tunnel is in a complex corrosion environment, forming an electrochemical corrosion occurrence and development rule of complex system, in which the accelerated corrosion effect caused by flowing seawater scouring is very obvious. First, taking the Q390 C steel plate for immersed tube tunnel shell of Shenzhen-Zhongshan Passage as the object, considering the influence of static and flowing seawater corrosion environment respectively, the corrosion performance of the steel plate is experimental studied under the condition of no cathodic protection without coating, no cathodic protection with coating and cathodic protection with coating. The test data are analysed. Second, based on the calculation formula of steel plate corrosion rate, combining with the test data, taking the steel plate corrosion test value in static seawater environment as the basic factor, the factors such as coating protection, cathodic protection and flowing seawater effect are theoretically calculated, the corresponding calculation formula of steel plate corrosion rate is given, and its corrosion mechanism is discussed. Finally, the test data in literature and the result obtained by ASTM specification formula are compared. The result shows that(1) for different protection conditions, when the corrosion occurs for 5 months, in static seawater and flowing seawater environment, the corrosion rate of steel plate without coating and no cathodic protection is the fastest;(2) the anti-corrosion effect of coated steel plate without cathodic protection is better than that of uncoated steel plate without cathodic protection;(3) for the working condition with coating and cathodic protection, the anti-corrosion effect of steel plate in static seawater environment is better than that without coating and no cathodic protection, but it slightly worse than that of coated steel plate without cathodic protection, while the anti-corrosion effect of steel plate in flowing seawater environment is better than that without coating and no cathodic protection and that with coating and no cathodic protection;(4) for the 3 anti-corrosion conditions, the corrosion degree of steel plate in flowing seawater environment is higher than that in static seawater environment, and the former is about twice that of the latter;(5) the established formula can better reflect the corrosion rule of the steel plate under different factor combinations, which can provide a basis for accurately evaluating the corrosion behavior and protection effect of steel shell of immersed tube tunnel under actual environmental influencing factors.