The electrochemical behaviour of CuZn under conditions of illumination

Abstract

The influence of UV illumination on the passive behaviour of Cu37Zn in pH 9.2 and 13.0 chloride-containing electrolytes was studied using potentiodynamic polarisation tests, cyclic voltammetry and complex impedance spectroscopy. It was found that UV illumination exerted a slight activating effect on the passive behaviour in the alkaline pH 13.0 solution, with slightly higher passive current densities being recorded under conditions of illumination. A more pronounced UV illumination effect was observed in the pH 9.2 solution. This was characterised by a 4-fold increase in the passive current density, a shift in the breakdown potential by 250 mV in the active direction, a decrease in the charge transfer resistance and an increase in the double layer capacitance. These results are explained in terms of the nature of the passive film on CuZn, which consists of a complex layer involving ZnO · xH 2 O and Cu 2 O/CuO. On illumination, photo-decomposition of the n-type ZnO phase occurs leading to a modification of the passive layer rendering it more susceptible to pitting attack in the chloride environments.

Passivity and Corrosion of Cu–xZn (x = 10–40 wt%) Alloys in Borate Buffer Containing Chloride Ions

“…Localized corrosion resistance was significantly improved in the lower potential range, where zinc itself is active. Rudd and Breslin reported that UV illumination has an activating effect on the passivation of Cu-37Zn in chloride containing borate buffer [20]. Their results were explained in terms of the nature of complex films involving ZnOAExH 2 O and Cu 2 O/CuO oxides.…”

“…Passivation in slightly alkaline solution, with and without addition of chloride, has not received much attention [15][16][17][18][19][20]. The passivation behaviour of brasses under these conditions is interesting since the passivation of the copper and zinc components occurs at a pH value of 9 [21].…”

“…The passivation behaviour of brasses under these conditions is interesting since the passivation of the copper and zinc components occurs at a pH value of 9 [21]. It has been recognized that the passivation of brasses is based on the formation of a complex oxide layer consisting of ZnO and Cu 2 O and CuO [16][17][18][19][20][21]. Morales et al studied extensively a-, (a +b)-and b-brasses with Zn contents of 28 wt.%, 39 wt.% and 48 wt.%, respectively [17][18][19].…”

“…The passivation of Cu is established as being due to formation of a duplex Cu 2 O/CuO layer [24][25][26], whereas a ZnO/Zn(OH) 2 layer is responsible for passivation of Zn [27][28][29]. Various commercial brasses have been described, for example 61Cu-35Zn-3.25Pb [15], 58Cu-40Zn-1.8Pb and 58Cu-38Zn-3.5Pb [30], Cu37Zn brass [20,22], and a-, (a +b)-and b-brasses [17][18][19]. In our previous work the passivation behaviour of a series of Cu-xZn alloys (x = 10, 20, 30 and 40 wt.%) and Cu and Zn metals was studied in borate buffer, pH = 9.2, by a combination of electrochemical measurements and X-ray photoelectron spectroscopy (XPS) [16].…”

Electrochemical studies on the corrosion of brass in seawater under anaerobic conditions

“…Brass is an alloy (Cu-Zn) commonly used for decoration purposes and also in heating exchanging systems, e.g., desalination and power generation plants [1,2]. The corrosion behavior of brass has been extensively studied in a wide range of experimental conditions, with specific interest in the dezincification [3][4][5], passivation, and pitting corrosion [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”