Thermogalvanic Potentials and Currents at Aluminum Surfaces in Industrial Water

Abstract

normal until it began to fluctuate at @. Although this fluctuation was found on two of the four cells in this cycle, it is not characteristic of a normal charge. Lacking any other information, this erratic behavior might be confused with a bad electrical connection or breakdown of measuring component. A similar fluctuation ~ppears at Q on cell 2, but, from the additional data taken, it is obvious that the fluctuations in the cell voltage are due to fluctuations in the negative plate potential @, and are also reflected in the H concentration at Q. The volmne of the gas meter per revolution was large enough to obscure a similar fluctuation appearing in the gassing rate at @, but it was undoubtedly there.Gas measurements @ also indicate that gas evolution began early in the charge for cell 2. This suggests that the cell was either not deeply discharged or that it was not taking a charge. Calculations from the gas record @ indicate that the net charge put into the positive plate of cell 2 was, however, about equal to the rated capacity of the cell. This would be the maximum, since positive plate capacity normally limits the cell capacity. In sharp contrast, the negative plate appears to have charged quite efficiently with only a limited amount of H having been evolved during the charge | When the charge was stopped, over twice the rated capacity of the cell appears to have been put into the negative plate; yet the lack of H evolution showed it was far from being fully charged. Furthermore, the negative plate potential began to drop near the end of the following discharge @ in spite of the long charge. All this suggests that the self-discharge rate of the Cd plate was high under these conditions of stand and that there was a high ratio of negative plate to positive plate capacity in this battery.More recent work on similar cells indicates that the apparent amount of charge taken by the Cd plate was not necessarily related to the true capacity. Gas measurements during stand show that the gassieg rate of the Ni-Cd battery dropped off rapidly during the first few hours of stand. This lack of gas evolution does not mean that selfdischarge had stopped, however, for residual discharges following stands indicate appreciably more capacity loss than could be accounted for by the evolved gas. While the cell characteristics were being observed on a 24 hr/day basis, the cell actually began to absorb oxygen from the atmosphere; this oxygen in turn oxidized the Cd plate. Thus, it is sometimes possible to pick up and interpret unexpected characteristics from the detailed measurements on a 24 hr/day basis. A permanent record is also available for future evaluation in the light of later developments.ABSTRACT Potentials and galvanic currents at 2S A1 surfaces in Columbia River water were studied between room temperature and 100~ The A1 potential changed by approximately 0.6 v over this interval, becoming more anodic with increase in temperature. Similar but somewhat smaller changes in potential were noted in buffer solutions.]~y coupli...

Thermogalvanic corrosion of Alloy 31 in different heavy brine LiBr solutions

“…the formation of a passive film on the anode surface), so it is not suitable. Thus, in practice, any enhanced corrosion as a consequence of the apparition of a temperature gradient between different zones of the same metal is regarded as thermogalvanic corrosion [20][21][22][23].…”

“…The importance of thermal gradients in contributing to corrosion of industrial equipment has been reported in numerous studies [17,[23][24][25][26][27][28][29][30]. Thermogalvanic corrosion resulting from temperature gradients can cause the early failure of copper pipes exposed to a sustained temperature gradient.…”