Electrochemical corrosion and film analysis studies of Fe and Fe- 18Cr in 1N H2SO4.
Driscoll-TJ; Covino-BS Jr.; Rosen-M
Avondale, MD: U.S. Department of the Interior, Bureau of Mines, RI 8378, 1979 Jan; :1-33
The electrochemical polarization behavior of Fe and Fe-18Cr has been characterized in rigorously controlled 1N H2SO4 solutions stirred with oxygen or an inert gas. Samples that underwent various levels of corrosion or passivation were examined using auger electron spectroscopy (aes) and ion sputtering. Passivation of iron occurred at a potential of approximately 0.6 Volt (1) in poorly stirred, oxygen-saturated solutions for forward polarization (scanning from cathodic to anodic potentials); (2) in ph-adjusted (increased), well-stirred, oxygen-saturated solutions for forward polarization; and (3) in well- and poorly stirred, oxygen- and helium-saturated solutions for reverse polarization. Passivation of Fe-18Cr occurred at a potential of approximately -0.1 Volt in helium-, nitrogen-, and oxygen-saturated solutions for all cases of forward polarization and most cases of reverse polarization. Elemental depth profiles indicated that films or adsorbed species were present on iron samples in solution subjected to open-circuit, active, and transpassive corrosion, cathodic reduction, and passivation. This conclusion was reached by considering the distribution of the solution species, primarily sulfur, in the films. Sulfur was present throughout the films on actively corroding samples, in the outer regions of films of passive and transpassive samples, and on the film surfaces of open-circuit and cathodically reduced samples.
IH; Report of Investigations
NTIS Accession No.
Avondale, MD: U.S. Department of the Interior, Bureau of Mines, RI 8378