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A simple method for monitoring the inhibition of copper corrosion based on photopotential measurements
Journal of Electroanalytical Chemistry, 361(1993)
265-267
265
JEC 02853
Short communication
A simple method for monitoring the inhibition of copper corrosion based on photopotential measurements Xiao-Yan
Liu and Guo-Ding
Zhou
Electrochemical Research Group, Shanghai Institute of Electric Power, Shanghai 200090 (China)
Mai-Zhi
Yang and Sheng-Min
Cai
Department of Chemistry, Peking University, Beijing 100871 (China)
B.H. Loo Department of Chemistry, Uniuersity of Alabama in Huntsville, Huntscille, AL 35899 (USA), and Department of Chemistry, National University of Singapore, Kent Ridge S.0511 (Singapore) (Received
22 September
1992; in revised
form 23 March
1993)
1. Introduction Benzotriazole (BTA) is one of the most effective corrosion inhibitors for copper and its alloys, and has been used as such for years [l]. Numerous investigations on the inhibition action of BTA on Cu have been performed with different analytical techniques (see references cited in ref. 2). In particular, several studies on the photoresponses of Cu corrosion and its inhibition have been made using the photoelectrochemical technique [3-131. Based on these earlier results, we have devised a simple method for monitoring the inhibition action of BTA on the corrosion of Cu within several hours of its immersion in chloride solutions. The conclusion derived from this method agrees favorably with that from the a.c. impedance spectroscopic measurements. 2. Experimental Copper plates of 0.25 cm2 area embedded in epoxy resin were polished with different grades of emery papers and then cleaned with distilled water. Photopotential measurements were carried out in an electrochemical cell with a flat quartz window. The electrolytes were 3% NaCl solutions (pH 6) containing several different concentrations of BTA. The light source was a 150 W tungsten-halogen lamp, and was 0022-0728/93/$6.00
chopped at a frequency of 41.5 Hz. A lock-in amplifier was used to measure the open-circuit potential of the Cu electrode with respect to a saturated calomel electrode (SCE). The a.c. impedance spectroscopic experiments were described earlier [14]. 3. Results and discussion Figure 1 shows the open-circuit photopotential I/p,, vs. the immersion time for the Cu electrode in 3% NaCl solutions containing 0, 0.05, 0.5 and 1.0 ppm of BTA. It was observed that I/p,, rapidly increased to + ‘I.08 mV in the first 2 h of immersion in chloride solutions containing no BTA. After that it decreased steadily and stayed at -0.91 mV after a 24 h immersion. The values of T, were 7, 4.5 and 8.7 h when the BTA concentrations were 0, 0.05 and 0.5 ppm respectively, where T, is the immersion time at which the photopotential curve crosses the abscissa, i.e. I/p,, = 0. In NaCl solution containing 1.0 ppm BTA, a small but steady positive value of I/ph was observed, a behavior very different from that observed at lower BTA concentrations. To understand these observations better, a.c. impedance spectroscopic experiments were carried out under similar conditions. Figure 2 shows the corresponding Nyquist plots from the a.c. impedance spectroscopic measurements. The polarization resistance R, is estimated [15] to be 5.8, 3.8, 7.2, and 17 kR cm2 0 1993 - Elsevier Sequoia S.A. All rights reserved
266
X.-Y Liu et al. / Monitoring the inhibition
of coppercorrosion
and 1.0 ppm of BTA. With the BTA concentrations of 0, 0.05 and 0.5 ppm, E,,,, moved negatively at the early stage of immersion. It was especially pronounced for the first two cases which indicated that their corrosion rates were higher. The initial step of corrosion was the formation of a film consiting of a p-type Cu,O [3,12], reaction (1). Therefore, VP,, rapidly increased in a positive direction at the early stage of immersion as the thickness of the Cu,O film increased. When sufficient Cu2+ ions were produced in the solution because of the Cu corrosion, reactions (2a) and (2b) ensued which resulted in the formation of a Cu,O film with an n-type photoresponse [ 121.
