São Paulo State University (UNESP) , Institute of Chemistry , 14800-060 Araraquara , São Paulo , Brazil.
Vrije Universiteit Brussel , Department of Materials and Chemistry, Research Group of Electrochemical and Surface Engineering , Pleinlaan 2 , 1050 Brussels , Belgium.
ACS Appl Mater Interfaces. 2019 Oct 30;11(43):40629-40641. doi: 10.1021/acsami.9b13839. Epub 2019 Oct 18.
In this work, structural and active corrosion inhibition effects induced by lithium ion addition in organic-inorganic coatings based on poly(methyl methacrylate) (PMMA)-silica sol-gel coatings have been investigated. The addition of increasing amounts of lithium carbonate (0, 500, 1000, and 2000 ppm), yielded homogeneous hybrid coatings with increased connectivity of nanometric silica cross-link nodes, covalently linked to the PMMA matrix, and improved adhesion to the aluminum substrate (AA7075). Electrochemical impedance spectroscopy (EIS), performed in 3.5% NaCl aqueous solution, showed that the improved structural properties of coatings with higher lithium loadings result in an increased corrosion resistance, with an impedance modulus up to 50 GΩ cm, and revealed that the lithium induced self-healing ability significantly improves their durability. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) suggest that the regeneration process occurs by means of lithium ions leaching from the adjacent coating toward the corrosion spot, which is restored by a protective layer of precipitated Li rich aluminum hydroxide species. An analogue mechanism has been proposed for artificially scratched coatings presenting an increase of the impedance modulus after salt spray test compared to the lithium free coating. These results evidence the active role of lithium ions in improving the passive barrier of the PMMA-silica coating and in providing through the self-restoring ability a significantly extended service life of AA7075 alloy exposed to saline environment.
在这项工作中，研究了锂离子在基于聚甲基丙烯酸甲酯（PMMA）-硅溶胶凝胶涂层的有机-无机涂层中引起的结构和活性腐蚀抑制效应。加入不同量的碳酸锂（0、500、1000 和 2000ppm），得到了均匀的杂化涂层，纳米级硅交联节点的连接性增加，与 PMMA 基质共价连接，并改善了对铝基底（AA7075）的附着力。在 3.5%NaCl 水溶液中进行的电化学阻抗谱（EIS）表明，具有更高锂负载的涂层的改进结构性能导致耐腐蚀性增加，阻抗模量高达 50GΩcm，并且表明锂诱导的自修复能力显著提高了它们的耐久性。飞行时间二次离子质谱（ToF-SIMS）和 X 射线光电子能谱（XPS）表明，再生过程是通过相邻涂层中的锂离子向腐蚀点渗出而发生的，这是由沉淀的富含锂的氢氧化铝物种形成的保护层来恢复的。提出了一种类似的机制，用于模拟经盐雾试验后具有划痕的涂层，与无锂涂层相比，其阻抗模量增加。这些结果证明了锂离子在改善 PMMA-硅涂层的被动屏障以及通过自修复能力提供显著延长暴露于盐环境的 AA7075 合金的使用寿命方面的积极作用。
