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,

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PurposeMolten salt batteries are suitable for pulse power applications because of the low effective internal impedance. This paper deals with a bipolar battery having a Li alloy anode, COS, cathode material, and electrolyte of mixed Li halides. The system is semi-dry because the amount of electrolyte is limited.Fundamental investigations to determine operating voltage limits, active material utilizations, capacity ratios, states of charge, and capacity reserves need to be determined in semi-dry conditions to be unequivocal. This requirement precludes a reference electrode and, instead, the function of a counter-electrode and reference electrodes were combined. This paper describes methods and shows comparisons with literature voltammetry data and use of galvanostatic procedures. The results obtained with several Li alloys and with COS, electrodes are discussed along with application of these electrochemical design of pulse batteries. IntroductionMolten salt electrolyte batteries have become candidates for pulse power because they have low effective internal impedances l . These attributes are due in part to the electrochemical reaction rates at the elevated temperatures and enhanced further by the selection of the couples and the electrolyte.The system of interest to us includes an anode of a lithium alloy, a COS, cathode (that is reduced with the concurrent production of Li ,S) and an electrolyte of mixed binary halides having a single cation which is the Lit ion. The laws of conservation of matter and charge precludes concentration gradients in the electrolyte2.Deploying this electrochemical system in a bipolar arrangement minimizes both ohmic drops in the intercell connections and weight because the cell wall serves the dual function of wall and intercell connector. As an intercell connector the bipolar wall has a large cross sectional area and a short length resulting in minimization of the ohmic drop3.The bipolar arrangement requires that a common electrolyte pathway between cells in aseries stack be avoided; such afault gives rise to intercell leakage currents causing non-uniformities between cells. Making the cells semi-dry, and treating the bipolar wall edge minimizes electrolyte creep thereby preventing the establishment of common electrolyte pathways. The semi-dry concepr was originally used to stabilize the nonbonded separator. In the experimental work here the separator consists of a pressed pellet of MgO and electrolyte. The anode and cathode were similarly made of active material and electrolyte which were pelletized.Molten salt batteries have been modeled for pulse power applications5 with inductive loads and for capacitative charging. In order to study discharge of the several plateaus and the subsequent charging to increase energy and power outputs, some additional information is needed.Voltage limits on charge are necessary to avoid electrolysis. Similarly, voltage limits on discharge set the electrochemical processes of each electrode within the cell.Modified constant potential charges are envi...

Common electrolyte paths in bipolar batteries waste capacity and energy via shunt currents. Historically, the degree of loss has been determined by (i) estimation using electrical analogues, (ii) measurement of magnetic fields around cell channels, or (iii) measuring voltages along electrolyte channels and manifolds. Critical review raised questions about these historical approaches. Experiments subsequently supported the criticisms and the questions. Consideration was given to charge transfer at electrodes, coupling of anodic and cathodic processes, the nature of the charge carriers in the electrode and in the electrolyte. A special symbol for impedance to ionic flow was used. From these considerations a method of simulating shunt currents was developed. Measurements were then taken to determine bipolar leakage current between contiguous cells, and to determine other intercell currents. The bipolar cell currents were found, as expected, and measured; other intercell currents were negligible as the experiments were designed. This experimental information will be used in a subsequent paper to formulate a theoretical approach to leakage currents and to design studies of common electrolyte systems. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-11 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-11 to IP

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