Roles of Interstitial Nitrogen, Carbon, and Boron in Steel Corrosion: Generation of Oxyanions and Stabilization of Electronic Structure

Abstract

The effects of N, C, and B interstitials on the corrosion resistance of Fe were investigated in chloride-free boric-borate solutions at pH 6.0 and 8.0. In potentiodynamic polarization at pH 8.0, the anodic dissolution resistance of Fe-0.3N and Fe-0.3C in the active and passive regions was higher than that of pure Fe. NH 4 + and NO 2 − are considered to be dissolved chemical species that contribute to the higher corrosion resistance of Fe-0.3N. Potentiodynamic polarization measurements in a solution with HCO 3 − indicated that HCO 3 − also decreases the anodic current densities in the active and passive regions, suggesting that the formation of HCO 3 − contributes to the higher corrosion resistance of Fe-0.3C. First-principles calculations showed that the presence of N, C, and B in the Fe-lattice decreases the electronic density of states (DOS) at and near the Fermi level. The consistency between the active dissolution rates and the DOS at and near the Fermi levels of the specimens suggests that the more stable electronic structures occurred by the presence of N and C also result in the suppression of active dissolution of Fe. For Fe-0.3B and Fe-0.006B, the presence of iron boride precipitates promoted localized corrosion.

Influence of Ce Addition on Microstructure and Corrosion Resistance of 2101 Duplex Stainless Steel

“…[ 29 ] On the other hand, the stable electronic structure related to N inhibits the dissolution of steel. [ 30 ] Pitting corrosion is hindered by the austenite phase when it expands into the lace corrosion morphology. This is consistent with the results of Newman.…”

Effects of Alloying Elements and Microstructure on Stainless Steel Corrosion: A Review

“…Conversely, the high active energy was attributed to lattice/self‐diffusion mechanisms, causing occupation of B at substitutional sites. Kadowaki et al [ 56 ] systematically studied the effect of interstitial N, C, and B on steels, including Fe‐0.3N, Fe‐0.3C, Fe‐0.3B, and Fe‐0.006B samples, based on macroscale potentiodynamic anodic polarization, micro‐scale potentiodynamic polarization, and first‐principle calculations. The electrolyte was a chloride‐free boric‐borate solution with pH 6.0 and 8.0.…”

“…Reproduced under terms of the CC‐BY license. [ 56 ] Copyright 2020, The Authors, publishing by IOP Publishing. d) The comparison of potential‐pH diagrams for Fe, Cr, and interstitial N. Reproduced with permission.…”

“…Relevant studies have also been conducted on martensite. Kadowaki et al [ 56 ] studied the beneficial effects of interstitial C on martensite steel. The C content in this steel is ≈0.3 wt%, which is significantly lower than the solubility limits of C in austenite at 1323 K (≈2 wt%).…”

“…3) Electronic structure stabilization effect of interstitial N. Kadowaki et al [ 56 ] reported that Fe‐0.3N exhibited a higher resistance than pure Fe. This is attributed to the dissolved chemical species of N. , , and could be thermodynamically stable under specific conditions.…”