<p>This study investigates the corrosion behavior of AZ91 magnesium alloy reinforced with Al₂O₃ nanoparticles at varying weight percentage of 1%, 1.5% and 2%. Corrosion tests were conducted in a 3.5% NaCl solution using a Gamry potentiostat through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. Corrosion parameters, including current density (I_corr) and corrosion potential (E_corr), were determined using the Tafel extrapolation method, while charge transfer resistance, polarization resistance, and constant phase element values were extracted from fitting based on equivalent circuit models. Nyquist plots revealed that the unreinforced AZ91 alloy exhibited a larger capacitive loop diameter compared to the nanocomposite samples, indicating higher corrosion resistance. Tafel analysis further supported this, with increasing I_corr values and sharper cathodic slopes observed in nanocomposites, reflecting faster cathodic reactions. Surface analysis through scanning electron microscopy (SEM) showed the presence of corrosion-induced cracks on all samples. Energy-dispersive X-ray analysis (EDAX) confirmed the formation of MgCl₂ as a corrosion product, which may act as a passive layer, reducing further electrolyte ingress into the matrix through existing surface cracks.</p>