Etude de la dissolution du bromure cuivreux formé sur le cuivre

Abstract

1 12 (1984).La dissolution du bromure cuivreux, form6 par oxydation Clectrochimique du cuivre immergC en solution aqueuse de NaBr, a CtC CtudiCe. La concentration en NaBr a Ct C variCe de 0,l M a 1,2 M alors que le pH Ctait de 4. Le produit de corrosion accumulC sur 1'Clectrode est constituC de cristaux de CuBr y. La prtsence de ce composC contribue a I'enrichissement local de la solution en cuivre dissous pr6s de I'Clectrode. Cet enrichissement se traduit par une tension d7Clectrode en circuit ouvert bien caractkristique. Elle est Cgale a environ -149 mV (ECS) sur une Clectrode en position stationnaire immergte dans une solution 0,2 M NaBr. La dissolution complete du CuBr coincide, pour sa part, a une chute rapide de la tension. Cette chute de tension a permis de dCfinir le temps de transition T a partir duquel la vitesse de dissolution du CuBr a Ct C calculte. Par exemple, la vitesse de dissolution est de 0,074 f 0,003 mA cm-' en courant tquivalent pour une Clectrode en position stationnaire en prCsence d'une solution 0,2 M NaBr non agitCe. Elle est aussi constante jusqu'i la disparition complkte du composC. Par ailleurs, I'utilisation de I'Clectrode a disque tournant a mis en evidence que la dissolution est entierement dominee par la diffusion des ions en phase liquide. Les rCsultats experimentaux sont compatibles avec la presence simultanCe du CuBr, et du ~u~r tcomme especes diffusantes. Enfin, les courbes de polarisation potentiodynamiques montrent deux vagues d'oxydation. Une portion non nkgligeable du courant de dissolution, sinon la quasi-totalitt, se traduit par la formation de CuBr sur I'tlectrode qui est le seul produit de corrosion prCsent.ROBERT-LOUIS BROSSARD. Can. J . Chem. 62, 1 1 12 (1984).' The dissolution of cuprous bromide, formed by the electrochemical oxidation of copper immersed in aqueous NaBr, has been studied. NaBr concentration was varied between 0. I and 1.2 M at pH 4. The corrosion product accumulating on the electrode is crystalline y-CuBr. The presence of this material contributes to the local enrichment of dissolved copper close to the electrode. This enrichment leads to a characteristic electrode voltage in open circuit, which is about -149 mV (ECS) at a stationary electrode immersed in a solution of 0.2 M NaBr. The complete dissolution of CuBr coincides with a rapid fall in voltage which permits the definition of the transition time T from which the speed of CuBr dissolution has been calculated. For example, the speed of dissolution is 0.074 2 0.003 mA cm-' in a current equivalent for a stationary electrode in the presence of a non-stirred solution of 0.2 M NaBr. This is constant until the complete disappearance of the CuBr. On the other hand, use of a rotating disc electrode demonstrates that the dissolution is entirely dominated by the diffusion of ions in the liquid phase. The experimental results are compatible with the simultaneous presence of CuBr, and CUB^:-as diffusing species.Finally, the potentiodynamic polarization curves show two oxidation waves. A non-negligible por...

Copper dissolution in bromide medium in the absence and presence of hexamethylenetetramine (HMTA)

“…3 indicate that the copper anodic dissolution products (in 0.1 M bromide medium and pH = 3 in the absence of HMTA) formed in A1 and A2 are reduced in C1 and C2, respectively. This results contradicts a previous work [12] which claims that the species formed in both A1 and A2 are reduced together in the cathodic region C1. However, cathodic potentials studied in Ref.…”

“…In the cathodic region, the peak C1 was observed at À190 mV for E r = À 100 mV. At this E r value, the formation of the soluble species (CuBr 2 À ) is expected [12,27]. The cathodic peak C1 shifted to more negative potential values as the E r became more positive (Fig.…”

“…The cathodic peak C1 is related to the reduction of these surface species. The cathodic peak C2 was not reported before [12].…”

“…1). The CuBr formation is still the predominant process in the A2 region [12]. The cathodic peak C1 is related to the reduction of these surface species.…”

“…However, the formation of Cu(II) have been reported for copper dissolution in chloride medium [16,17] at relatively lower overpotentials than for copper dissolution in bromide [12].…”