The aim of this work was to investigate the efficiency of 1-phenyl-4-methylimidazole for corrosion inhibition of copper in 3% NaCl solution. The formation of a thick layer on the copper surface was observed in the presence of this compound. The protective properties of this layer were characterized by means of cyclic voltammetry and through AFM and SEM/EDX measurements. Voltammetric measurements were performed in stirred and quiescent solutions as well as at different immersion times. Voltammetric measurements showed that the protective properties of the layer were enhanced by stirring and with an increase in immersion time. The time dependence of the protective layer formation was characterized by AFM measurements. From SEM/EDX measurements it was concluded that this protective layer has a complex structure consisting of the inhibitor and corrosion products.