镁合金电偶腐蚀破坏的负差数放大效应及对策研究

Mg alloys are important lightweight materials concerning the reduction of energy consumption and environment protection in the manufacturing industry (e.g., the automobile). Their successful application in practice is critical to the upgrading of high-techs in national security related fields, such as the aerospace and military. Unfortunately, corrosion has been one of the most serious problems limiting their uses in these areas so far. The most commonly observed damage of Mg alloys is galvanic corrosion, which is an anodic dissolution process of the alloys accelerated by other engineering metals in contact through the well-known galvanic effect. Behind the apparent damage is actually an exacerbation process of the galvanic corrosion by the negative difference effect (NDE). Such an all exacerbation effect has never been reported. A comprehensive investigation into the NDE-significantly-worsened galvanic corrosion is the key to understanding the electrochemical mechanism of Mg corrosion. It can lay a theoretical foundation for galvanic corrosion modeling and establish an experimental database for optimization of corrosion prevention techniques for Mg alloys in practice. More importantly, the gained knowledge regarding the galvanic corrosion exacerbation can serve as a design guide to development of corrosion resistant Mg alloys. In this proposed study, to understand the exacerbation of galvanic corrosion by the negative difference effect of Mg alloys, 4 different fundamental fields will be explored: the exacerbation mechanism of Mg galvanic corrosion, the secondary effect of corrosion products on the exacerbation behavior, the involvement of alloying elements in the exacerbated galvanic corrosion of Mg matrix phase, and the possibility of surface alloying to passivate Mg alloys in order to mitigate their galvanic corrosion. Through utilizing a recently developed technique, Tunneling Electronic Microscope Assisted Scanning Electrochemical Probe (TEM-SECP) and magnetron-sputtering-produced non-equilibrium Mg alloys and their array sensor, the electrochemical reactions involved in the anodic dissolution of Mg in some local surface areas will be clarified, and the galvanic corrosion behavior of Mg alloys will be better understood to a new theoretical depth. The research will also bring insight into the practical galvanic corrosion damage from a new perspective considering the secondary effect of corrosion products as a critical influencing factor. Based on the new theory of galvanic corrosion exacerbated by negative difference effect, the preferential dissolution of the Mg matrix phase in the Mg alloy will be reasonably predicted. After the exacerbation of galvanic corrosion by the negative difference effect on Mg alloys is comprehensively understood, practically effective corrosion prevention techniques (e.g., surface burnishing assisted hot-diffusion surface alloying to enhance the passivity and mitigate the galvanic corrosion) for Mg alloys will be developed, which may eventually lead to solution of the corrosion problem of Mg alloys.

电偶腐蚀是公认的镁工程应用最主要障碍之一。所伴随的负差数效应使镁合金的电偶腐蚀被“异常”放大，呈“反常”分布，难以预测防范。导致这一工程难题的科学原因是其阳极溶解负差数放大效应的机理不明。澄清这一科学前沿争议论题，可为镁合金防腐措施优化和耐蚀镁合金设计提供理论依据。本项目围绕着从工程应用中提炼出来的镁合金电偶腐蚀负差数放大效应这一科学问题，以探明其阳极溶解机理、次生放大作用、合金元素影响、表面合金化层钝性为目标，以镁列阵电极与隧道显微镜辅助扫描电化学探针相结合的新手段、磁控溅射镁合金“千层饼”阵列电极的新方法、表面磨光微晶/纳米晶化促进扩散合金化的新工艺作为特色技术，辅以腐蚀、电化学、表面分析等常规实验，澄清镁合金阳极溶解过程中的局部阴极电流争议，建立负差数放大效应模型，掌握次生效应影响规律，确定最佳抗电偶腐蚀的合金化元素，开发最有效表面合金技术，揭示镁腐蚀本质，促进其电偶腐蚀问题的解决。

电偶腐蚀是公认的镁合金工程应用最主要障碍之一。所伴随的负差数效应使镁合金的电偶腐蚀破坏被“异常”放大，呈“反常”分布，难以预测防范。导致这一工程难题的科学原因是其阳极溶解负差数放大效应的机理不明。澄清这一科学前沿争议论题，可为镁合金防腐措施优化和耐蚀镁合金设计提供理论依据。本项目围绕着从工程应用中提炼出来的镁合金电偶腐蚀负差数放大效应这一科学问题，以探明其阳极溶解机理、次生放大作用、合金元素影响、表面合金化层钝性为目标，以镁列阵电极与隧道显微镜辅助扫描电化学探针相结合的新手段、磁控溅射镁合金“千层饼”阵列电极的新方法、表面磨光微晶/纳米晶化促进扩散合金化的新工艺作为特色技术，辅以腐蚀、电化学、表面分析等常规实验，澄清镁合金阳极溶解过程中的局部阴极电流争议，建立负差数放大效应模型，掌握次生效应影响规律，优化抗电偶腐蚀方法，开发有效表面合金化技术，揭示镁腐蚀本质，促进其电偶腐蚀问题的解决。