Iron Corrosion Products Research Articles

Corrosion control measures in Sweden and the effect of succession order

Corrosion control actions for drinking water distribution in Sweden are discussed. Several different processes are used. The water quality goals vary over a wide range both with respect to pH and alkalinity. None of the waters are supersaturated with respect to calcium carbonate. The results of the corrosion control action on copper and iron corrosion product release are calculated and discussed in terms of possibilities for improvements. The effect of water quality changes due to pipe material succession order is shown.

Electrochemical and spectroscopic study of arsenate removal from water using zero-valent iron media.

This study investigated the mechanisms involved in removing arsenate from drinking water supplies using zero-valent iron media. Batch experiments utilizing iron wires suspended in anaerobic arsenate solutions were performed to determine arsenate removal rates as a function of the arsenate solution concentration. Corrosion rates of the iron wires were determined as a function of elapsed time using Tafel analysis. The removal kinetics in the batch reactors were best described by a dual-rate model in which arsenate removal was pseudo-first-order at low concentrations and approached zero-order in the limit of high arsenate concentrations. The presence of arsenate decreased iron corrosion rates as compared to those in blank 3 mM CaSO4 background electrolyte solutions. However, constant corrosion rates were attained after approximately 10 days elapsed, indicating that the passivation processes had reached steady state. The cathodic Tafel slopes were the same in the arsenate and the blank electrolyte solutions. This indicates that water was the primary oxidant for iron corrosion and that arsenate did not directly oxidize the iron wires. The anodic Tafel slopes were greater in the arsenate solutions, indicating that arsenate formed complexes with iron corrosion products released at anodic sites on the iron surfaces. Ion chromatography analyses indicated that there was no measurable reduction of As(V) to As(III). X-ray absorption spectroscopy analyses indicated that all arsenic associated with the zero-valent iron surfaces was in the oxidation state. Interatomic arsenic-iron distances determined from EXAFS analyses were consistent with bidentate corner-sharing among arsenate tetrahedra and iron octahedra. Results from this study show that under conditions applicable to drinking water treatment, arsenate removal by zero-valent iron media involves surface complexation only and does not involve reduction to metallic arsenic.

Characterization of corrosion products in the permeable reactive barriers

The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well as evaluates the effect of the iron corrosion products and precipitates on iron wall performance during contaminated-water treatment under varying conditions. Major phases in the reactive iron barrier include iron oxides, carbonates, iron sulfides, and elemental sulfur, depending on the degree of iron oxidation, groundwater chemistry, and microbial activity. Detailed geochemical and mineralogical characteristics are imperative for long-range predictions of the reactive iron wall performance on water treatment because the surface coating materials reduce the effectiveness of the zero-valent iron media.

Analysis of acid returns improves efficiency of acid stimulation: a case history

Techniques are demonstrated to evaluate acid stimulation treatments based on chemical analysis of the return fluids. The techniques can provide information about the source of formation damage, the amount and type of scale in the casing, the efficiency of the acid treatment, and the amount of iron control chemicals required for similar treatments. As an example, these methods were used for the acid stimulation treatment of a typical seawater injection well (Well A) in a large carbonate reservoir in Saudi Arabia. Over a 2-day period, more than 50 field samples were collected. More than 700 chemical analyses were eventually made on these samples. Analysis of the casing pickle fluids showed that 235 kg of iron from corrosion products, as well as a significant amount of acid-insoluble iron carbide, Fe 3C, was produced. Measurement of iron (II) and iron (III) concentrations showed that the iron corrosion products in the casing contained mostly iron oxides such as rust or mill scale. The pickle treatment prevented the injection of this material into the formation around the wellbore. Otherwise, the main acid treatment would have flushed all of this material into the reservoir and reduced injectivity. Analysis of the matrix acid flowback samples showed that iron control chemical concentrations in the acid could be reduced with significant cost savings. The extent of acid dilution and the amount of unreacted acid were also determined. The results showed that 125 kg of calcium sulfate was dissolved from the near-wellbore region during flowback. Acid stimulation of Well A increased the injectivity index (II) of the well from 0.12 to 0.21 m 3/day/kPa (5 to 9 bbl/day/psi), an increase of 75%. The acid stimulation was successful and the evaluation methods provided useful information to improve the success of future treatments.

