Corrosion Mechanism Suggested Based on Electrochemical Analysis and SVET for Uncoated Tinplate and Post Coated With a Hybrid Film

The tinplate, used in the packaging sector and formed from a metal substrate, comprises a steel base which has undergone a surface treatment to produce a thin layer of FeSn2, a tin layer and an oxide tin layer. Currently, packaging using surface treatment is based on the use of chromates because these metals provide an excellent corrosion resistance. Nontoxic alternatives to pre-treatments have been developed in recent years to replace the chromate process. The aim of this work is to analyze the performance of a new hybrid organic-inorganic film obtained from sol-gel consisting of the alkoxide precursors 3-(Trimethoxysilylpropyl)methacrylate (TMSM) and tetraethoxysilane (TEOS) with the addition of cerium nitrate with the scanning vibrating electrode technique (SVET), and electrochemical and morphological characterizations. Moreover, the evolution of the corrosion of the substrate was evaluated to propose a mechanism of corrosion. The results showed a galvanic coupling between the Sn/SnO2 coat (cathode) and the defects exposed at the ferrous base (anode). The organic-inorganic hybrid film containing a cathodic corrosion inhibitor was able to retard the corrosion of the tinplate.

本研究涉及的马口铁（tinplate）以金属基体为基材制备而成，广泛应用于包装领域，其钢基底经表面处理后形成二锡化铁(FeSn₂)薄层、锡层及氧化锡层。当前，包装领域所用的表面处理工艺多以铬酸盐为核心体系，因其可赋予基材优异的耐腐蚀性能。近年来，科研人员已开发出可替代铬酸盐工艺的无毒前处理方案。本研究旨在分析一种新型溶胶-凝胶法制备的有机-无机杂化薄膜的性能：该薄膜以3-三甲氧基硅丙基甲基丙烯酸酯(3-(Trimethoxysilylpropyl)methacrylate, TMSM)与正硅酸乙酯(tetraethoxysilane, TEOS)两种醇盐为前驱体，并添加硝酸铈，采用扫描振动电极技术(scanning vibrating electrode technique, SVET)、电化学表征及形貌表征手段开展测试。此外，本研究还对基体的腐蚀演化过程进行了评估，以此推导其腐蚀机理。结果表明，锡/二氧化锡涂层（阴极）与暴露的铁基体缺陷（阳极）之间存在电偶耦合效应。添加阴极缓蚀剂的有机-无机杂化薄膜可有效延缓马口铁的腐蚀进程。