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Fig. 1. Copper anode polarisation curves run in cpy+0.5 M sul- phuric acid (0 <cpy <15 mM) at v=0.005 V s~!. (a) Full curves. (b) Magnified plot of the region of the polarisation curves where inflections are observed. Anode apparent area = 0.2 cm?. Tempera- ture: 298 K. The electrochemical instrumentation consisted of a PAR model 362 scanning potentiostat coupled to a Houston Omnigraphic recorder. The polarisation curves were recorded at a scan rate of 0.005 V s~! to

Figure 1 Copper anode polarisation curves run in cpy+0.5 M sul- phuric acid (0 <cpy <15 mM) at v=0.005 V s~!. (a) Full curves. (b) Magnified plot of the region of the polarisation curves where inflections are observed. Anode apparent area = 0.2 cm?. Tempera- ture: 298 K. The electrochemical instrumentation consisted of a PAR model 362 scanning potentiostat coupled to a Houston Omnigraphic recorder. The polarisation curves were recorded at a scan rate of 0.005 V s~! to

Related Figures (8)

Fig. 2. Tafel plots for the electrodissolution of a copper electrode in 0.5 M sulphuric acid and in 15 mM TU+0.5 M sulphuric acid. Anode apparent area = 0.2 cm?. v=0.005 V s~'. Temperature: 298 K
Fig. 2. Tafel plots for the electrodissolution of a copper electrode in 0.5 M sulphuric acid and in 15 mM TU+0.5 M sulphuric acid. Anode apparent area = 0.2 cm?. v=0.005 V s~'. Temperature: 298 K
Fig. 4. Cyclic voltammograms of copper anodes in: (a) 0.5 M sulphuric acid (blank); (b) 0.5 mM TU+0.5 M sulphuric acid. v=0.05 V s~'. Temperature: 298 K. Fig. 3. (a) Dependence of the breakdown potential (£,) on TU concentration. Copper anode in cy, +0.5 M sulphuric acid (0< Cry < 15 mM). (b) Dependence of the anodic current density read at E=0.08 V on c;y. Temperature: 298 K.
Fig. 4. Cyclic voltammograms of copper anodes in: (a) 0.5 M sulphuric acid (blank); (b) 0.5 mM TU+0.5 M sulphuric acid. v=0.05 V s~'. Temperature: 298 K. Fig. 3. (a) Dependence of the breakdown potential (£,) on TU concentration. Copper anode in cy, +0.5 M sulphuric acid (0< Cry < 15 mM). (b) Dependence of the anodic current density read at E=0.08 V on c;y. Temperature: 298 K.
Fig. 5. (a) Single-cycle voltammograms run between 0.0 V and — 0.3 V including a holding time at 0.0 V. (b) Plot of the Q,/Q, ratio vs. the uppet potential limit (Z,) obtained from the first cycle between E, and —0.3 V. (c) Single cycle voltammograms run between 0.1 V and —0.3 V including a holding time at 0.1 V. 0.5 mM FDS +0.5 M sulphuric acid. v= 0.05 V s~!. Temperature: 298 K. eee eS eee eee Oe ee ee eee To determine the influence of FDS, as compared to TU, on the electrodissolution of copper, voltam- mograms of copper in 0.5 M sulphuric acid + 0.5 mM FDS were run, covering the potential range — 0.30 < E <0.075 V, i.e. where FDS is formed from TU electro- oxidation (Fig. 4). In these runs the potential routine included a potential holding at EF, in the range — 0.100< F,<0.075 V for the time ct (Fig. 5a). The voltammetric scan from 0.025 V downward shows the appearance of peak II,, which is related to the electrore- duction of Cu(J) soluble species, the height of this peak increasing with t. Voltammograms also show that the positive to negative voltammetric charge ratio (Q,/Q,) depends on the upper potential limit, E, (Fig. 5b). These results indicate that the presence of FDS alone assists the formation of Cu(I) soluble species at these potentials. As £, is moved from — 0.10 to 0.075 V, the relative contribution of Cu(I) electrodissolution to the overall anodic process appears to be increased. Besides Q,/Q,, decreases almost linearly with E,, approaching 1 As shown by polarisation curves at 0 V, even at the lowest cry there is a considerable hindrance of the anodic reactions. Therefore, it was interesting to inves- tigate the lowest potential at which the coverage of the copper surface by TU could be detected. For this purpose, voltammograms of thallium upd covering the potential range where the alloyi were run ing effect is negligible [32—35]. The blank voltammograms (Fig. 6) show the anodic and cathodic peaks of thal jum upd in the potential range — 0.65 to — 0.45 V. The anodic to cathodic charge ratio is Q,/OQ,=1, and involves a charge density of 0.35 mC cm~? a reported [34]. he process as has been