Corrosion Products of Galvanized Rebars Embedded in Chloride-Contaminated Concrete

Abstract Iron corrosion products of steel reinforcement result in staining, cracking, and spalling of concrete structures. These effects of corrosion require costly repairs and maintenance during the useful life of the structures. To prevent corrosion of important infrastructure projects, galvanized reinforcing steel occasionally is used. The performance of galvanized steel in chloride-contaminated concrete is attributed to the corrosion product form: zinc oxide (ZnO), which is less voluminous than iron corrosion products. However, zinc corrosion products detected on galvanized reinforcement are rather controversial. Some authors identified another compound: zinc hydroxychloride (Zn5[OH]8Cl2·H2O). This product occupies more space than ZnO and can induce cracking of the cover concrete. Other authors found zinc hydroxychloride and zinc hydroxide (Zn[OH]2). In this work, ZnO and Zn5(OH)8Cl2·H2O were identified. Under some conditions (exposure time in aggressive environment and coating thickness) and after cracking of concrete cover, Zn(OH)2 also was found.

Diffusion of Plutonium in Compacted Bentonites in the Reducing Condition With Corrosion Products of Iron

Diffusion of Plutonium in Compacted Bentonites in the Reducing Condition With Corrosion Products of Iron

Uranium Removal from Ground Water Using Zero Valent Iron Media

AbstractRemoval of uranium from contaminated ground water using zero valent iron is currently under evaluation at several U.S. Department of Energy (DOE) facilities. Uranium removal by zero valent iron may occur via adsorption onto iron corrosion products, and by reduction to less soluble valence states by reactions with elemental iron. This research investigated the effects of water chemistry and surface precipitate buildup on the removal of soluble uranium by zero valent iron. Batch testing was performed to assess solution chemistry effects on uranium adsorption to the potential iron corrosion products, magnetite and a mixed valent amorphous iron oxide. Uranium adsorption to the simulated iron corrosion products was highly dependent on pH, and the concentration and speciation of the background electrolyte solution. Uranium removal via reduction by elemental iron closely approximated pseudo‐first‐order removal kinetics, despite the buildup of up to 40,000 monolayers of precipitated uranium on the iron surfaces. This indicates that the rate of uranium removal is not strongly dependent on the thickness of the adsorbed uranium layer. Short‐term rates of uranium reduction were similar for all solutions tested, but long‐term rates were highly dependent on water chemistry. Compared to deionized water, uranium removal rates were increased in sodium chloride containing solutions and reduced in sodium nitrate solutions. The strong influence of water chemistry on long‐term reduction rates indicates that system design will require extnded testing with the ground water of interest.

Spatial relationships between marine bacteria and localized corrosion on polymer coated steel

Diagnosis of microbiologically influenced corrosion on iron‐containing substrata exposed in marine environments cannot be based solely on spatial relationships between large accumulations of bacterial cells and iron corrosion products. Experiments were designed to evaluate the relationship between marine bacteria and localized corrosion on coated mild steel. The distribution of bacteria was strongly influenced by the presence of iron corrosion products independent of coating combinations. In the presence of cathodic protection, coating defects were filled with calcareous deposits and few bacterial cells. The results demonstrate that bacteria are preferentially attracted to iron corrosion products in coating defects and that attraction is more influential than topography in determining the spatial distribution of bacterial cells.

Contact corrosion measurements on the pair UO 2+ x and carbon steel 1.0330 in brines and bentonite porewater with respect to direct waste disposal

Contact corrosion between carbon steel and UO 2 was studied in the MgCl 2 rich Q-brine, in bentonite porewater and in saturated NaCl solution by use of contact potential and contact current measurements. In all solutions the carbon steel dominates the contact potential, so that this potential is near to the rest potential of the carbon steel. Only in solutions without precipitation of iron corrosion products, the presence of metallic iron slightly reduces the UO 2 corrosion rate. If iron corrosion products precipitate, the relevant adsorption of the uranium species will be more effective than any direct cathodic corrosion protection.

Adsorptive Stripping Measurements of Iron Accumulation in Mice Kidney Using Microelectrodes and Histological Features

The toxic effects caused by iron in kidney was performed on experimental studies with mice following administration of a metallic solution of this species to simulate the iron corrosion products of a metallic implant. To quantify the total levels of iron present in this organ, an electrochemical method was chosen based on the application of square wave voltammetry using adsorptive collection of iron-catechol on a mercury film microelectrode (MFM). The optimal working conditions to produce a very stable and reproducible iron peak in the digested kidney samples were found to be pH = 7.2 provided by 8.0 mmol/L PIPES buffer, catechol concentration of 3.0 x 10(-4) mol/L, deposition potential -1.80 V and deposition time 20 s. These results were compared with those obtained by atomic absorption spectrometry (AAS) indicating a good performance of the electrochemical method used. The analytical results show an increase of iron concentration with treatment time, which indicates that this metal ion is partially accumulated in the kidney. This accumulation induces with time some morphological alterations as evidenced by the histological analysis.

