In regions with a concentration of heavy industries, the surfaces of external insulation equipment such as transmission line insulators and substation insulators often accumulate significant amounts of metal contaminants, posing a serious threat to the performance and safe operation of these devices. This study focuses on XP-160 porcelain insulators, each string consisting of 3 insulators, and investigates their AC characteristics under different pollution levels and different proportions of metallic iron powder. By analyzing the leakage current test results, the impact of contaminant components on the AC flashover characteristics of insulator strings is evaluated. The experimental results indicate that the soluble substance NaCl has a greater impact on the flashover voltage than the insoluble metallic iron powder. As the content of metallic iron powder increases, the flashover voltage of the tested samples gradually rises, but the impact of the metal ratio on the flashover voltage is not significant under low contamination levels. Both the level of contamination and the proportion of metal affect the leakage current, and the higher NaCl content leads to lower conductivity of the contaminated layer and a greater leakage current. The findings of this study provide important reference value for ensuring the operational safety and reliability of the power system.