Corrosion Monitoring for Deep Underground Environment

材料表面形成了块体与环境的界面，并表现出不同于块体材料的各种性质。金属和合金表面的氧化物薄膜将内部材料与环境隔离，防止环境退化，并显示出与环境相互作用的各种化学和物理功能。在水溶液中，材料表面通过各种相互作用形成独特的表面层，呈现出新的化学成分、有序的结构和功能。本工作利用光电化学响应和电化学阻抗谱研究了镍和镍铬合金、铁铬合金的光辐照改性，以及与光诱导修饰密切相关的钝化膜的电学性质。垫子…更多的材料在不同电位下的0.1kmolm~(-3)H_2SO_4中极化24小时。测量了单色光照射产生的光电流和从成膜电位开始的一系列非贵金属方向的电势的电化学阻抗电容。用XPS对钝化膜进行了表征，并用电化学阻抗谱和光电化学方法研究了Fe-18Cr在中性硼酸盐缓冲液中形成的钝化膜。钝化膜由内氧化层和覆盖氢氧化层组成，两者均为n型半导体，带隙能分别为3.4-3.5 eV和2.4 eV。在实验结果的基础上，考虑XPS假设的薄膜结构，提出了双层半导体的电子能带结构模型。文中还讨论了光照射引起的能带结构的变化，从而导致了光电流瞬变和空间电荷层电容的变化。从膜生长动力学和腐蚀过程两个方面讨论了Fe-Cr合金在中性溶液和酸性溶液中形成的钝化膜的差异。较少

The surface of materials forms interface between bulk and environment, and exhibits various properties that are different from that of bulk material. Surface thin oxide films on metals and alloys isolate the internal materials from environment to prevent environmental degradation, and exhibit various chemical and physical function as interaction between environment. Using aqueous solution process, surface of materials is modified by various interactions to produce unique surface layer, exhibiting new chemical composition, ordered structure, functions.In the present work, modification of Ni and Ni-Cr alloys, Fe-Cr alloys by light irradiation, and electronic properties of passive film which is highly related with the light induced modification are discussed using photo electrochemical response and electrochemical impedance spectroscopy.Properties of passive films on Ni and Ni-18Cr formed in acid solution are characterised in order to discuss semiconductor properties of passive films. Mat … More erials were polarised in deaerated 0.1 kmol m-3 H2SO4 at various potentials for up to 24 hours. Photo current generated by irradiation of monochromated light, and capacitance by means of electrochemical impedance were measured for a series of potentials in less noble direction from the film formation potential. The passive films were also characterised using XPS.Passive film on Fe-18Cr formed in the neutral borate buffer solution was studied using an electrochemical impedance spectroscopy and a photo electrochemical response. The passive film is composed of inner oxide and covering hydroxide layer, both which exhibit n-type semiconductor property with band gap energy, Eg, of 3.4-3.5 eV and 2.4 eV, respectively. Electronic energy band structure model as bi-layer semiconductor was proposed based on the experimental results, considering the film structure presumed by XPS. The change of energy band structure by photo irradiation is also discussed which results in photo current transient and change in capacitance of space charge layer. The difference between passive film on Fe-Cr alloys formed in the neutral and acid solution was also discussed in terms of film growth kinetics and corrosion process. Less