C. Lazarides

The mechanism of the formation of positive battery plates from pure lead 1. cyclic voltammetry

Abstract The electrochemical behaviour of a pure lead electrode in sulphuric acid—perchloric acid electrolyte mixtures has been examined by cyclic voltammetry In the lead/lead sulphate region, the perchlorate ion promotes surface attack on the lead by displacing the passivating sulphate ion. The effect increa The mechanism in the lead sulphate/lead dioxide region possibly involves a reduction in the thickness of the passivating layer by the perchlorate anion

The perchlorate-assisted formation of lead dioxide on lead

Perchloric acid affects the phase formation process during the oxidation of lead to PbO2 in dilute sulphuric acid. In sulphuric acid, the reaction involves a two-dimensional instantaneous nucleation process for the production of PbO2. In the mixed acid, the growth of PbO2 in low concentrations (20 mM) of added perchlorate ion remains two-dimensional but the nucleation becomes progressive and at higher perchlorate concentrations phase formation occurs by three-dimensional growth. A range of perchlorate concentration (30–40 mM) exists where the attack is on an ‘advancing front’ (analogous to the electrodeposition of a metal from solution), in which the PbO2 steadily advances into the metal. A mechanism is proposed for the Planté reaction process.

The formation of PbSO4 at the PbO2 planté electrode

Abstract The development of PbSO4 in porous PbO2 electrodes formed by the Plante process was investigated by the impedance method. The results were significantly different from those reported earlier for thin films of PbO2 formed on lead by potentiostatting in the PbO2 region. The data allow for deductions to be made regarding the effect of the porous structure.

The electrochemistry of partially discharged Plant electrodes

The electrochemistry of partially discharged Planté electrodes has been investigated. The reduction of partially discharged electrodes continues in the manner expected for a crystallization and growth limited electrode process. The oxidation of partially discharged Planté electrodes is less well defined and it appears that the effects due to nucleation of lead sulphate are removed by the initial discharge from the fully charged condition.

The planté formation process for lead—acid positive electrodes

Abstract The perchlorate assisted oxidation of lead to lead dioxide in dilute sulphuric acid containing perchlorate ion has been investigated under conditions similar to those used for Plante electrode production. The optimum concentration of perchlorate ion has been estimated. It is shown that if the electrode is not fully passivated by lead sulphate before the potential is increased to form PbO 2 , the process of PbO 2 formation proceeds progressively.

The Planté (PbO2) electrode

Abstract PbO 2 electroformed from lead with the aid of perchlorate ion as the forming agent constitutes the Plante electrode. The impedances of such electrodes in 3.58 M H 2 SO 4 were measured. The impedance loci were interpreted in terms of charge transfer at porous electrodes. The presence of a film of PbSO 4 at the electrode surface distorts the Warburg impedance line at low frequencies. The conversion of PbO 2 to PbSO 4 affects the electrode characteristics and the attendant changes were interpreted. The presence of an inductive component in the electrode analogue is due to the oxygen redox reaction.

On the cycling of positive planté electrodes

Abstract The development, in cell cycling tests, of PbSO 4 crystals in Plante electrodes has been investigated by S.E.M. Electrodes were examined electrometrically at various states-of-charge in the uncycled condition. They were then electrometrically and microscopically examined after 80 cycles of 10% rated capacity at the 10 h rate (in, respectively, the 90, 75, 50 and 25% nominal charged condition). A final examination was carried out after a constant voltage float recharge at 2.25 V per cell (140 h). The crucial point in determining the amount of capacity available from the float-recharged cell is the size of PbSO 4 crystallites. This is influenced by the extent of the mean state-of-charge of the electrodes.

The impedance of a planté PbO2 electrode polarized in H2SO4 solution

Abstract We report briefly the results of rapid impedance measurements on Plante-formed PbO 2 electrodes polarized negatively in H 2 SO 4 solution. Useful information is only obtained within 50 mV of the reversible potential. At other potentials the development of PbSO 4 complicates the results sufficiently to render the information uninterpretable.

The anodic oxidation of lead in H2SO4-based solutions to form soluble species

Abstract The dissolution of lead at an anode to form freely soluble species has been examined by the rotating-disc technique. The kinetics of the process are discussed in terms of an adspecies mechanism.

Synergism in corrosion inhibition

Abstract The synergism observed with two commercial corrosion inhibitors has been investigated using the faradaic impedance technique. The data show that the efficiency of single inhibiting compounds can be significantly lower than that of simple mixtures, and that the ratios employed are critical.