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In the HCN-H₂S-H₂O corrosion environment, the protective performance of the FeS film can be comprehensively evaluated through various multidimensional approaches: microstructural and morphological characterization, which involves using scanning electron microscopy to examine the density of the film layer, the uniformity of its thickness, as well as any defects such as gaps and grooves; combined with energy spectrum analysis to determine the elemental composition of the film layer, thereby assessing whether there are issues such as porosity or insufficient bonding to the substrate. Electrochemical performance testing: Electrochemical impedance spectroscopy is used to measure the charge transfer resistance of the film layer; the higher the resistance value, the stronger the film layer’s ability to prevent corrosion agents from penetrating it ； At the same time, the corrosion current density is measured through polarization curve tests; the lower the current density, the better the protective effect of the FeS film. Medium stability test: The samples with FeS films were immersed in an H₂S aqueous solution containing CN⁻ to observe whether the film layer was complexed and dissolved. The integrity of the film layer and the corrosion rate of the substrate before and after immersion were measured in order to assess its resistance to damage caused by CN⁻. Mechanical and erosion resistance tests: Fluid erosion tests are conducted to examine the breakdown and delamination of the FeS film at different flow rates, in order to determine whether it can continue to prevent corrosive agents from penetrating under flowing conditions, thus avoiding electrochemical acceleration of corrosion that may occur as a result of film damage.