FLiNaK熔盐氧化还原电位对316不锈钢腐蚀行为的影响及机理研究

Molten fluoride salts are promising used in nuclear reactors, hydrogen-production facilities, solar thermal power generation and other fields. However, the compatibility (corrosion) of service metal materials in molten fluoride salts is one of the key problems and must be solved in the practical application. .The corrosion of structural materials is closely related to the oxidation and reduction (redox) potential of molten fluoride salt. The main attention of this project is paid to investigate the effects of the redox potential on the corrosion behavior of 316 stainless steel (316SS) in molten fluoride salt and clarify the related corrosion mechanism by means of corrosion thermodynamic analysis, in-situ electrochemical measurement, immersion test etc. The major works are included as follows: erecting a variety of potential-acidity diagrams from simple to complex systems such as single metal (Fe, Cr, Ni), complex binary alloy (Fe-Cr, Ni-Cr, Fe-Ni), ternary alloy (Fe-Cr-Ni) and 316SS in molten FLiNaK salt, exploring the change of the thermodynamic corrosion behavior such as the immunity, corrosion and passivity areas of 316SS and its main components in molten FLiNaK salt with redox potential, investigating the corrosion behaviors of 316SS such as the electrochemical dynamics curves, corrosion morphologies, corrosion depth, corrosion products and microstructure in molten FLiNaK with different redox potential, and revealing experimentally the effect of redox potential on the corrosion behaviors of 316SS. Finally, the mechanism of the effect of the redox potential on the corrosion behavior of 316SS in molten FLiNaK salt is clarified by the theoretical and experimental results. The present work has important meaningful for the solution of the compatibility of metal materials with molten fluoride salt.

氟化物熔盐（氟盐）在核反应堆、高温制氢、太阳能热发电等领域具有广阔的应用前景，但服役金属材料与氟盐的相容性（腐蚀）问题是其实际应用中必须解决的关键问题之一。.氟盐的腐蚀性与其氧化还原（Redox）电位密切相关，本项目结合热力学分析、原位电化学测量、浸泡试验等方法，研究Redox电位对316不锈钢氟盐腐蚀影响规律及机理，构建Fe、Cr、Ni纯金属，Fe-Cr等二元合金，Fe-Cr-Ni三元合金和316不锈钢等从简单到复杂体系在FLiNaK熔盐中电位-酸度图，揭示316不锈钢腐蚀热力学行为随Redox电位变化规律，研究316不锈钢在不同Redox电位的FLiNaK熔盐中电化学腐蚀行为和腐蚀形貌、腐蚀深度、腐蚀产物及微观结构等变化，实验上揭示316不锈钢腐蚀随Redox电位变化规律，综合理论和实验结果澄清Redox电位影响316不锈钢腐蚀的机理。研究结果对解决金属材料的氟盐腐蚀问题具有重要意义。

氟化物熔盐（氟盐）在核反应堆、高温制氢、太阳能热发电等领域具有广阔的应用前景。316不锈钢是商用成熟材料，具有价格低廉，使用经验丰富等诸多优点是氟盐应用环境中重要候选材料。但316不锈钢在氟化物熔盐中耐蚀性差，解决316不锈钢的氟盐腐蚀问题是其实际应用中必须解决的关键问题之一。本项目计算了Cr、Fe、Ni在FLiNaK熔盐中的电位-酸度（E-pO2-）关系，为解释316不锈钢氟盐腐蚀行为和选择熔盐电位调控介质提供理论依据。获得了316不锈钢在含有EuF3/EuF2缓冲对的FLiNaK熔盐中电化学腐蚀动力学规律，包括：EuF3/EuF2对316不锈钢开路电位、极化曲线、电化学阻抗谱等影响规律，揭示了EuF3/EuF2调控316不锈钢氟盐腐蚀机理。获得了316不锈钢在含有Cr和CrF2的FLiNaK熔盐中腐蚀和电化学腐蚀行为规律，包括Cr价态变化对316不锈钢自腐蚀电位、自腐蚀电流密度、极化曲线特征、腐蚀失重、腐蚀形貌、腐蚀深度、元素分布等影响规律，揭示了不同价态Cr对316不锈钢氟盐腐蚀影响机理。研究了异质材料对316不锈钢在高温氟盐中质量迁移腐蚀影响机理，探索了通过调控熔盐化学组成抑制316不锈钢质量迁移腐蚀方法。研究结果为深入认识氟盐氧化还原电位调控对结构材料腐蚀行为影响提供了理论和试验依据。为促进316不锈钢等成熟度高、价格低廉、耐蚀性相对较差的结构材料在氟盐体系的实际应用提供技术储备。