This paper is the first in a series of three that describe the application of emission Mössbauer spectroscopy to the in situ study of the cathodic and anodic behavior of cobalt. A brief review of the emission technique is given, along with a review of the chemical effects and Auger “after effects” that are associated with this experimental method. The surface sensitivity required to study thin anodic films was obtained by electrodepositing from 20 to 200Å thick Co57 active layers on cobalt surfaces. Emission Mössbauer spectra from Fe57 daughter (“probe”) atoms were obtained during polarization (vs. SCE) of specimens in buffered borate, pH 8.5. The specimens were free of surface oxide during cathodic polarization at −1100 mV. The spectra of specimens polarized at low passivating potentials, −100 mV, indicated the presence of both +2 and +3 charges. The +3 oxidation state of the Fe57 probe in the anodic film formed at this potential may arise from Auger after effects or chemical effects rather than from +3 states of the parent Co57. At higher passivating potentials +200 and +500 mV only the +3 oxidation state was observed. The existence of +2 oxidation state cannot be ruled out, however, because of the possibility for stabilization of defect charge states. Evidence for the +4 oxidation state in addition to +3 was found for specimens polarized at potentials in the transpassive range, +800 mV.

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The potential of aluminum wires immersed in an electrolyte was followed after abrupt straining of 1.5–12%. The maximum potential achieved after straining in 0.1M NaCl decreased with decrease in pH and the rate of decay to the initial steady-state value was independent of pH over the range of 1.5–6.5. The presence of dissolved oxygen in the solution increased the rate of decay to the steady-state value. The different potential behavior of untreated wires, wires heated in boiling water, and anodized wires was attributed to different mechanical properties of the oxide. The strain electrometry curves were identical in solutions of NaCl, Na2SO4, sodium tartrate, and Na2Cr2O7 of equal ionic strength. The pertinence of the results to the behavior of aluminum exposed at the tip of a growing stress corrosion crack is discussed.