Abstract: Eelectrochemical testing was carried out to 825 lined bimetal composite pipe using a three electrode system, and the polarization curves and electrochemical impedance spectra of three different interfaces between layers and four different interfaces between welds were obtained. The results show that the corrosion tendency of the X65 interface in the interlayer region was the highest, and the corrosion tendency of the three mixed interfaces in the weld seam region was the highest.