层状纳米孪晶镍镀层的形成机制及耐Cl-腐蚀机理

Focusing on the current core issue about nanocrystalline metallic materials with low corrosion resistance and uneven corrosion, under the guidance of grain boundary design and control, new electrodeposition crystallization theory, nickel coating with laminated nanotwins was prepared by flexible friction-assisted electrodeposition technology. Under different friction force-electrochemical synergy, the structural characteristics distribution of nanotwins, lamellar thickness, stress evolution, etc. was observed. Combined with nucleation and growth of nano-twins by in-situ electrochemical measurements, the formation law and formation mechanism of flexible friction-assisted electroplated nickel coating with laminated nanotwins was clarified. The electrochemical property and electrochemical performance analysis of the typical nano-twinned nickel coating with different nanotwins density and different thicknesses was studied by means of electrochemical workstation, scanning Kelvin probe (SKP) and scanning electrochemical microscopy (SECM) etc. methods. Combined with their macro and micro corrosion characteristics and corrosion behavior in containing Cl- environment, the penetration path and propagation regulation of corrosive media along cross-section direction of the coating was described. Finally, the corresponding corrosion model and corrosion mechanism will be established and revealed in containing Cl- environment, respectively. The research results have important theoretical and practical value for nanocrystalline metallic materials to the achievement of long-term protection project.

针对目前纳米晶金属材料耐蚀性不高和腐蚀不均匀的核心问题，在晶界设计和控制以及电沉积结晶新理论的指导下，采用柔性摩擦辅助电沉积技术制备层状纳米孪晶镍镀层。通过观察不同摩擦外力-电化学作用下的纳米孪晶特征分布、层状厚度、应力演变等情况，结合原位电化学测量的纳米孪晶形核和生长结果，阐明柔性摩擦辅助电沉积层状纳米孪晶镍镀层的形成规律和形成机制；采用扫描开尔文探针(SKP)、扫描电化学显微镜(SECM)和电化学工作站等手段对典型不同纳米孪晶密度和不同层状厚度的镍镀层进行电化学性质和电化学性能分析，结合其在Cl-环境中的宏、微观的腐蚀特征和腐蚀行为，描述腐蚀介质沿镀层截面方向的渗透和扩展规律，最终建立相应的腐蚀模型，并揭示其在Cl-环境中的腐蚀机理。该研究成果对实现纳米晶金属材料的长效防腐工程具有重要的理论和应用价值。

针对目前纳米晶金属材料耐蚀性不高和腐蚀不均匀的核心问题，采用柔性摩擦辅助电沉积技术在不含任何添加剂的Watts镀液中制备层状纳米孪晶镍镀层，并阐明形成机制及其在非钝化Cl-环境中的腐蚀机理。结果表明，在较高的电流密度，高的镀液温度以及大的摩擦压力条件下，有利于制备高密度的纳米孪晶镍镀层；柔性摩擦能够打破电结晶过程中吸附原子间的聚集生长，并周期性抑制晶体快速生长，导致晶粒尺寸更细和界面应力更高，使得结晶弛豫过程中形成大量层状的纳米孪晶；该结构在含Cl-的腐蚀环境中增加了腐蚀介质的扩展路径，使腐蚀过程逐层进行，腐蚀介质难以快速到达基体表面，从而降低了腐蚀电流密度，并改善了基体的防护性能。该研究成果对实现纳米晶金属材料的长效防腐工程应用具有重要的指导意义。