Fig. 5. (a) Single-cycle voltammograms run between 0.0 V and — 0.3 V including a holding time at 0.0 V. (b) Plot of the Q,/Q, ratio vs. the uppet potential limit (Z,) obtained from the first cycle between E, and —0.3 V. (c) Single cycle voltammograms run between 0.1 V and —0.3 V including a holding time at 0.1 V. 0.5 mM FDS +0.5 M sulphuric acid. v= 0.05 V s~!. Temperature: 298 K. eee eS eee eee Oe ee ee eee To determine the influence of FDS, as compared to TU, on the electrodissolution of copper, voltam- mograms of copper in 0.5 M sulphuric acid + 0.5 mM FDS were run, covering the potential range — 0.30 < E <0.075 V, i.e. where FDS is formed from TU electro- oxidation (Fig. 4). In these runs the potential routine included a potential holding at EF, in the range — 0.100< F,<0.075 V for the time ct (Fig. 5a). The voltammetric scan from 0.025 V downward shows the appearance of peak II,, which is related to the electrore- duction of Cu(J) soluble species, the height of this peak increasing with t. Voltammograms also show that the positive to negative voltammetric charge ratio (Q,/Q,) depends on the upper potential limit, E, (Fig. 5b). These results indicate that the presence of FDS alone assists the formation of Cu(I) soluble species at these potentials. As £, is moved from — 0.10 to 0.075 V, the relative contribution of Cu(I) electrodissolution to the overall anodic process appears to be increased. Besides Q,/Q,, decreases almost linearly with E,, approaching 1 As shown by polarisation curves at 0 V, even at the lowest cry there is a considerable hindrance of the anodic reactions. Therefore, it was interesting to inves- tigate the lowest potential at which the coverage of the copper surface by TU could be detected. For this purpose, voltammograms of thallium upd covering the potential range where the alloyi were run ing effect is negligible [32—35]. The blank voltammograms (Fig. 6) show the anodic and cathodic peaks of thal jum upd in the potential range — 0.65 to — 0.45 V. The anodic to cathodic charge ratio is Q,/OQ,=1, and involves a charge density of 0.35 mC cm~? a reported [34]. he process as has been
Fig. 6. Voltammograms of copper in 0.1 mM thallium sulphate + 0.5 M sulphuric acid; before (full trace) and after (dotted trace) immer- sion in 0.01 mM TU+0.5 M sulphuric acid for 30 s under open circuit conditions. Electrode area 0.2 cm?. v=0.05 V s~!. Tempera- ture: 298 K.
Fig. 6. Voltammograms of copper in 0.1 mM thallium sulphate + 0.5 M sulphuric acid; before (full trace) and after (dotted trace) immer- sion in 0.01 mM TU+0.5 M sulphuric acid for 30 s under open circuit conditions. Electrode area 0.2 cm?. v=0.05 V s~!. Tempera- ture: 298 K.
Fig. 7. Sequential absorption spectra of the electrolyte solution after different anodisation times (charge). Copper anode in 0.5 mM TU + 0.5 M sulphuric acid. The peak at 790 nm corresponds to the absorption of Cu(II) hexa-aquo ions.
Fig. 7. Sequential absorption spectra of the electrolyte solution after different anodisation times (charge). Copper anode in 0.5 mM TU + 0.5 M sulphuric acid. The peak at 790 nm corresponds to the absorption of Cu(II) hexa-aquo ions.
Fig. 8. Wide XPS spectrum of the anodic film formed on copper in 0.5 mM TU +0.5 M sulphuric acid at E=0.06 V for t= 7200 s. : Wide XPS spectra of film I, average thickness chy x 160 nm, showed peaks corresponding to Cu, S, O and C, and Auger peaks of Cu and O (Fig. 8). Narrow high
Fig. 8. Wide XPS spectrum of the anodic film formed on copper in 0.5 mM TU +0.5 M sulphuric acid at E=0.06 V for t= 7200 s. : Wide XPS spectra of film I, average thickness chy x 160 nm, showed peaks corresponding to Cu, S, O and C, and Auger peaks of Cu and O (Fig. 8). Narrow high
Fig. 9. EDAX spectrum of the anodic film formed on copper in 0.5 mM TU+0.5 M sulphuric acid at 0.1 V for 8100 s.
Fig. 9. EDAX spectrum of the anodic film formed on copper in 0.5 mM TU+0.5 M sulphuric acid at 0.1 V for 8100 s.
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Analytical ChemistryElectroanalytical ChemistryUV/Vis spectroscopyAnodic Copper DissolutionCorrosion Inhibitor
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