Characterization of Rust Layer Formed on Fe, Fe-Ni and Fe-Cr Alloys Exposed to Cl-Rich Environment by Cl and Fe K-Edge XANES Measurements

Abstract

Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akaganéite, lepidocrocite and magnetite. Among these iron oxides, akaganéite in particular is the major component in the rust. Additionally, the amount of akaganéite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akaganéite is generally considered to facilitate the corrosion of steel, but our results indicate that akaganéite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akaganéite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel.

Desalination of Water Using ZVI (Fe0)

“…Integrating (into Figure 8) the salinity data in Table 1 (Tables C1 and C2 This relationship confirms that it is possible for 1 g ZVM to remove >1 g NaCl [25]. This observation is consistent with a model of accretionary, polyionic, akaganeite/FeOOH nano rod formation where the bulk of the adsorbed NaCl is electrostatically bound in the hydration shells and the ionic layer surrounding each FeOOH, e.g., [22,23,25,78,79,[90][91][92][93][94][95][96][97][98][99][100]108].…”

“…Half reaction (Equation (38)) can result in a film of NaOH coating [201] the ZVI and a corrosion scale (Fe(OH)2, GR1, FeOOH) coating the ZVI [18, [68][69][70][71][72][73][74][75][76][77]87,88,93,94,96,[110][111][112]167,172,173,176,191,[202][203][204]. This model [150] results (as demonstrated in Section 4) in the amount of NaCl removed (and corrosion scale formed on the ZVI particles) being directly proportional to the inherent charge generated by ZVM TP/ZVM TPA, via the Nernst relationships [150], where [150]:…”

Experimental correlation using ANOVA and DOE studies on corrosion behavior of Fe and Ni-based alloy under different media

“…Several researchers have studied the corrosion and corrosion mitigation of Fe-Ni alloys in different aggressive media [8][9][10]. They found that increasing the Ni content in the alloy improves its corrosion resistance [10].…”

Electron transport in pure and substituted iron oxyhydroxides by small-polaron migration

“…[3][4][5][6][7][8][9] Iron oxyhydroxides are also important corrosion products in various technologies. 10 Goethite (α-FeOOH) is the most thermodynamically stable form of iron at ambient conditions in the presence of water, and is the most abundant polymorph among iron oxyhydroxides. [11][12][13][14] Goethite redox properties have been the subject of intensive experimental research, especially in the context of redox-driven phase transformations to more reduced forms of Fe (e.g., ferrous iron), 15,16 surface speciation and redox transformations of metals, 9,17,18 reductive dissolution coupled to oxidative growth, and atom exchange.…”

“…Akaganéite is also known to be the major component of corrosion products formed on Fe-steels exposed to the atmosphere. 10 Lepidocrocite was shown to play an important role in biogeochemical processes of Fe 2+ /Fe 3+ transformations. 23 Unlike goethite, however, redox properties of akaganéite and lepidocrocite have been experimentally explored to a much lesser extent.…”