The electrochemical behavior of the Cu electrode in borax buffer solutions containing chloride ions and benzotriazole (BTA)-type inhibitors was studied by voltammetry and the photocurrent response method. A p-type photoresponse was observed from the Cu electrode in the pure borax buffer solutions. However, an n-type photoresponse was observed in chloride-containing borax buffer solutions if the Cl- concentration exceeded 0.08%. The transition from a p- to an n-type photoresponse is attributed to the doping of Cu2O film by the Cl- ions. Also, an n-type photoresponse was observed in solutions containing 0.10ppm BTA or above, with the magnitude of the anodic photocurrent increased with the concentration of BTA. The adsorbed BTA acted as a barrier which hindered O(2-)ions from entering into the underlying Cu2O film, thus forming some O2--deficient Cu2O regions of n-type conductivity. As a consequence, heterogeneous regions of p- and n-type conductivities were formed in the Cu2O film. The overall type of photoresponse depends on the proportion of p-type to n-type region, as well as on the applied electrode potential. It was observed that the greater the inhibition efficiency of the inhibitor, the larger the anodic photocurrent. Thus, the photoresponse method may be used to evaluate the inhibition efficiency of corrosion inhibitors.