-1.2 0
4
8
12
16
20
24
2Cu+20H-
Immersion Time/h Fig. 1. Photopotential Vn,, vs. immersion time for Cu electrodes in 3% NaCl solutions containing (a) 0, (b) 0.05, (d) 0.5, and (d) 1.0 ppm BTA.
for 3% NaCl solutions containing 0, 0.05, 0.5 and 1.0 ppm of BTA respectively. Table 1 summarizes the values of T,, R,, and Vend for different concentrations of BTA, where I&, is VP,, at the end of a 24 h immersion ( Vph was found somewhat constant after this period). From the R, values in Table 1, it was found that the inhibition action of BTA on the Cu corrosion occurred when the BTA concentration was 0.5 ppm or greater. In addition, a linear correlation existed between the values of Tt and R,, that is, the larger R, is the larger Tt. Therefore, Tt values may be used in lieu of R, to characterize the corrosion process of copper especially in cases where a diffusion process is occurring or the R, value is difficult to obtain by the a.c. impedance spectroscopic technique because of a limitation in the accessibility in the low frequency range. Figure 3 shows the variation of the corrosion potential E,,,, with the immersion time for the Cu electrodes in 3% NaCl solutions containing 0, 0.05, 0.5,
-
Cu,O + H,O + 2e-
Cu2++ e- 2Cu++ 20H-
(1)
cu+ -
(2a) Cu,O + H,O
(2b) The n-type cuprous chloride Cu,Cl, also appeared on the electrode surface as the corrosion continued because of its partial transformation from Cu,O [3,13]. It is believed therefore that both p and n regions coexist on the electrode surface, and their relative amounts determine the value of VP,,. As p-Cu,O was predominant at the early stage of immersion, I$, was positive. With an increasing time of immersion, the relative amount of n region was increased, and hence I/p,, became negative. When the electrode was partially covered with BTA, a smaller amount of n region was formed because the bare area of the electrode was smaller than that in the absence of BTA. Therefore, with increasing BTA concentration in the range O-O.5 ppm, l/end became.less and less negative, as shown in Table 1. When the BTA concentration reached 1.0 ppm, the growth rate of p-Cu,O film was retarded and the formation of the n region was inhibited. Therefore, I(,,, rose slowly and remained positive at 0.13 mV.
6
0
0 3
6 -10e3Z’/
9 0
12
cm2
Fig. 2. Nyquist plots for Cu electrodes in 3% NaCl solutions ing (a) 0, (b) 0.05, (c) 0.5, and (d) 1.0 ppm BTA.
contain-
I 4
I
I 8
I
Immersion
I 12
I
I 16
I
11 20
II 24
Time/h
Fig. 3. Variation of corrosion potential E,,, with immersion time for Cu electrodes in 3% NaCl solutions containing (a) 0, (b) 0.05, (c) 0.5, and (d) 1.0 ppm BTA.
X.-Y. Liu et al. / Monitoring the inhibition of copper corrosion TABLE tions
1. The Tr, R, and Vend values
lBTAl/ppm
T,/h
R, /kR
0 0.01 0.05 0.10 0.50 1 .oo
7.0 3.6 4.5 5.0 8.7 _
5.8 3.0 3.8 4.5 7.2 17.0
at different
cm*
BTA concentra-
Vend imV
-0.91 - 0.58 -0.41 - 0.37 -0.29 + 0.13
Similar photoresponse behavior was observed at higher concentrations (Fig. 4). With a further increase in the BTA concentration from 1.0 to 15.0 ppm, I/pi, became smaller and smaller. The l/end values were 0.13, 0.058, 0.023, and 0.017 mV for BTA concentrations of 1.0, 5.0, 10.0 and 15.0 ppm respectively, and they never became negative. The observed decrease in Vph with an increase in the BTA concentration may be due to the following reasons. First, as discussed earlier, the growth of pCu,O film was inhibited by an increase in the BTA concentration and hence a decrease in the thickness of the oxide film. Second, there was a stronger absorption of the irradiation by the surface BTA film as the film
0.16
$
0.12
h d ‘Z 0.08 B 0
3 ‘;
0.04
2
0 0
4
8
12
16
20
24
Immersion Time/h Fig. 4. Photopotential VP,, vs. immersion time for Cu electrodes in 3% NaCl solutions containing (a) 1.0, (b) 5.0, (c) 10.0, and (d) 15.0 ppm BTA.
