Visser Peter, Liu Yanwen, Zhou Xiaorong, Hashimoto Teruo, Thompson George E, Lyon Stuart B, van der Ven Leendert G J, Mol Arjan J M C, Terryn Herman A
Delft University of Technology, Department of Materials Science and Engineering, Delft, The Netherlands.
Faraday Discuss. 2015;180:511-26. doi: 10.1039/c4fd00237g.
Lithium carbonate and lithium oxalate were incorporated as leachable corrosion inhibitors in model organic coatings for the protection of AA2024-T3. The coated samples were artificially damaged with a scribe. It was found that the lithium-salts are able to leach from the organic coating and form a protective layer in the scribe on AA2024-T3 under neutral salt spray conditions. The present paper shows the first observation and analysis of these corrosion protective layers, generated from lithium-salt loaded organic coatings. The scribed areas were examined by scanning and transmission electron microscopy before and after neutral salt spray exposure (ASTM-B117). The protective layers typically consist of three different layered regions, including a relatively dense layer near the alloy substrate, a porous middle layer and a flake-shaped outer layer, with lithium uniformly distributed throughout all three layers. Scanning electron microscopy and white light interferometry surface roughness measurements demonstrate that the formation of the layer occurs rapidly and, therefore provides an effective inhibition mechanism. Based on the observation of this work, a mechanism is proposed for the formation of these protective layers.
碳酸锂和草酸锂作为可浸出的缓蚀剂被添加到用于保护AA2024-T3的模型有机涂层中。对涂覆的样品用划格法进行人工损伤。研究发现，在中性盐雾条件下，锂盐能够从有机涂层中浸出，并在AA2024-T3的划格处形成一层保护膜。本文首次展示了对由负载锂盐的有机涂层生成的这些腐蚀防护层的观察和分析。在中性盐雾暴露（ASTM-B117）前后，通过扫描电子显微镜和透射电子显微镜对划格区域进行了检查。防护层通常由三个不同的分层区域组成，包括靠近合金基体的相对致密层、多孔中间层和片状外层，锂在所有三层中均匀分布。扫描电子显微镜和白光干涉表面粗糙度测量表明，该层的形成迅速，因此提供了一种有效的抑制机制。基于这项工作的观察结果，提出了这些防护层形成的机制。
