The corrosion behavior of aluminum and aluminum silicon alloys in 0.1 M NaOH solution in the absence and presence of gelatin was studied using potentiostat polarization, electrochemical impedance spectroscopy (EIS), cyclic voltammetry and potentiodynamic anodic polarization techniques. The percentage inhibition efficiency increases with increasing the concentration of gelatin and with decreasing temperature as well as Si content. This was attributed to a lower affinity of the inhibitor to adsorb on Si than on Al. The inhibitory action of gelatin was explained in terms of adsorption of gelatin on the surface of Al or Al–Si alloys forming a barrier of mass and charge transfer leading to protect the metal surface from the aggressive ones. The adsorption of gelatin on the metal surface follows Freundlich isotherm. Some activated thermodynamic parameters were calculated and discussed