Chronopotentiometry and differential capacity measurements were used to study the passive films formed by anodic polarization of a series of Fe‐Cr alloys in dilute H2SO4 . Steady‐state conditions were established by electronic control of the electrode potential prior to making measurements.Cathodic reduction studies indicated the presence of at least three types of surface materials. One is nonprotective in the case of Fe and several of the lower Cr alloys, but achieves considerable stability to reduction or dissolution at an alloy composition approaching 12% Cr. Another material is essential for passivity of Fe and the alloys with Cr content less than 12% and plays an important role in the electrical properties of the films on these alloys. A third type of surface material appears as a by‐product of processes occurring in the transpassive region.In the composition range 2.70–9.02% Cr, capacity‐potential curves are quite similar and capacities follow a reciprocal relation with electrode potential over a range of potentials. Extrapolation of these data was used to obtain a relation between film thickness, dielectric constant, and charge equivalents involved in film reduction. Film dielectric constant values, calculated assuming the reduction of normal Fe2O3 , varied from 29.1 to 87.5, depending on the reduction reaction assumed. At an alloy composition approaching 12% Cr, the passive film assumes optimum protective properties. Correspondingly, humps develop in the capacity‐potential curves, and the curves shift in the direction of higher capacity values with increasing Cr content.

The measurement of charge consumed in the galvanostatic stripping of adsorbed oxygen or hydrogen from carbon‐supported platinum surfaces gave a measure of the area of platinum in contact with solution. A combination of the two methods proved superior to either used alone. The combination compensated for the charge consumed on the carbon with sufficient accuracy to permit measurements down to the region where the platinum area is 1/100 of the support area. Comparison with x‐ray diffraction measurements suggests that, with high platinum concentrations on low area carbons, standard platinum deposition techniques yield electrodes in which much of the platinum surface is not in contact with solution.

Ethane, n-butane, and n-octane are adsorbed from aqueous sulfuric acid solutions onto platinum electrodes at 0.25-0.55V vs. NHE. At potentials higher than 0.30V how fast the surface coverage builds up depends on both the rate of adsorption and the rate of anodic oxidation. At 0.25-0.30V adsorption can be studied independently. Rate data show that adsorption is potential independent and first order in apparent uncovered surface area. Studies of the kinetics of anodic oxidation and studies of hydrogen codeposition indicate that the adsorbed species are similar for ethane and n-octane but differ for n-butane adsorption.) 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 2015-04-02 to IP Phys. Chem., 69, 3335 (1965).) 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 2015-04-02 to IP