Decontamination of TCE- and U-Rich Waters by Granular Iron: Role of Sorbed Fe(II)

Uranium (UO22+) and chlorinated aliphatics [tetrachloroethane (PCE) and trichloroethane (TCE)] can be reduced and thus immobilized or degraded (i.e., dehalogenated), respectively, by the same abiotic mechanism. In this mechanism the reduction reaction is coupled to the oxidation of Fe(II) sorbed on iron corrosion products such as hematite. This is indicated by the equilibrium Eh values measured during uranium immobilization and PCE degradation reactions of zerovalent iron. These values fit closely with those measured in the Fe(II)-αFe2O3-H2O system (in the absence of U or PCE), not those of the Fe(o)/Fe(II) or H2(g)/H2O couples. Because iron (II) is very unstable in environments that are not strictly anaerobic, Fe(o) serves as a source of Fe(II). The reduction kinetic rate, analyzed in detail for the reduction of U(VI), is found to be a function of the concentration of OH−, Fe2+ and reactive surface sites, and is given in terms of sorbed species concentrations by {d[U(VI)]ads}/dt={−k′[≡FeOFeOH0][U(VI)]ads}. This rate law applies to organic pollutants as well, as long as they can be reduced by surface Fe(II): {d[Pollutant]}/dt={−k′[≡FeOFeOH0][Pollutant]}. This mechanism suggests new possibilities for the improvement of low-cost decontamination techniques for U- and chlorinated aliphatic-rich waters.

Corrosion resistance of titanium nitride and mixed titanium/titanium nitride coatings on iron in humid SO2-containing atmospheres

The corrosion behavior in humid SO2-polluted atmospheres of three different TiN coatings on iron [single layer TiN (1000 nm), bilayer Ti(100 nm)/TiN(1000 nm) and multilayer Ti(100 nm)/TiN(100 nm)/Ti(100 nm)/TiN(100 nm)] have been investigated by means of x-ray photoelectron spectroscopy. Only the single layer coating shows some degradation in low concentration (0.001% v/v) SO2 atmospheres after 14 days of exposure, the other two coatings remaining stable. Exposure to higher SO2 concentration (0.04% v/v) for 7 days results in the total degradation of the single layer coating. Exposure to this latter atmosphere for 14 days brings about a considerable degradation of the bilayer and multilayer coatings, the results showing that the multilayer coating, even with the lowest total thickness, presents the highest resistance against these corrosion conditions. Corrosion of the TiN coatings results in the formation of TiO2 and several N species [probably of the type (NH4)2SO4 and species containing N–O bonds]. The degradation of the coatings results in the corrosion of the underlying iron. Fe2+ sulphates and sulphites, as well as FeOOH, are the main iron corrosion products.

Diffusion of Cs and Sr in Compacted Bentonites Under Reducing Conditions and in the Presence of Corrosion Products of Iron

ABSTRACTIn high-level waste repositories, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. Iron corrosion products are expected to interfere with migration of radionuclides by filling the pore in bentonite and sorbing radionuclides. In this study the apparent diffusion coefficients of cesium and strontium were measured in compacted Na-bentonites (Kunigel VI® and Kunipia F®, JAPAN) contacted with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients of cesium with and without corrosion product were 2.2 to 13 × 10−12m2/s. The apparent diffusion coefficients of strontium with and without corrosion product were 3.1 to 25 × 10−12m2/s. There were significant effects of dry density (0.8 to 2.0 g/cm3) and montmorillonite contents (50% for Kunigel V1 or 100% for Kunipia F). The presence of corrosion product decreased the apparent diffusion coefficients of Cs in both bentonites and that of Sr in Kunigel V1, especially at low dry density. This may be due to corrosion product filling the pore in the bentonite, decreasing the free pore size and density for diffusion.

Effects of Water Redox Conditions and Presence of Magnetite on Leaching of Pu and Np From HLW Glass

ABSTRACTThe objective of this study is to evaluate the effects of water redox conditions and of the presence of iron corrosion products (magnetite) on the release of actinides from HLW glasses. Static corrosion tests were performed on a simulated HLW glass doped with Pu and Np in deionized water in the presence of magnetite under oxidizing and reducing conditions. The tests under oxidizing conditions were performed in air, while the tests under reducing conditions were performed in mixed gas (Ar+5%H2) atmosphere.The following results were obtained: (1) The presence of magnetite enhances formation of colloids containing Pu and Np in the leachates under both redox conditions. (2) Redox conditions have no remarkable influence on the release of Pu. (3) The reducing conditions combined with the presence of magnetite cause a decrease in the concentrations of Np dissolved species, which is probably the result of the reduction of Np(V) to Np(IV) at the magnetite surface.

