In-situ photoelectrochemical microscopic method (PEM) has been used to characterize the spatial variation of the film formed on the copper surface in buffer-borax solutions (pH 9.2) with different concentration of benzotriazole (BTA) and combined benzotriazole methanoic acid ester (CBTME). It is shown from PEM that the transition of photocurrent on copper electrode from p-type to n-type at the action of the certain amount of the inhibitors. the more concentrated the inhibitors, the more the n-type photoresponse and the more effective the inhibition. The inhibition action is not only related to the properties of inhibitors but also to the applied potential. At a certain potential the coexistance of the p-type and n- type zones at the different position on the copper electrode and the process of the transition of the photocurrent from p-type to n-type can be observed.

Key words: CORROSION INHIBITORS, BENZOTRIAZOLE, BENZOTRIAZOLE P, METHYL ESTER