<p>A new brightener was synthesized through the condensation of L-methionine and glutaraldehyde and evaluated for zinc electroplating on mild steel. Hull-cell experiments were conducted to optimize the bath composition and operating parameters. The corrosion performance of the resulting coatings was assessed using weight-loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution at 303 K. Incorporation of the brightener significantly enhanced the corrosion resistance of the zinc coatings, increasing the charge-transfer resistance from 133 to 855 Ω cm² and reducing the corrosion current density (I_corr) from 1.209 × 10⁻⁵ to 3.818 × 10⁻⁶ A cm⁻². Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed the formation of uniform, fine-grained bright deposits, while energy-dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared (FT-IR) spectroscopy confirmed the incorporation of the additive into the coating. Contact-angle measurements further indicated enhanced hydrophobicity of the bright zinc coating. These findings demonstrate that the condensation product of L-methionine and glutaraldehyde is an effective brightener for producing uniform, corrosion-resistant zinc coatings on mild steel.</p> Graphical abstract <p>Graphical representation of electrodeposition of Zn on mild steel substrate in presence of new brightener (MGC).</p>