Sorption and Reduction of Uranium(VI) on Iron Corrosion Products under Reducing Saline Conditions

Sorption and Reduction of Uranium(VI) on Iron Corrosion Products under Reducing Saline Conditions

Diffusion of Technetium in Compacted Bentonites in the Reducing Condition with Corrosion Products of Iron

ABSTRACTIn the vicinity of a high-level waste repository, corrosion of carbon steel overpacks will create a reducing environment. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as technetium.The apparent diffusion coefficients of technetium were measured in compacted bentonites (Kunigel VI® and Kunipia F®, JAPAN) in contact with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients measured were 10-12to 10-13m2/s under oxidizing conditions and 10-12to 10-13m2/s under reducing conditions. There were significant effects of redox condition, dry density (0.2 to 2.3 g / cm3) and montmorillonite content (50% for Kunigel VI or 100% for Kunipia F) on the apparent diffusion coefficients. Montmorillonite density could be a good index to explain density dependence of the diffusion coefficients under both reducing and oxidizing conditions.

Diffusion of Uranium in Compacted Bentonites in the Reducing Condition with Corrosion Products of Iron

AbstractIn high-level waste repository, a carbon steel overpack will be corroded after closure. This will create a reducing environment in the vicinity of the repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as uranium.The apparent diffusion coefficients of uranium were measured in compacted bentonites (Kunigel VI® and Kunipia F®, JAPAN) in contact with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients measured were 10-12 to 10-14 m2/s under oxidizing conditions and 10-13 to 10-14 m2/s under reducing conditions. There were significant effects of redox conditions, dry density (0.8 to 2.0 g/cm3) and montmorillonite contents (60% for Kunigel VI or 100% for Kunipia F) on the apparent diffusion coefficients. The sorption of uranium on corrosion products of iron was smaller than that on montmorillonite. Montmorillonite density could be a good index to explain density dependence of the diffusion coefficients under the reducing conditions. Uranium would diffuse in free pore water with diffusion coefficients greater than 10-13 m2/s in low density bentonites under both redox conditions because the diffusion coefficients depended on sorption coefficients. Since diffusion coefficients were independent of sorption coefficients in high density bentonites where free pore water is scarce, surface diffusion might occur with coefficients were of about 10-13 m2/s.

Optimisation d'un traitement de dechloruration d'objets ferreux par plasmad'hydrogene

AbstractThe method of removing chlorides from archaeological iron objects using hydrogen plasma at low pressure has been studied and improved. To carry out the initial experiments and to limit the use of ancient material, synthetic samples were made from iron powder and corrosion products consisting mainly of akaganeite. The time and the temperature required for the complete removal of the chlorides were determined. It was also possible to demonstrate that magnetite, and iron above 400°C, are the final reaction products of the reduction of akaganeite.

Optimisation d'un traitement de dechloruration d'objets ferreux par plasma d'hydrogene

The method of removing chlorides from archaeological iron objects using hydrogen plasma at low pressure has been studied and improved. To carry out the initial experiments and to limit the use of old material, synthetic samples were made from iron powder and corrosion products consisting mainly of akaganeite. The time and the temperature required for the complete removal of the chlorides were determined. It was also possible to demonstrate that magnetite, and iron above 400°C, are the final reaction products of the reduction of akaganeite.

Corrosion of Iron and Migration of Corrosion Products in Compacted Bentonite

AbstractFor safety assessment of the geological disposal of the high level radioactive waste, it is necessary to study corrosion of the overpack materials and migration of the corrosion products in the compacted bentonite. In the present study, average corrosion rates of iron foil and apparent diffusion coefficients of the corrosion products were determined using a neutron- activated iron foil. The average corrosion rates were on the order of 10-6m/y, while apparent diffusion coefficients were in the range from 10-12 to 10-14m2/s. No tendency to decrease in the corrosion rates with increasing corrosion time was observed. This suggests that the iron foil corrodes under reducing condition. Asymmetric concentration profiles of iron corrosion products were obtained in some experiments. It can be considered that either cathodic or anodic reaction would dominantly occur on one side of the iron foil surfaces and that each reaction would change the pH in pore water of bentonite specimens adjacent to the iron foil surfaces.