To promote the engineering application of domestic Zr-3 plates in acetic acid-based plate heat exchangers, asystematic study was conducted to investigate the correlation between the microstructural evolution law, mechanicalproperties, and acetic acid corrosion behavior of tungsten inert gas (TIG) welded joints. Microstructure characterization ofthe welded joints was performed using optical microscopy (OM) and electron backscatter diffraction (EBSD) techniques,and the results reveal that the base metal (BM) is composed primarily of uniformly fine equiaxed α-Zr grains with anaverage grain size of 3.5 μm. In contrast, the weld zone (WZ) has a lath-like Widmanstätten structure of α-Zr, with a grainsize of 5.1 μm. Moreover, the kernel average misorientation (KAM) value of the weld joint is 0.37°, which is lower thanthat of the base metal (0.51°). Room-temperature tensile and microhardness tests demonstrate that the tensile strength ofZr-3 zirconium alloy TIG-welded joints decreases by 2.2% relative to that of the base metal, whereas the elongation significantly decreases by approximately 53.8%. Moreover, the microhardness of the welded joints is slightly greater thanthat of the base metal. The corrosion behavior of the welded joints in acetic acid solutions was studied via potentiodynamicpolarization curves and electrochemical impedance spectroscopy. The results demonstrate that across different acetic acidconcentrations, the corrosion current density of the WZ is slightly higher than that of the BM, indicating a marginallygreater corrosion tendency of the WZ; nevertheless, all the samples meet the industrial corrosion requirements for plate heatexchangers under acetic acid service conditions. This study confirms that TIG-welded Zr-3 plate joints exhibit excellentcomprehensive mechanical properties and acetic acid corrosion resistance.