<p>This study investigated the effects of Co and Cu doping on the corrosion and passivation behaviors of the Ni₅₆Mn₂₅Ga_18.9Gd_0.1 shape-memory alloy in a 3.5 wt% NaCl solution. The results indicated that the corrosion resistance of the alloys initially improves and then decreases with increasing doping levels. The optimal corrosion resistance for both doping systems was achieved at a doping concentration of 2 at%. Beyond this concentration, further addition of doping elements weakened the corrosion resistance primarily due to the significant precipitation of the second phase, which can induce micro-galvanic coupling effects. Compared with the Cu-doped alloys, the Co-doped alloys generally exhibited superior corrosion resistance, which is likely attributable to the enrichment of Co(OH)₂ and Co₃O₄ compounds in the passive films of the Co-doped alloys, effectively isolating the corrosive medium from the alloy substrate and enhancing their corrosion resistance.</p> Graphical abstract <p></p>