搪瓷涂层的耐腐蚀及改良方法研究进展

Corrosion Resistance and Improvement Method of Enamel Coating

搪瓷具有良好的化学稳定性及结合性,且经济性好、制备工艺简单,有望成为优异的防腐涂层材料,已被尝试应用于石油化工、海洋工程、管道运输等领域的防腐工艺中,表现出了相对良好的防护效果。但它在强酸强碱环境下的耐腐蚀性不足且涂层中的气泡结构对耐腐蚀性有不利影响,同时高温烧结工艺也会影响金属基体的力学性能,这限制了防护性搪瓷涂层的应用。阐述了搪瓷作为防腐涂层的结构特点,在总结相关研究的基础上提出了目前搪瓷涂层的2种改良方法,即改进涂层成分和调控涂层结构。改进涂层成分可通过磨加法添加相关成分,调控搪瓷涂层组织结构,达到提高涂层[—Si—O—]网络及致密度的目的,进而提高涂层的耐腐蚀性;调控涂层结构主要包括制备多层涂层和热处理工艺,可在一定程度上降低涂层孔隙率、控制涂层晶体形核,这有助于提高涂层的有效厚度及可控制生成化学稳定相。在此基础上总结并提炼了这2种工艺的研究现状,讨论了上述2种技术方法对搪瓷涂层在酸、碱、盐腐蚀介质中的改良机理,并阐述了搪瓷涂层在不同服役介质中的耐腐蚀机制。同时,提出了目前技术的难点与可能的新方向,以期为搪瓷涂层的改良研究提供参考。

The corrosion problems in petrochemical,marine,pipeline,and other industries are becoming more severe,and the economic losses and corrosion prevention costs are increasing.A cost-effective and excellent corrosion-resistant coating material to promote the development of the petrochemical industry is of great importance.Enamel is an inorganic material with good chemical stability, bonding with metal, good economy and simple preparation process, which is expected to be an excellent material for anti-corrosion coating. The use of enamel as a protective coating has been tried in the above areas and has shown relatively excellent protection. However, there are still some shortcomings, such as insufficient corrosion resistance in strong acid and alkaline environments, and the negative effect of the pore structure in the coating on corrosion resistance, while the high-temperature sintering process also affects the mechanical properties of the metal substrate. In this work, the structural characteristics and corrosion resistance mechanisms of enamel as an anti-corrosion coating are discussed, and the improvement methods used in different corrosive media are summarized. Currently, there are two main types of methods used to improve the corrosion resistance of enamel coatings. The first method is to optimize the composition of the coating. SiO2 and ZrO2 mill additives can improve the coating [-Si-O-] network structure and coating density and their effect on improving the coating acid resistance is significant. The effect of ZrO2 mill additives to improve the coating alkali resistance is significant, but the mill additives of mineral components will increase the sintering temperature of enamel coatings, and the coefficient of thermal expansion and coating toughness have an effect. The second method is to improve the coating structure, including the preparation of multilayer coatings and the heat treatment process. Applying another layer on top of the single-layer enamel coating can seal the pores of the coating, which helps reduce the porosity and increase the effective thickness of the coating. An appropriate heat treatment process facilitates the removal of gases from the coating and controls the formation and growth of crystals in the coating, which can improve the corrosion resistance of the coating to some extent. However, both processes require multiple sintering, which has a negative effect on the mechanical properties of the metal substrate. Metal powder mill additives are expected to solve the shortcomings of current technology, which can react with the gas in the coating pores at high temperatures to reduce the porosity of the coating, and at the same time, the metal oxide formed can be reincorporated into the coating without other negative effects. Metal powder is also conducive to improving the toughness of the coating, which is expected to become a new idea of enamel coating improvement. In general, the enamel coatings show promising corrosion resistance properties and have significant economic and processing advantages over corrosion-resistant alloy materials. However, there are still some shortcomings to be solved, such as too high sintering temperature that may affect the mechanical properties of the metal substrate, and the lack of alkali resistance of the coating, etc. Therefore, further work is needed. These problems are expected to be solved by computer simulations and new testing techniques as advanced technologies are developed.