267
grew in thickness with an increase in the BTA concentration, which consequently reduced the photoresponse I/p,, of the underlying oxide film. In conclusion, we have demonstrated that the photopotential measurements provide a simple method for monitoring the inhibition action of BTA on the corrosion of Cu within several hours of its immersion in chloride solutions. This technique may be used to study and screen potential inhibitors on Cu corrosion, and it may be used to investigate the corrosion of other systems which have similar photoresponses to the Cu electrode. Acknowledgment The support of this work by the National Natural Science Foundation of China is gratefully acknowledged. References 1 Proctor and Gamble Ltd., Br. Patent 652, 229, 1947. 2 G. Zhou, S. Cai, L. Song, H. Yang, A. Fujishima, A. Ibrahim, Y.G. Lee and B.H. Loo, Appl. Surf. Sci., 52 (1991) 227 and references cited therein. 3 G. Trabanelli, F. Zucchi, G. Brunoro and G.P. Bolognesi, Thin Solid Films, 13 (1972) 131. 4 W. Paatsch, Ber. Bunsenges. Phys. Chem., 81 (1977) 645. 5 U. Sander, H.-H. Strehblow and J.K. Dohrmann, J. Phys. Chem., 85 (1981) 447. 6 B. Pointu, M. Braizaz, P. Poucet, J. Rosseau and N. Muhlstein, J. Electroanal. Chem., 122 (1981) 111. 7 B. Pointu, M. Braizaz, P. Poucet and J. Rosseau, J. Electroanal. Chem., 151 (1983) 65. 8 F. Di Quarto, S. Piazza and C. Sunseri, Electrochim. Acta, 30 (1985) 315. 9 U. Collisi and H.-H. Strehblow, J. Electroanal. Chem., 210 (1986) 213. 10 A. Aruchamy, G. Zhou and A. Fujishima, J. Electroanal. Chem., 244 (1988) 3. 11 A. Aruchamy and A. Fujishima, J. Electroanal. Chem., 266 (1989) 397. 12 W. Siripala and K.P. Kumara, Semicond. Sci. Technol., 4 (1989) 465. 13 C. Pan, M. Yang, G. Zhou and S. Cai, Acta Phys. Chim. Sin., 9
265-267
265
JEC 02853
Short communication
A simple method for monitoring the inhibition of copper corrosion based on photopotential measurements Xiao-Yan
Liu and Guo-Ding
Zhou
Electrochemical Research Group, Shanghai Institute of Electric Power, Shanghai 200090 (China)
Mai-Zhi
Yang and Sheng-Min
Cai
Department of Chemistry, Peking University, Beijing 100871 (China)
B.H. Loo Department of Chemistry, Uniuersity of Alabama in Huntsville, Huntscille, AL 35899 (USA), and Department of Chemistry, National University of Singapore, Kent Ridge S.0511 (Singapore) (Received
22 September
1992; in revised
form 23 March
1993)
1. Introduction Benzotriazole (BTA) is one of the most effective corrosion inhibitors for copper and its alloys, and has been used as such for years [l]. Numerous investigations on the inhibition action of BTA on Cu have been performed with different analytical techniques (see references cited in ref. 2). In particular, several studies on the photoresponses of Cu corrosion and its inhibition have been made using the photoelectrochemical technique [3-131. Based on these earlier results, we have devised a simple method for monitoring the inhibition action of BTA on the corrosion of Cu within several hours of its immersion in chloride solutions. The conclusion derived from this method agrees favorably with that from the a.c. impedance spectroscopic measurements. 2. Experimental Copper plates of 0.25 cm2 area embedded in epoxy resin were polished with different grades of emery papers and then cleaned with distilled water. Photopotential measurements were carried out in an electrochemical cell with a flat quartz window. The electrolytes were 3% NaCl solutions (pH 6) containing several different concentrations of BTA. The light source was a 150 W tungsten-halogen lamp, and was 0022-0728/93/$6.00
