Comment on “Distribution of Nickel Hydroxide in Sintered Nickel Plaques Measured by Radiotracer Method during Electroimpregnation” [J. Electrochem. Soc., 133, 17]

Abstract

Term Atmospheric Oxidation of High Purity Iron," Frankenthal et al. report that (i) pure iron in a stoppered bottle maintained a bright finish over a long period (years), (it) there have been no reports of the passivation of iron in the atmosphere for periods longer than several weeks, (iii) the oxide film thickness, with a correction for contamination, after twenty years was no more than 5-6 nm, and (iv) there is a similarity between passivation in air and film growth in solution (anodic oxidation).We should like to comment on these points. Vernon, working in this laboratory in the 1920's, 2 showed that no significant corrosion of iron or steel took place in ordinary air in the absence of solid particles on the metal surface. He demonstrated this by exposing specimens within muslin cages for periods of up to 314 days in a laboratory atmosphere. Such specimens, free /Tom solid pollutants, not only remained bright over this period but also showed greatly reduced susceptibility to corrosion when subsequently exposed outside the muslin cage. (A specimen held in a muslin cage for 900 days and later mounted behind glass has remained bright and rust free over the last 50 years in this laboratory.)In the 1950's, Kubaschewski and Brasher, also in this laboratory, ~ investigated the uptake of ~'Cr from chromate solutions on abraded mild steel pre-exposed to air for periods of up to one year. They showed that the thickening of the air-formed film led to a reduction in chromium uptake. From an analysis of the kinetics, they calculated the thickness of the air-formed film and showed that the thicknesses reported by Gulbransen 4 and Winterbottom ~ were similar in magnitude and fitted the same kinetic expression, allowing for some uncertainty in roughness factor (r.f.). After correction for r.f., this work gave a film thickness of 2.5 nm after 1 year's growth in air, and the value extrapolated to 20 years would be 2.8 rim. The specimens examined by Kruger ~ and by Sato and Cohen 7 were probably very smooth, and the method now reported by Frankenthal presumably is relatively insensitive to surface roughness. Given the uncertainties involved, the agreement between all these figures is reasonably close.Brasher et al. 8 later determined rate constants for passivating film growth in inhibitive solutions of nitrite,

Electrochemical Precipitation of Nickel Hydroxide

“…SFt vvg = 1-e w~ .... [10] Wg,max .... is the maximum loading capacity, which can be estimated from the density of Ni(OH)2, pj Wg .... = pj [11] However, the experimental results indicate that the actual maximum loadLag level is lower than the density of Ni(OH)2, 4.15 g/cm 3, due to the filling of the porous electrode and the plugging of the pores. Figure 8 compares the experimental data with the theoretical loading curves predicted by Eq.…”

“…preparing nickel hydroxide electrodes presently being used in nickel-cadmium, nickel-zinc, and nickel-hydrogen batteries (1)(2)(3). Despite the fact that there are several advantages of this method over the conventional chemical impregnation method (4)(5)(6)(7)(8)(9)(10), the conditions of the process have been experimentally determined so far through trial and error procedures. There is a need to apply the principles of electrochemical engineering in order to establish the conditions which would lead to a process competitive from both economics and quality considerations.…”

Electrochemical Impregnation of Nickel Hydroxide: Flow‐Through vs. Stagnant Electrodes

“…It is suggested that by a careful selection of the flow rate, flow direction, and electrode configuration, optimum conditions for the fabrication of nickel hydroxide electrodes can be achieved. Manuscript submitted Feb. 6,1989; revised manuscript received June 20, 1989.…”

“…onstrated that at low and high frequency, the diffusional impedance at a sinusoidal electrode shows the same proportionality to frequency as the planar electrode, but for intermediate values the functional behavior is more complex; in this range, the magnitude is not proportional to ~-1/2 and the phase lag is frequency dependent. To develop these calculations, we utilize a perturbation solution to the transient-diffusion equation for the concentration field, originally presented to calculate the Cottrell-like current on the sinusoidal surface (6), with the perturbation parameter being the ratio of the amplitude-to-period length, A. The accuracy and limitation of the perturbation solution for the diffusional impedance is determined and the error is shown to be less than 2% for moderate wall oscillation amplitude (A < 0.15).…”

“…Studies on cathodic electrochemical impregnation have been stimulated by the trend to reduce loading level, since electrodes fabricated by electrochemical impregnation exhibit improved utilization with reduced loading. Nevertheless, with cathodic electrochemical impregnation, it is well known that thickening of plaques usually occurs (1,(4)(5)(6). This is especially true at high impregnation current densities.…”