A STUDY OF THE COPPER ELECTRODE BEHAVIOR IN BORAX BUFFER SOLUTIONS CONTAINING CHLORIDE-IONS AND BENZOTRIAZOLE-TYPE INHIBITORS BY VOLTAMMETRY AND THE PHOTOCURRENT RESPONSE METHOD

The electrochemical behavior of the Cu electrode in borax buffer solut ions containing chloride ions and benzotriazole (BTA)-type inhibitors was studied by voltammetry and the photocurrent response method. A p-t ype photoresponse was observed from the Cu electrode in the pure borax buffer solutions. However, an n-type photoresponse was observed in ch loride-containing borax buffer solutions if the Cl- concentration exce eded 0.08%. The transition from a p- to an n-type photoresponse is att ributed to the doping of Cu2O film by the Cl- ions. Also, an n-type ph otoresponse was observed in solutions containing 0.10ppm BTA or above, with the magnitude of the anodic photocurrent increased with the conc entration of BTA. The adsorbed BTA acted as a barrier which hindered O (2-)ions from entering into the underlying Cu2O film, thus forming som e 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 propor tion of p-type to n-type region, as well as on the applied electrode p otential. It was observed that the greater the inhibition efficiency o f the inhibitor, the larger the anodic photocurrent. Thus, the photore sponse method may be used to evaluate the inhibition efficiency of cor rosion inhibitors.