chopped at a frequency of 41.5 Hz. A lock-in amplifier was used to measure the open-circuit potential of the Cu electrode with respect to a saturated calomel electrode (SCE). The a.c. impedance spectroscopic experiments were described earlier [14]. 3. Results and discussion Figure 1 shows the open-circuit photopotential I/p,, vs. the immersion time for the Cu electrode in 3% NaCl solutions containing 0, 0.05, 0.5 and 1.0 ppm of BTA. It was observed that I/p,, rapidly increased to + ‘I.08 mV in the first 2 h of immersion in chloride solutions containing no BTA. After that it decreased steadily and stayed at -0.91 mV after a 24 h immersion. The values of T, were 7, 4.5 and 8.7 h when the BTA concentrations were 0, 0.05 and 0.5 ppm respectively, where T, is the immersion time at which the photopotential curve crosses the abscissa, i.e. I/p,, = 0. In NaCl solution containing 1.0 ppm BTA, a small but steady positive value of I/ph was observed, a behavior very different from that observed at lower BTA concentrations. To understand these observations better, a.c. impedance spectroscopic experiments were carried out under similar conditions. Figure 2 shows the corresponding Nyquist plots from the a.c. impedance spectroscopic measurements. The polarization resistance R, is estimated [15] to be 5.8, 3.8, 7.2, and 17 kR cm2 0 1993 - Elsevier Sequoia S.A. All rights reserved
266
X.-Y Liu et al. / Monitoring the inhibition
of coppercorrosion
and 1.0 ppm of BTA. With the BTA concentrations of 0, 0.05 and 0.5 ppm, E,,,, moved negatively at the early stage of immersion. It was especially pronounced for the first two cases which indicated that their corrosion rates were higher. The initial step of corrosion was the formation of a film consiting of a p-type Cu,O [3,12], reaction (1). Therefore, VP,, rapidly increased in a positive direction at the early stage of immersion as the thickness of the Cu,O film increased. When sufficient Cu2+ ions were produced in the solution because of the Cu corrosion, reactions (2a) and (2b) ensued which resulted in the formation of a Cu,O film with an n-type photoresponse [ 121.
-1.2 0
4
8
12
16
20
24
2Cu+20H-
Immersion Time/h Fig. 1. Photopotential Vn,, vs. immersion time for Cu electrodes in 3% NaCl solutions containing (a) 0, (b) 0.05, (d) 0.5, and (d) 1.0 ppm BTA.
for 3% NaCl solutions containing 0, 0.05, 0.5 and 1.0 ppm of BTA respectively. Table 1 summarizes the values of T,, R,, and Vend for different concentrations of BTA, where I&, is VP,, at the end of a 24 h immersion ( Vph was found somewhat constant after this period). From the R, values in Table 1, it was found that the inhibition action of BTA on the Cu corrosion occurred when the BTA concentration was 0.5 ppm or greater. In addition, a linear correlation existed between the values of Tt and R,, that is, the larger R, is the larger Tt. Therefore, Tt values may be used in lieu of R, to characterize the corrosion process of copper especially in cases where a diffusion process is occurring or the R, value is difficult to obtain by the a.c. impedance spectroscopic technique because of a limitation in the accessibility in the low frequency range. Figure 3 shows the variation of the corrosion potential E,,,, with the immersion time for the Cu electrodes in 3% NaCl solutions containing 0, 0.05, 0.5,
-
Cu,O + H,O + 2e-
Cu2++ e- 2Cu++ 20H-
(1)
cu+ -
(2a) Cu,O + H,O
(2b) The n-type cuprous chloride Cu,Cl, also appeared on the electrode surface as the corrosion continued because of its partial transformation from Cu,O [3,13]. It is believed therefore that both p and n regions coexist on the electrode surface, and their relative amounts determine the value of VP,,. As p-Cu,O was predominant at the early stage of immersion, I$, was positive. With an increasing time of immersion, the relative amount of n region was increased, and hence I/p,, became negative. When the electrode was partially covered with BTA, a smaller amount of n region was formed because the bare area of the electrode was smaller than that in the absence of BTA. Therefore, with increasing BTA concentration in the range O-O.5 ppm, l/end became.less and less negative, as shown in Table 1. When the BTA concentration reached 1.0 ppm, the growth rate of p-Cu,O film was retarded and the formation of the n region was inhibited. Therefore, I(,,, rose slowly and remained positive at 0.13 mV.
