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Relation between the semiconducting properties of passive films and electrochemical and corrosion properties.

机译：钝化膜的半导体性能与电化学和腐蚀性能之间的关系。

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摘要

Aqueous corrosion is a common materials degradation mechanism and is thought to be a likely failure mode of high level nuclear waste canisters. Corrosion damage is often mitigated by a protective oxide film that forms naturally on many metals. The semiconducting properties of these films often have a large impact on the electrochemical and corrosion behavior of metal-passive film systems.;In this study the flatband potential and charge carrier density of the films that form on Alloy C22, Cr, Ti, Fe, Ni, Mo and mild steel were evaluated by Mott-Schottky analysis. All films with the exception of Ni oxide were n-type at all measured frequencies. The calculation of the flatband potentials and charge carrier densities was complicated by measured capacitances that were frequency dependent. A new method was proposed to fit the frequency dispersion with a Constant Phase Element (CPE) and then expressions developed by Brug et al. [J. Electroanal. Chem., 176, 275 (1984)] or Hsu and Mansfeld [Corrosion, 57, 747 (2001)] were used calculate effective capacitances as a function of potential. The success of this method was evaluated using cathodic polarization tests. Flatband potentials calculated using Brug et al.'s expression were in excellent agreement with the onset potential of reduction current growth in polarization scans.;It was found that films with more negative flatband potentials were less susceptible to localized attack due to the slower reduction kinetics associated with low flatband potentials. Alloy C22 has a very negative flatband potential and is highly resistant to localized corrosion at room temperature but improved reduction kinetics at elevated temperature contributes to Alloy C22's susceptibility to metastable pitting at high temperatures.
机译：水腐蚀是一种常见的材料降解机制，并且被认为是高级核废料罐的一种可能的失效模式。腐蚀损伤通常可以通过在许多金属上自然形成的保护性氧化膜来减轻。这些薄膜的半导体性能通常会对金属钝化薄膜系统的电化学和腐蚀行为产生重大影响。在本研究中，在C22，Cr，Ti，Fe， Ni，Mo和低碳钢通过Mott-Schottky分析进行评估。除氧化镍外，所有薄膜在所有测量频率下均为n型。由于测得的电容与频率有关，因此平带电势和电荷载流子密度的计算变得很复杂。提出了一种新的方法，以使频率色散与恒定相位元素（CPE）相匹配，然后由Brug等人开发。 [J.电子肛门。 Chem。，176，275（1984）]或Hsu和Mansfeld [Corrosion，57，747（2001）]用于计算有效电容量与电势的关系。使用阴极极化测试评估了该方法的成功。使用Brug等人的表达式计算出的平带电势与极化扫描中还原电流增长的开始电势非常吻合;发现具有较差的平带电势的薄膜由于还原动力学较慢而较不易受到局部腐蚀的影响与低平坦带电位有关。合金C22具有非常负的平坦带电势，并且在室温下对局部腐蚀具有很高的抵抗力，但是高温下还原动力学的改善有助于合金C22在高温下对亚稳点蚀的敏感性。

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  • 作者

    Harrington, Scott Peter.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 181 p.
  • 总页数 181
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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