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首页> 外文学位 >Mapping Local Corrosion Parameters Using SVET and SIET =Mapeamento de parâmetros locais de corrosão usando SVET e SIET
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Mapping Local Corrosion Parameters Using SVET and SIET =Mapeamento de parâmetros locais de corrosão usando SVET e SIET

机译：使用SVET和SIET映射局部腐蚀参数=使用SVET和SIET映射局部腐蚀参数

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摘要

Localized corrosion, i.e., corrosion confined to local regions, is difficult to predict and control. In general, it appears as a result of heterogeneities, either in the metal or in the corrosive environment. One of the phenomenological features of localised corrosion is the development of specific environments close to active sites. In practice, the micro-environment near the metallic surface is different from that of the bulk medium and varies with time and conditions of the system under study. Localized electrochemical techniques based on the use of microelectrodes are well suited for in situ sensing the distribution of potential, current and chemical species in active zones, pores or defects. Most of the published work dealing with microelectrodes in corrosion is mainly exploratory and their use in a regular basis is still rare in corrosion research. This work presents the development and application of microelectrodes as experimental tools capable to assess local electrochemical reactions on metallic substrates immersed in aggressive solutions. Traditional electrochemical techniques used in corrosion research give the average response of the global activity of the whole surface not discriminating local effects and local chemistry. Therefore they are unable per si to properly characterize localized phenomena and the corresponding corrosion, inhibitive mechanisms and, sometimes, even to select the best protection methods. It is important to know local parameters such as pH, micro-galvanic effects, concentration of oxidizing (like O2) and aggressive (like Cl-) species, and formation of surface films. The Scanning Vibrating Electrode Technique (SVET) was used for local measurements of ionic currents in solution. The technique detects the potential distribution in solution associated to ionic currents in solution. For the analysis of the chemical species involved in the corrosion process, electrochemical microsensors were used in SIET (Scanning Ion Selective Electrode Technique) mode. Microelectrodes sensitive to pH, dissolved oxygen and metal cations (namely, Mg2+, Zn2+ and Cu2+) were developed and characterized. Work was also done with microeloectrodes sensitive to Al3+, but with less success. Then, they were used for investigating the reactivity on defects and corrosion inhibition on coated aluminium and magnesium alloys, detecting the micro-distribution of chemical species in solution close to the corroding surface of Zn, Cu and a Zn- Fe galvanic couple specimens. ix Limitations and difficulties exist for the use of these techniques in corrosion research due to the inherent reactivity of corroding metals, with the formation of corrosion products and sharp changes of pH, O2 and ionic strength along the samples surface. In spite of the difficulties, the results presented here demonstrate that the SVET/SIET mapping gives useful information for the quantification of electrochemical processes at the micro-level. The data are of prime importance for the modelling and simulation of corrosion mechanisms, selection of new corrosion inhibitors and development of ''smart" coatings that suppress the corrosion processes.
机译：局部腐蚀，即局限于局部腐蚀，很难预测和控制。通常，它是由于金属或腐蚀环境中的异质性而出现的。局部腐蚀的现象学特征之一是靠近活动部位的特定环境的发展。在实践中，金属表面附近的微环境不同于本体介质的微环境，并且随所研究系统的时间和条件而变化。基于使用微电极的局部电化学技术非常适合于现场检测活性区，孔或缺陷中的电势，电流和化学物质的分布。有关腐蚀中微电极的大多数已发表的工作主要是探索性的，在腐蚀研究中仍很少定期使用它们。这项工作介绍了微电极的开发和应用，作为能够评估浸入侵蚀性溶液的金属基材上的局部电化学反应的实验工具。腐蚀研究中使用的传统电化学技术给出了整个表面的总体活性的平均响应，而不区分局部效应和局部化学性质。因此，它们本身无法正确地表征局部现象和相应的腐蚀，抑制机制，有时甚至无法选择最佳的保护方法。重要的是要知道局部参数，例如pH值，微电流效应，氧化（如O2）和侵蚀性（如Cl-）物种的浓度以及表面膜的形成。扫描振动电极技术（SVET）用于溶液中离子电流的局部测量。该技术检测溶液中与溶液中离子电流相关的电位分布。为了分析腐蚀过程中涉及的化学物质，以SIET（扫描离子选择电极技术）模式使用了电化学微传感器。开发并表征了对pH，溶解氧和金属阳离子（即Mg2 +，Zn2 +和Cu2 +）敏感的微电极。还对敏感的Al3 +进行了微电杆的研究，但成功率较低。然后，它们被用于研究涂层和铝合金上缺陷的反应性和缓蚀性能，检测溶液中接近Zn，Cu和Zn-Fe电偶试样的腐蚀表面的化学物种的微观分布。 ix由于腐蚀金属的固有反应性，腐蚀产物的形成以及沿着样品表面的pH，O2和离子强度的急剧变化，在腐蚀研究中使用这些技术存在局限性和困难。尽管存在困难，但此处显示的结果表明SVET / SIET映射为微观水平的电化学过程定量化提供了有用的信息。数据对于腐蚀机理的建模和仿真，新腐蚀抑制剂的选择以及抑制腐蚀过程的“智能”涂层的开发至关重要。

著录项

  • 作者

    Karavai, Olga.;

  • 作者单位

    Universidade de Aveiro (Portugal).;

  • 授予单位 Universidade de Aveiro (Portugal).;
  • 学科 Engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 242 p.
  • 总页数 242
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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