Effect of Cr Content On Pitting Behavior of Fe-Cr Alloys

Abstract

Immersion and applied current studies are used to investigate the pitting behavior of binary Fe-Cr alloys formed both by conventional melting techniques and by diffusion of chromium into mild steel (chromizing). Experiments on both sets of materials show that a chromium content of 28–30 percent is critical for elimination of room-temperature pitting corrosion. It is proposed that chromium acts to improve the pitting resistance of Fe-Cr alloys by stabilizing passivity, thus reducing pit initiation and slowing pit growth. The relationship between polarization measurements and pitting is discussed. It is shown that in a simple immersion test pitting occurs at potentials quite different from the “critical” potentials predicted by polarization measurements.

Metal-Liquid Reactions: Corrosion

“…Not all investigators are convinced of the utility of such a concept, (79) although the basis of available evidence suggests that it has some engineering value. (80) 9.…”

“…These quantities are defined in Figure 95, which also suggests that corrosion fatigue and stress corrosion cracking processes may be a part ofthe same continuum. Detailed aspects of corrosion fatigue have been summarized in a recently published volume,u 79) As was necessary in considering the stress corrosion cracking of metals, distinguishing between initiation and propagation processes is also important in corrosion fatigue. The initiation process is usually defined by testing smooth specimens and determining the number of cycles to failure.…”

Studies on the Pitting Corrosion of the Delta‐52 Steel in aqueous solutions. 2. Variation of the pitting potential in relation to the concentration of the aggressive anion

“…have been usefully applied to the study of pitting corrosion (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). In presence of anions enabling pitting corrosion, the potential does not reach oxygen evolution, and the current increases steadily at lower potential, dependent on a number of factors (6)(7)(8)(9)(10)(11)(12)(13).…”

“…In presence of anions enabling pitting corrosion, the potential does not reach oxygen evolution, and the current increases steadily at lower potential, dependent on a number of factors (6)(7)(8)(9)(10)(11)(12)(13). This increase in current does not occur directly after the addition of the aggressive ion, but a certain time elapses.…”

Interpretation of electrochemically and chemically investigated corrosion behaviors of 316L SS in acid chloride environments

“…Steigerward [17] reported that pitting corrosion in the immersion tests took place at much lower potentials than the pitting potential determined by the electrochemical technique. He measured the corrosion potential after only 65 hours of exposure of Fe-Cr alloys to a 10 percent FeC136H 20 solution.…”