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首页> 外文学位 >Chromate-free corrosion inhibition of aluminum alloys: Vanadates and anionic exchange clay pigments.
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Chromate-free corrosion inhibition of aluminum alloys: Vanadates and anionic exchange clay pigments.

机译：铝合金的无铬酸盐腐蚀抑制：钒酸盐和阴离子交换粘土颜料。

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摘要

In this study, aqueous vanadates and vanadate pigments were studied for possible use as chromate replacements to inhibit corrosion of Al 2024-T3. Vanadate inhibition on Al 2024-T3 was characterized as a function of pH and concentration using anodic and cathodic polarization experiments and scanning electron microscopy (SEM). The results showed a strong correlation between inhibition and the availability of tetrahedrally coordinated vanadate species in test solutions. In particular, solutions containing predominately tetrahedrally coordinated vanadates were observed to act as modest anodic inhibitors and to reduce cathodic kinetics through the suppression of oxygen reduction kinetics. Further, the effect of these tetrahedral vanadates on individual intermetallic particles commonly found in Al 2024-T3 was characterized using a microcapillary electrode. Tetrahedral vanadates were generally found to increase breakdown potentials and decrease cathodic kinetics on all tested materials. Open circuit potential (OCP) was observed to shift in the active direction as a result of decreased cathodic kinetics, just below the observed breakdown potential of Al2CuMg; a phase that plays a critical role in corrosion susceptibility of Al 2024-T3. OCP measurements, SEM images, and potentiostatic hold experiments were used to show suppressed Al2CuMg dissolution and damage accumulation in vanadate solutions.;Furthermore, synthetic hydrotalcite anion exchange clay pigments were synthesized with vanadates and other possible inhibitor anions. Hydrotalcites allow the use of inhibitors that are too soluble for direct use in organic coatings without leading to coating blistering. A number of hydrotalcite pigments were synthesized and compared to a SrCrO4 standard using electrochemical impedance spectroscopy and salt spray exposure of scribed organically coated panels. Typically, vanadate pigmented PVB coatings were observed to have total impedance within an order of magnitude of SrCrO4 (2 x 10 7 ohms cm2). Further, all vanadate coatings were observed to provide some scribe protection during 750 hours of salt spray exposure, however, these coatings also had a tendency to blister. Release from vanadate hydrotalcites was characterized using neutron activation analysis. Interestingly, vanadate hydrotalcite pigments that released relatively small total concentrations of vanadium resulted in the best performance. Low concentrations of vanadium may promote the formation of tetrahedrally coordinated species which were shown to act as inhibitors earlier in this study.
机译：在这项研究中，研究了水性钒酸盐和钒酸盐颜料可能用作铬酸盐的替代品，以抑制Al 2024-T3的腐蚀。使用阳极和阴极极化实验以及扫描电子显微镜（SEM），表征了钒酸盐对Al 2024-T3的抑制作用与pH和浓度的关系。结果表明，抑制作用与测试溶液中四面体配位的钒酸盐物种的可用性之间存在很强的相关性。特别地，观察到主要含有四面体配位的钒酸盐的溶液充当适度的阳极抑制剂并通过抑制氧还原动力学而降低阴极动力学。此外，使用微毛细管电极表征了这些四面体钒酸盐对Al 2024-T3中常见的单个金属间颗粒的影响。通常发现四面体钒酸盐会增加所有测试材料的击穿电位并降低阴极动力学。由于阴极动力学降低，观察到开路电势（OCP）向着活动方向移动，刚好低于所观察到的Al2CuMg的击穿电势。在Al 2024-T3的腐蚀敏感性中起关键作用的相。用OCP测量，SEM图像和恒电位保持实验显示了钒酸盐溶液中Al2CuMg的溶解受到抑制和损伤积累。此外，合成了水滑石阴离子交换粘土颜料与钒酸盐和其他可能的抑制剂阴离子。水滑石允许使用太易溶解的抑制剂而不能直接用于有机涂料中而不会导致涂料起泡。合成了许多水滑石颜料，并将其与SrCrO4标准品进行了比较，方法是使用电化学阻抗谱和划线的有机涂层面板进行盐雾暴露。通常，观察到钒酸盐着色的PVB涂层的总阻抗在SrCrO4（2 x 10 7 ohms cm2）的数量级内。此外，观察到所有钒酸盐涂层在盐雾暴露的750小时期间均提供了某种划痕保护，但是，这些涂层也具有起泡的趋势。使用中子活化分析来表征从钒酸盐水滑石中释放。有趣的是，释放出相对较低的钒总浓度的钒酸盐水滑石颜料具有最佳性能。低浓度的钒可能会促进四面体配位物种的形成，在本研究的早期，钒被证明是抑制剂。

著录项

  • 作者

    Ralston, Kevin Douglas.;

  • 作者单位

    The Ohio State University.;

  • 授予单位 The Ohio State University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 258 p.
  • 总页数 258
  • 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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