Effects of 1,4-naphthoquinone (NQ) have been investigated as a corrosion inhibitor for aluminum in aerated and de-aerated solutions of 0.50 M NaCl using potentiodynarnic polarization, chronoamperometry (CA), open-circuit potential (OCP), electrochemical impedance spectroscopic (EIS), scanning electron microscopic (SEM), cyclic voltammetric, and quartz crystal analyzer (QCA) techniques. These measurements revealed that the presence of NQ shifted the corrosion and pitting potentials to more noble values and decreased the anodic currents in the passive region in both aerated and de-aerated chloride solutions, and the surface and polarization resistances are increased as the concentration of NQ is increased. The most effective concentration of NQ for corrosion inhibition was found to be 1.0x10(-3) M in both aerated and de-aerated chloride solutions. The QCA data indicate that adsorption of NQ molecules plays an important role in protecting the pits on the aluminum surface. The SEM images show that the presence of NQ decreased the severity of the pitting corrosion of aluminum to a great extent at -675 mV versus Ag/AgCl. (C) 2005 Elsevier Ltd. All rights reserved.