Aluminum alloys AA5083 - H111 (Al-Mg) and AA6061-T6 (Al-Mg-Si) are extensively utilized in marine and structural applications owing to their excellent corrosion resistance and high tensile strength. However, joining these dissimilar alloys poses challenges in maintaining mechanical integrity and corrosion resistance. In this study, Tungsten Inert Gas (TIG) welding was employed to fabricate dissimilar joints between AA5083-H111 and AA6061-T6 using conventional ER5356 and scandium-modified filler rods (ER5356 + 0.25 wt.% Sc and ER5356 + 0.5 wt.% Sc). The welding parameters-voltage (20 - 26 V), current (160 - 220 A), and gas flow rate (14 - 26 L/min) were optimized using the Taguchi method and ADAM gene algorithm. The optimized process parameters for the 0.5 wt.% Sc filler (24.6 V, 195.8 A, 24.8 L/min) resulted in superior tensile strength (282.6 MPa), higher microhardness (90HV), and improved ductility (16% elongation). Microstructural analysis revealed a refined grain structure in the weld zone with scandium addition. Corrosion and wear analyses confirmed the lowest mass loss (0.18 g) and coefficient of friction (0.22) for the 0.5 wt.% Sc-modified welds, indicating enhanced good resistance to erosion corrosion. Overall, the inclusion of scandium in ER5356 filler rods significantly improved the corrosion resistance and good mechanical performance of dissimilar TIG-welded AA5083-H111 and AA6061-T6 joints, making it an effective approach for marine and aerospace applications.