金属再钝化暂态电化学响应规律和再钝化膜稳定性研究

The repassivation quality of metal determines its capability to resist corrosion, and it's also closely related to different corrosion forms. However, the repassivation process and the stability of repassivation film have not been well interpreted. Herein, the transient characteristics of repassivation process and the stability of repassivation film will be studied thoroughly. Therefore, a novel equipment for repassivation film removing has been designed and manufactured, and the in situ electrochemical detection techniques with high speed and accuracy will be employed to explore the relationship of the stability of repassivation film, the structure and tissue, and the environment, focusing on multiscacle characteristics of repassivation process standing on the points of duration and the signal response. Analytical method for high speed and accurate electrochemical signal response during the repassivation process is expected to be developed on the bases of the mentioned research. For the sake of explaining the structure-activity relationship between the stability of repassivation film and its environment, the X-ray absorption fine structure (XAFS) and the X-ray Photoelectron Spectroscopy(XPS) will be introduced to investigate the structure and tissue.Subsequently, the kinetic models of repassivation process will be established, and a series of criterion and characterization method for stability of repassivaton film will be proposed.

金属再钝化性能优劣决定了其耐蚀性能的差异，并且与多种腐蚀形式密切相关。但目前国内外对再钝化过程和再钝化膜稳定性的研究还存在不足之处。本项目将围绕金属再钝化过程的暂态特性和再钝化膜的稳定性两个关键问题，针对再钝化过程在持续时间、响应信号上的多尺度特征，再钝化膜稳定性与组织结构、环境之间交叉相关的特点，采用自行设计制造的新型机械去膜装置、高速高精电化学响应信号原位检测技术，探索金属再钝化演变过程在不同时间尺度上响应信号的变化特征和相互联系，建立再钝化高速高精电化学响应信号的解析方法；借助同步辐射光源X射线吸收精细结构谱、光电子能谱等先进的表面分析方法，研究并发现再钝化膜稳定性与结构、环境之间的构效关系和对应规律。建立再钝化过程的动力学模型和再钝化膜稳定性的表征方法及判据。

金属再钝化性能优劣决定了其耐蚀性的差异，并且与多种腐蚀形式密切相关，但是目前国内外对再钝化过程和再钝化膜稳定性的研究还存在不足。本项目围绕这两个关键问题，开展了再钝化过程多尺度电化学响应特征与规律、再钝化膜稳定的电化学判据与影响因素和再钝化膜组织结构特征与稳定性关系的研究。.第一，利用新型电极擦伤技术研究了9种材料在7种腐蚀介质中的再钝化暂态电化学信号响应规律，建立了普适动力学模型将暂态过程分为三个阶段。对于316L不锈钢的再钝化响应信号，建立了数字化解析模型Itol=Idiss+Ifilm。对于从ms到120 h的再钝化稳定化过程，建立了衰减模型，并研究了电位和Cl-浓度的影响规律，提出了金属阳极极化的普适分区新方法。.第二，研究了5种材料、3类腐蚀介质（氯离子浓度、pH、氧化还原性）和3种外场条件（温度场、力学场、磁场）对的再钝化膜稳定稳定性的影响规律，建立了2项普适的电化学判据：电流-时间衰减速率Dr减小至10-13 Acm-2s-1时，或者再钝化膜中间隙金属离子或氧空位的扩散系数DO减小至10-18 cm2s-1时，认为钝化膜接近稳态。.第三，采用同步辐射XANES、EXAFS、XPS、AES、原位椭圆偏振光谱技术、EIS、计时电流和阻抗-电位等技术从微观组织结构入手，研究了时间序列、外在条件（材料、腐蚀介质、外场电位）和内在条件（结合水）对再钝化膜稳定性的作用规律并建立构效关系。合金元素再钝化过程中形核速度不同，Cr的形核速度远大于Fe和Ni；Ti-O的平均配位数的增加引起了金属Ti钝化，而Ti-Ti原子间距的微弱畸变引起了钝化膜的溶解。.本项目开展了对再钝化过程电化学响应的数字化解析，对腐蚀基础理论进行了关键的补充和完善；稳态电化学判据的构建，为材料腐蚀寿命预测提供了的科学依据；构效关系的建立，拓展了腐蚀理论和耐蚀新材料的研发思路，意义重大；另外，多因素交互外场耦合作用的全面研究，对于复杂多变环境中材料的腐蚀防护具有重要的工程实践指导意义。