Anodic oxidation of lead in aqueous carbonate solutions. II. Film formation and dissolution in the pH range 9 to 14

Abstract

The anodic oxidation of lead has been studied in aqueous carbonate solutions at pH values in the range 9 5 pH 5 14. The solid films formed on the electrode surface have been identified by X-ray diffractometry. ' The dissolution and film formation processes have been studied by a number of electrochemical techniques at rotating disk electrodes. The anodic oxidation process can be divided into two distinct regions. In the main anodic oxidation process, a variety of surface phases is formed. The nature of the phase formed is pH-dependent. Plumbonacrite (Pb100(OH)6(C03)6) formation is observed at all pH values and predominates at pH 2 13. At pH < 11, cerussite (PbCO,) is the predominant phase, whereas at intermediate pH values, hydrocerussite (Pb3(0H)2(C03)2) predominates. The dissolution rate of pb2+ species from the electrode surface is directly proportional to the solubility of the predominant phase present. At more positive potentials, a reactivation, involving increased dissolution and a further stage of film formation, is observed. Litharge (PbO) is observed to grow underneath the initially formed basic lead carbonates. Dissolution occurs either by the field-assisted dissolution of the base-layer on the electrode or by metal dissolution through faults in the base-layer. Chem. 66,2941Chem. 66, (1988.Operant dans des solutions aqueuses de carbonate et 5 des pH allant de 9 a 14, on aetudiC I'oxydation anodique du plomb. On a utilist la diffraction des rayons-X pour identifier les films solides qui se forment i la surface de l'electrode. Faisant appel a un certain nombre de techniques Clectrochimiques impliquant des electrodes 5 disque tournant, on a Ctudie les processus de formation et de dissolution du film. On peut diviser les processus d'oxydation anodique en deux regions distinctes. Dans le processus principal d'oxydation anodique, il se forme une grande variCtC de phases ~u~erficielles. La nature de la phase qui se forme depend du pH. On observe la formation de la plumbonacrite (Pb100(OH)6(C03)6) a tous les pH; cette formation predomine a un pH 2-13. A un pH 5 11, la cCrusite (PbCO,) est la phase predominate alors qu'a des pH intermediaires, l'hydrocerusite (Pb3(OH)2(C03)2) pridomine. La taux de dissolution des espkces pb2+ 5 partir de la surface de I'Clectrode est directement proportionnel 2 la solubilite de la phase predominate qui est presente. A des potentiels plus positifs, on observe une reactivation impliquant une dissolution accrue ainsi qu'un autre stage de formation de film. On a observe que du litharge (PbO) se forme sous la couche de carbonates basiques de plomb qui se forment au depart. La dissolution se produit soit par une dissolution, aidCe par le champ, de la couche de base de l'electrode soit par une dissolution du metal i travers les defauts de la couche de base.[Traduit par la revue] IntroductionLead carbonates occur (or are expected) as corrosion products on artifacts as diverse as wine-bottle tops (I), bullets used in the American Civil War (2), water pipes (3, 4), and nuclear waste co...

Evaluating Battery‐like Reactions to Harvest Energy from Salinity Differences using Ammonium Bicarbonate Salt Solutions

“…As shown in the current profile obtained by cyclic voltammetry (CV) in 1 m AmB (Figure b), less current was delivered during the cathodic sweep, meaning that the PbCO 3 was only partially reduced to Pb. This irreversibility is an intrinsic property of Pb in a carbonate solution; on the cathodic sweep, the base layer is reduced first and a more negative potential is required to further reduce the deposited layer . Therefore, the accumulation of PbCO 3 layer was inevitable because the potential range was quite narrow during the energy harvesting cycles, which would gradually increase the resistance and require more voltage for the reactions (Figure S3).…”

EXAFS studies of the chemical state of lead and copper in corrosion products formed on the brass surface in potable water

“…The literature data indicate that three main types of lead carbonates (cerussite PbCO3, hydrocerussite, plumbonacrite Pb~0(COa)6(OH)60) are predominant solids formed at corroding surfaces in the presence of dissolved carbonates Schock, 1989;Taylor and Lopata, 1984;Colling, 1987;Shoesmith, 1988]. Of those, plumbonacrite is observed only in a narrow range of conditions at pH>13, while hydrocerussite or a mixture of hydrocerussite and cerussite are commonly found.…”

“…Lead in potable water constitutes a significant threat to exposed populations. To predict its release, the nature of lead compou0ds formed because of the corrosion of lead-tin solder and leaded brasses must be known Schock, 1980;Shoesmith, 1988]. In the latter case, lead compounds are ot~en amorphous and mixed with dissimilar species of other metals.…”