Abstract Organic-inorganic hybrid coatings have been prepared by a sol-gel route from 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) with triethylenetetramine (TETA) added in the sol formulation. The main goal of this research was to evaluate how the chemical structure of the GPTMS/TEOS/TETA hybrid coatings influences the corrosion of mild steel. The presence of TETA as an epoxy opening agent offers the possibility to form interconnected epoxy-amine and silica networks. It was found by means of 29Si HRMAS NMR spectroscopy that TETA acted as an efficient basic catalyst for the condensation of GPTMS and TEOS. This accelerates the gelation and gives limited shelf life to GPTMS/TEOS/TETA sols. Structural characterization of the cured hybrid coatings was performed using 13C and 29Si Solid State NMR spectroscopies. The results show that the epoxy amine reaction is the principal epoxide ring opening reaction. The slow formation of diol units with sols prepared with an excess of epoxy groups has also been observed. It was found that the polymerization of the organic network hindered the polymerization of the siloxane network. As a result, the film based on an epoxy rich off-stoichiometric formulation had a higher Persoz hardness value compared to the stoichiometric film. The corrosion behavior of the coatings in neutral chloride solution was studied through electrochemical impedance spectroscopy (EIS). The results revealed that barrier properties have been improved by the addition of TETA to sol-gel films. The films based on epoxy rich off-stoichiometric formulation and those base on stoichiometric formulation resulted in similar barrier properties but a higher resistance to interfacial delamination was observed for the epoxy rich off-stoichiometric films. The relationship between the film structure and its corrosion behavior was discussed.

中文翻译：

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具有相互连接的无机-有机网络的混合溶胶-凝胶涂层的耐腐蚀性与化学结构的关系

摘要 以 3-环氧丙氧基丙基三甲氧基硅烷 (GPTMS) 和四乙氧基硅烷 (TEOS) 为原料，在溶胶配方中加入三亚乙基四胺 (TETA)，通过溶胶-凝胶途径制备了有机-无机杂化涂料。本研究的主要目标是评估 GPTMS/TEOS/TETA 混合涂层的化学结构如何影响低碳钢的腐蚀。TETA 作为环氧开口剂的存在提供了形成互连的环氧-胺和二氧化硅网络的可能性。通过 29Si HRMAS NMR 光谱发现，TETA 是 GPTMS 和 TEOS 缩合的有效碱性催化剂。这加速了凝胶化并限制了 GPTMS/TEOS/TETA 溶胶的保质期。固化混合涂层的结构表征是使用 13C 和 29Si 固态 NMR 光谱进行的。结果表明，环氧胺反应是主要的环氧化物开环反应。还观察到用过量环氧基团制备的溶胶缓慢形成二醇单元。发现有机网络的聚合阻碍了硅氧烷网络的聚合。结果，与化学计量薄膜相比，基于富含环氧树脂的非化学计量配方的薄膜具有更高的 Persoz 硬度值。通过电化学阻抗谱（EIS）研究了涂层在中性氯化物溶液中的腐蚀行为。结果表明，通过向溶胶-凝胶薄膜中添加 TETA，阻隔性能得到了改善。基于富含环氧树脂的非化学计量配方的薄膜和基于化学计量配方的薄膜产生相似的阻隔性能，但观察到富含环氧树脂的非化学计量薄膜具有更高的界面分层抗性。讨论了薄膜结构与其腐蚀行为之间的关系。