6
0
0 3
6 -10e3Z’/
9 0
12
cm2
Fig. 2. Nyquist plots for Cu electrodes in 3% NaCl solutions ing (a) 0, (b) 0.05, (c) 0.5, and (d) 1.0 ppm BTA.
contain-
I 4
I
I 8
I
Immersion
I 12
I
I 16
I
11 20
II 24
Time/h
Fig. 3. Variation of corrosion potential E,,, with immersion time for Cu electrodes in 3% NaCl solutions containing (a) 0, (b) 0.05, (c) 0.5, and (d) 1.0 ppm BTA.
X.-Y. Liu et al. / Monitoring the inhibition of copper corrosion TABLE tions
1. The Tr, R, and Vend values
lBTAl/ppm
T,/h
R, /kR
0 0.01 0.05 0.10 0.50 1 .oo
7.0 3.6 4.5 5.0 8.7 _
5.8 3.0 3.8 4.5 7.2 17.0
at different
cm*
BTA concentra-
Vend imV
-0.91 - 0.58 -0.41 - 0.37 -0.29 + 0.13
Similar photoresponse behavior was observed at higher concentrations (Fig. 4). With a further increase in the BTA concentration from 1.0 to 15.0 ppm, I/pi, became smaller and smaller. The l/end values were 0.13, 0.058, 0.023, and 0.017 mV for BTA concentrations of 1.0, 5.0, 10.0 and 15.0 ppm respectively, and they never became negative. The observed decrease in Vph with an increase in the BTA concentration may be due to the following reasons. First, as discussed earlier, the growth of pCu,O film was inhibited by an increase in the BTA concentration and hence a decrease in the thickness of the oxide film. Second, there was a stronger absorption of the irradiation by the surface BTA film as the film
0.16
$
0.12
h d ‘Z 0.08 B 0
3 ‘;
0.04
2
0 0
4
8
12
16
20
24
Immersion Time/h Fig. 4. Photopotential VP,, vs. immersion time for Cu electrodes in 3% NaCl solutions containing (a) 1.0, (b) 5.0, (c) 10.0, and (d) 15.0 ppm BTA.
267
grew in thickness with an increase in the BTA concentration, which consequently reduced the photoresponse I/p,, of the underlying oxide film. In conclusion, we have demonstrated that the photopotential measurements provide a simple method for monitoring the inhibition action of BTA on the corrosion of Cu within several hours of its immersion in chloride solutions. This technique may be used to study and screen potential inhibitors on Cu corrosion, and it may be used to investigate the corrosion of other systems which have similar photoresponses to the Cu electrode. Acknowledgment The support of this work by the National Natural Science Foundation of China is gratefully acknowledged. References 1 Proctor and Gamble Ltd., Br. Patent 652, 229, 1947. 2 G. Zhou, S. Cai, L. Song, H. Yang, A. Fujishima, A. Ibrahim, Y.G. Lee and B.H. Loo, Appl. Surf. Sci., 52 (1991) 227 and references cited therein. 3 G. Trabanelli, F. Zucchi, G. Brunoro and G.P. Bolognesi, Thin Solid Films, 13 (1972) 131. 4 W. Paatsch, Ber. Bunsenges. Phys. Chem., 81 (1977) 645. 5 U. Sander, H.-H. Strehblow and J.K. Dohrmann, J. Phys. Chem., 85 (1981) 447. 6 B. Pointu, M. Braizaz, P. Poucet, J. Rosseau and N. Muhlstein, J. Electroanal. Chem., 122 (1981) 111. 7 B. Pointu, M. Braizaz, P. Poucet and J. Rosseau, J. Electroanal. Chem., 151 (1983) 65. 8 F. Di Quarto, S. Piazza and C. Sunseri, Electrochim. Acta, 30 (1985) 315. 9 U. Collisi and H.-H. Strehblow, J. Electroanal. Chem., 210 (1986) 213. 10 A. Aruchamy, G. Zhou and A. Fujishima, J. Electroanal. Chem., 244 (1988) 3. 11 A. Aruchamy and A. Fujishima, J. Electroanal. Chem., 266 (1989) 397. 12 W. Siripala and K.P. Kumara, Semicond. Sci. Technol., 4 (1989) 465. 13 C. Pan, M. Yang, G. Zhou and S. Cai, Acta Phys. Chim. Sin., 9