海底管道大规模点腐蚀群的多尺度时空演化机理研究

Pitting corrosion is the main cause of failures for structures such as submarine pipelines. The multiscale stochastic evolution of corrosion pits is an important issue in the study of corrosion theory and corrosion prediction. Previous study mainly focused on the growth mechanism of single pit and the macroscale behavior of the corrosion process, while little attention has been payed to the stochastic evolution of the group of corrosion pits and the evolution of large-scale corrosion pits has not been studied by experimental method. In this project, a multiscale analysis method for pitting corrosion is proposed by combining the in-situ measurement and recognition of stitched images, to investigate the multiscale spatial distribution and its continuous evolution mechanism for large-scale (ten thousand to one hundred thousand points) corrosion pits and to reveal the effect of complicated environmental factors on the distribution and evolution behavior of corrosion pits. The dynamic growth model for single pit will be built to reveal the interaction mechanism of multiple corrosion pits; the large-scale spatial point pattern will be obtained by recognition of stitched images to clarify the multiscale spatial distribution behavior of large-scale corrosion pits; the continuous evolution behavior of spatial point pattern of pitting corrosion will be deeply investigated to build the multiscale spatiotemporal evolution theory of large-scale corrosion pits. In this project, the multiscale spatial modelling of large-scale defect group will be realized, through multidisciplinary approach that can overcome the difficulties of inter-scale characterization of pitting corrosion, which can provide a new way in the study of multiscale theory in related disciplines including mechanical engineering and material science. The results can provide guidance for the safe operation and corrosion-oriented design of submarine pipelines.

点腐蚀是导致海底管道等装置失效的主要原因，腐蚀点的多尺度随机演变是腐蚀机理和预测研究中的重要问题。已有研究集中在单个腐蚀点形成机制或点腐蚀的宏观表现，缺乏有关点蚀群随机演化的深入研究，大规模点蚀群演化的实验研究未见报道。本项目提出将原位测量和拼接图像识别相结合的点腐蚀多尺度分析方法，研究大规模（1万至10万点）点腐蚀群的空间多尺度分布及连续演变机理，揭示复杂环境因素对点腐蚀群分布和演化规律的影响。建立单个腐蚀点生长动力学模型，揭示多腐蚀点交互作用机制；通过拼接图像识别构建大规模空间点阵，探明大规模点腐蚀群的空间多尺度分布规律；深入研究腐蚀空间点阵的连续演化规律，建立大规模点腐蚀群的多尺度时空演化理论。本项目通过多学科交叉方法，突破点腐蚀跨尺度表征难题，实现大规模缺陷群的空间多尺度建模，可为机械、材料等相关学科的多尺度理论研究提供新思路。研究结果可为海底管道的安全运行和面向腐蚀设计提供依据。

点腐蚀是导致海底管道等装置失效的主要原因，腐蚀点的多尺度随机演变是腐蚀机理和预测研究中的重要问题。已有研究集中在单个腐蚀点形成机制或点腐蚀的宏观表现，缺乏有关点蚀群随机演化的深入研究，大规模点蚀群演化的实验研究未见报道。本项目通过腐蚀浸泡实验、电化学测试、高分辨大视场三位光学显微观察等手段，研究了典型高强度管线钢在含氯腐蚀溶液中的腐蚀初期点腐蚀群分布和演化规律，获得了典型腐蚀点的高清三维结构、揭示了点腐蚀群空间统计分布规律及其与空间尺度的相关性，捕捉到了点腐蚀群由小尺度下的随机分布向大尺度聚类分布转化的现象；建立了腐蚀中期腐蚀产物与电化学阻抗信号的定量关系，通过设计不同样品表面取向的腐蚀原位电化学测试，定量揭示了腐蚀产物对高强钢腐蚀速率和局部腐蚀点演化的影响规律；进一步深入研究了腐蚀阴极反应可能产生的氢致开裂问题，以高强度压力容器用钢为例，研究了氢致鼓泡、氢致裂纹与氢浓度之间的关系，获得了氢致裂纹的三维结构，发现了氢致鼓泡下裂纹深度与长度比与氢浓度强相关的现象，间接证明了裂纹扩展过程中裂纹内氢气压力动态升高机制。项目主要成果在国际学术期刊发表SCI论文3篇。