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Development of nanostructured coatings for protecting the surface of aluminum alloys against corrosion and ice accretion =

机译：开发用于保护铝合金表面不腐蚀和不结冰的纳米结构涂层=

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摘要

Ice and wet snow accretion on outdoor structures is a severe challenge for cold climate countries. A variety of de-icing and anti-icing techniques have been developed so far to counter this problem. Passive approaches such as anti-icing or icephobic coatings that inhibit or retard ice accumulation on the surfaces are gaining in popularity.;Metal corrosion should also be taken into account as metallic substrates are subject to corrosion problems when placed in humid or aggressive environments. Development of any ice-releasing coatings on aluminum structures, as they must be durable enough, is therefore closely related to anti-corrosive protection of that metal.;Accordingly, series of experiments have been carried out to combine reduced ice adhesion and improved corrosion resistance on flat AA2024 substrates via thin films of single and double layer alkyl-terminated SAMs coatings. More precisely, alkyl-terminated aluminum substrates were prepared by depositing layer(s) of 18C-SAMs on BTSE-grafted AA2024 or mirror-polished AA2024 surfaces. This alloy is among the most widely used aluminum alloys in transportation systems (including aircraft), the military, etc. The stability of the coatings in an aggressive environment, their overall ice-repellent performance as well as their corrosion resistance was systematically studied.;The stability of one-layer and two-layer coatings in different media was tested by means of CA measurements, demonstrating gradual loss of the hydrophobic property after ~1100-h-long immersion in water, associated by decrease in water CA. Surface corrosion was observed in all cases, except that the double-layer coating system provided improved anti-corrosive protection.;All single layer coatings showed initial shear stress of ice detachment values of ~1.68 to 2 times lower than as-received aluminum surfaces and about ~1.22 to 1.5 times lower than those observed on mirror-polished surfaces. These values gradually increased after as many as 5 to 9 successive icing/de-icing cycles, implying a certain amount of decay of the coatings. The double-layer coating system initially showed shear stress of ice detachment values about ~2 times lower than as-received aluminum surfaces and ~1.5 times lower than those observed on mirror-polished aluminum surfaces as references. These values gradually increased after as many as 9 successive icing/de-icing cycles.;In addition, the hydrophobic property of coated surfaces was investigated after the icing/de-icing cycle to study their stability after ice releasing, showing therein a decrease in CA values. As a result, the ice-releasing performance of coated samples was found to be time-dependent. The electrochemical studies demonstrated that the corrosion potential of samples covered by single layer hydrophobic coatings increased slightly while their corrosion current density decreased as compared to bare substrate. However, the corrosion potential of samples covered by double-layer hydrophobic coatings increased significantly, and their corrosion current density decreased by 4 orders of magnitude as compared to those on the uncoated samples. These results showed that the used under layer on AA2024 provides particularly enhanced corrosion resistance which would be an excellent approach to improve the anti-corrosive performance of metallic surfaces for outdoor application instead of current-in-use toxic chromate-based coatings. In addition, the electrochemical impedance spectroscopy survey showed a higher phase angle and thus a lower ionic permeation for the double layer coating system, leading to a better insulating property of that coating. These evidences confirm that the BTSE/18C-SAMs behaves close to an ideal capacitor compared to 18C-SAMs alone, as a leaky capacitor. On the other hand, based on results obtained from total impedance vs. frequency, the impedance values are higher for double layer coating compared to single coating, indicating thereby a more packed film with fewer defects.;Finally, this research work revealed the feasibility of preparing coatings combining reduced adhesion of ice to aluminum surfaces and protection against corrosion.
机译：对于寒冷气候国家来说，在室外建筑物上积聚冰和湿雪是严峻的挑战。迄今为止，已经开发出多种除冰和防冰技术来解决该问题。抑制或阻止冰在表面上积聚的无源方法（例如防冰或憎冰涂层）正变得越来越流行。金属腐蚀也应考虑在内，因为金属基材在潮湿或腐蚀性环境中会遇到腐蚀问题。因此，在铝结构上开发任何防冰涂层，因为它们必须足够耐用，因此与该金属的防腐蚀保护密切相关。因此，已进行了一系列实验，以减少冰的附着力并提高耐腐蚀性。通过单层和双层烷基封端SAMs涂层的薄膜在平坦的AA2024基板上涂覆。更精确地，通过在BTSE接枝的AA2024或镜面抛光的AA2024表面上沉积18C-SAMs层来制备烷基封端的铝基材。该合金是运输系统（包括飞机），军用等领域中使用最广泛的铝合金之一。系统地研究了涂层在侵蚀性环境中的稳定性，整体防冰性能以及耐腐蚀性。通过CA测量测试了一层和两层涂层在不同介质中的稳定性，证明了在水中浸泡约1100小时后疏水性能逐渐丧失，这与水CA降低有关。在所有情况下均观察到表面腐蚀，除了双层涂层体系提供了更好的防腐蚀保护外;所有单层涂层均显示出冰分离值的初始剪切应力比原铝表面低约1.68至2倍，并且比镜面抛光表面低约1.22至1.5倍。这些值在经过多达5到9个连续的除冰/除冰循环后逐渐增加，这意味着涂层会有一定程度的衰减。双层涂层系统起初显示出冰分离的剪切应力值比原铝表面低约2倍，比镜面抛光铝表面低约1.5倍。这些值在经过多达9个连续的结冰/除冰循环后逐渐增加。;此外，在结冰/除冰循环后对涂层表面的疏水性进行了研究，以研究其在冰释放后的稳定性，表明其中冰的减少。 CA值。结果，发现涂覆样品的除冰性能是时间依赖性的。电化学研究表明，与裸露的基材相比，被单层疏水涂层覆盖的样品的腐蚀电位略有增加，而腐蚀电流密度却降低了。然而，与未涂覆样品相比，被双层疏水涂层覆盖的样品的腐蚀电位显着增加，并且其腐蚀电流密度降低了4个数量级。这些结果表明，AA2024上使用的底层提供了特别增强的耐腐蚀性，这将是一种很好的方法，可以改善用于室外应用的金属表面的防腐蚀性能，而不是目前使用的有毒铬酸盐基涂料。此外，电化学阻抗谱调查显示双层涂层系统的相角较高，因此离子渗透率较低，从而导致该涂层的绝缘性能更好。这些证据证实，与作为漏电电容器的18C-SAM相比，BTSE / 18C-SAM的性能接近理想电容器。另一方面，根据总阻抗与频率的关系，双层涂层的阻抗值要高于单层涂层，这表明薄膜的填充量更大，缺陷更少。制备涂料，将减少的冰与铝表面的附着力并防止腐蚀。

著录项

  • 作者

    Farhadi, Shahram.;

  • 作者单位

    Universite du Quebec a Chicoutimi (Canada).;

  • 授予单位 Universite du Quebec a Chicoutimi (Canada).;
  • 学科 Chemical engineering.;Materials science.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 198 p.
  • 总页数 198
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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