为克服电化学技术在金属文物原位检测应用的难点，设计琼脂和硫酸钠作为凝胶电解质，以铂网和银/氯化银电极与模拟古代铸铁文物构建三电极体系，运用电化学阻抗技术对带锈铸铁试样的腐蚀进行检测，有效监控单宁酸作为缓蚀保护材料的作用时效性。结果表明：单宁酸会在样品表面生成缓蚀膜结构，将初期锈蚀铸铁的表面电荷转移电阻提升约10倍，对长期腐蚀铸铁的锈层电阻提升3倍，表面电荷转移电阻提升约2倍。但缓蚀膜层存在微裂隙，在后续加速腐蚀过程中会导致腐蚀介质的渗入，诱导新锈蚀生成并破坏膜结构，从而丧失保护效果。试验探索基于凝胶电解质的电化学阻抗原位检测技术和扫描电镜微观形貌的数据关联性，为开展金属文物保护科学监测提供支撑。

To overcome the difficulties in the practical application of electrochemical technology to the detection of metal cultural heritage, agar and sodium sulfate were used as gel electrolytes, and a three-electrode system was constructed with platinum mesh and silver/silver chloride electrodes and simulated ancient cast iron. Combined with electrochemical impedance technology, the corrosion detection of rusted cast iron could be realized, and the effect of tannic acid as a protective material could be effectively monitored. Experiments showed that tannic acid can form a corrosion-inhibiting film structure on the surface of the sample in a short period of time, which could increase the surface charge transfer resistance of thin-layered rusted cast iron by about 10 times. The rust resistance of thick-rusted iron could be increased by 3 times and the charge transfer resistance was increased by about 2 times. Besides, the inherent corrosion mechanism was not changed. However, there were micro-cracks in the corrosion-inhibiting film, which would lead to the infiltration of corrosive medium in the subsequent accelerated corrosion process, induce new corrosion and destroy the film structure, thus losing the protective effect. The experiment explored the data correlation between the electrochemical impedance in-situ detection technology based on gel electrolyte and the microscopic morphology of scanning electron microscope, which provides support for the scientific monitoring of metal cultural heritage protection.