Electrochemical studies with a Cu–5wt. % Ni alloy in 0.5 M H₂SO₄

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• 作者：Hurtado ; M.R.F. ; Sumodjo ; P.T.A. ; Benedetti ; A.V.
• 关键词：Copper&ndash ; nickel alloys ; Impedance spectroscopy ; Sulfuric acid ; Polarization measurements
• 刊名：Electrochimica Acta
• 出版年：2003
• 出版时间：August 15, 2003
• 年：2003
• 卷：48
• 期：1
• 页码：2791-2798
• 全文大小：338 K

文摘

The electrochemical behavior of the annealed Cu–5wt. % Ni alloy in 0.5 M H₂SO₄ was studied by means of open-circuit potential (E_OCP) measurements, cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and quasi-stationary linear potential sweep. The hydrodynamics of the system was also studied. This material is constituted by a single α₁ phase. The anodic behavior of a Cu–Ni alloy in H₂SO₄ consists fundamentally on the electrodissolution of Cu, its main component, and the formation of a sulfur-containing passive layer. The presence of Ni decreases the rate of Cu oxidation, mostly at high positive potentials. The impedance spectra, obtained for the unrotating electrode, can be interpreted in terms of a simple charge-transfer reaction across a surface layer. When the electrode is rotated, the occurrence of an inductive loop evidenced the existence of an adsorbed layer. All the resistance estimated from the proposed equivalent circuits diminished with the electrode rotation rate, emphasizing the influence of ion transport in the overall electrode process. The system presented two anodic Tafel slopes: 40 mV dec⁻¹ for E<255 mV and 67 mV dec⁻¹ for E>275 mV. A Tafel slope of 40 mV dec⁻¹ evidences that copper dissolution can be interpreted in terms of the mechanism proposed by Mattsson and Bockris. The second Tafel suggests that at potentials more positive than 275 mV, copper dissolves according to a mechanism that considers the disproportionation of adsorbed Cu(I) species.