INFLUENCE OF CHLORIDE IONS UPON SEMICONDUCTOR PROPERTIES OF OXIDE FILMS ON COPPER AND BRASS

The photocurrent-potential relationship for copper and brass electrodes under periodic illumination was obtained during slow (6 mV center dot s(-1))) cyclic potential scans with lock-in amplifier in 0.1 molo center dot L-1) Na2B4O7 contianing variable concentration of NaCl. Only cathodic photocurrent was exhibited on photocurrent vs. potential curves in absence of or in the presence of low concentrations of chloride ion in the solution. The minimum concentration of NaCl at which an anodic photocurrent peak appeared is 7.5x10(-4)) g center dot g(-1)) for copper and 3.8x10(-3)) g center dot g(-1)) for brass. With the continuous increase of NaCl concentraton the peak area of anodic photocurrent increases and that of cathodic decreases. The appearance of anodic photocurrent peak and its magnitude on photocurrent vs. potential curve may be served as a criterion for the characterization of the corrosion extent of copper material by Cl-1.