Characterization of corrosion products formed on the surface of carbon steel by Raman spectroscopy

Corrosion of carbon steel in seashore salty soils containing 10, 20, and 34 wt% (saturated) water was investigated. The corrosion rate was measured and corrosion products were analyzed using Raman spectroscopy. It was found that carbon steel in the soil with 10 wt% water content had the largest corrosion rate and the corrosion was dominated by localized corrosion. The corrosion rate drops dramatically and turns to be general corrosion with increase of water content. The corrosion products in the soil with 20 and 34 wt% water content are mainly composed of α‐FeOOH, while in the soil with 10 wt% water content, the products show a delaminated structure of two layers with the inner layer mainly consisting of α‐FeOOH and the outer layer composed of Fe₂O₃ and Fe₃O₄. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface oxides produced during discharge in water ambient iron surface: A conversion electron Mössbauer spectroscopic study

Oxide layers are produced on iron surface, under discharge in water ambient, applying both anodic and cathodic potentials to iron foil. Non-stoichiometric Fe_1−xO containing different ratios of Fe³⁺ and Fe²⁺ has been detected by using CEMS. Corrosion of these samples in 0.5 M H₂SO₄ shows that, cathodically discharge treated iron foil has higher corrosion resistance as compared to the anodically treated sample. This is attributed to the microstructural differences in the Fe_1−xO_x films formed during the discharge.     

Investigation of metabolic changes in blood and tissue of mice γ-irradiated with sublethal doses by direct observation of EPR signals from Hb-NO complexes

The metabolic changes in probes of blood and tissue (spleen, liver and kidney) of mice under total γ-irradiation with the doses varied in the interval of 1–10 Gy at the dose rate of 0.073 Gy/min were studied in the early postirradiation period by ex vivo electron paramagnetic resonance (EPR). It was established that the impact with the lower dose rate leads to more intensive nitric monoxide biosynthesis in comparison with higher dose rates. In the early postirradiation period (from 2 up to 6 h), irradiation with doses higher than 2 Gy brings about an increase of the NO concentration and, hence, the appearance of nitrosyl complexes which were registered directly by EPR in blood and spleen. The observed line is identified as the signal from α-(Fe²⁺-NO)₂β(Fe³⁺)₂ or α-(Fe²⁺-NO) α(Fe²⁺)β(Fe³⁺)₂ complexes since the methemoglobin concentration also increases in comparison with the control level. The concentration of Hb-NO complexes in blood and spleen depends on the dose and individual radiosensitivity of the organism. Therefore, the intensity of the Hb-NO signal may serve as a criterion of the radiation injury level during the first hours after the irradiation. 30 h after the impact, the Hb-NO complexes were no longer detected. For the first day, the concentration of Fe³⁺-transferrin in blood increases with the dose and time passed after the irradiation. The intensity of the EPR signal from Fe³⁺-transferrin in blood may also serve as a measure of the radiation injury level.     

A CEMS Study of the Corrosion of Carbon Steel After Surface Laser Irradiation

The corrosion resistance of laser-irradiated carbon steel surfaces against SO₂-polluted atmospheres has been investigated by means of weight gain measurements and CEMS. The results show that the laser-irradiated samples present a higher corrosion resistance than the non-irradiated steel. The corrosion products are found to be superparamagnetic α-FeOOH and an amorphous Fe³⁺ oxyhydroxide. This revised version was published online in August 2006 with corrections to the Cover Date.     

57Fe-DCEMS studies of thin corrosion layers

Summary The characterization of the corrosion products formed on an⁵⁷Fe film onto a low alloy steel disc after 4 h and 8 h exposure to an artificially SO₂-polluted atmosphere has been carried out by ICEMS/DCEMS. The corrosion products found are FeSO₃·3H₂O, FeSO₄·nH₂O, a third unidentified Fe²⁺ species, an amorphous Fe³⁺ oxyhydroxide and a second Fe³⁺ species which could correspond to superparamagnetic α-FeOOH or ferrihydrite. Although the DCEM spectra recorded at different electron energies do not show dramatic differences in the relative concentrations with depth, the results suggest that FeSO₃·3H₂O is preferentially located in the inner part of the corrosion layer whilst the outer part is richer in FeSO₄·nH₂O and Fe³⁺ species. Paper presented at the ICAME-95, Rimini, 10–16 September 1995     

Corrosion resistance investigation of vanadium alloys in liquid lithium

A major concern in using vanadium alloys for first wall/blanket systems in fusion reactors is their activity with regard to nonmetallic impurities in the coolants. This paper presents the results of studying the corrosion resistance in high-purity liquid lithium (with the nitrogen and carbon content of less than 10^–3 wt %) of vanadium and vanadium alloys (V–1.86Ga, V–3.4Ga–0.62Si, V–4.81Ti–4.82Cr) both in the initial state and preliminarily irradiated with Ar+ ions with energy of 20 keV to a dose of 10²² m^–2 at an irradiation temperature of ~400°C. The degree of corrosion was estimated by measuring the changes in the weight and microhardness. Corrosion tests were carried out under static isothermal conditions at a temperature of 600°C for 400 h. The identity of corrosion mechanisms of materials both irradiated with Ar ions and not irradiated, which consisted in an insignificant penetration of nitrogen into the materials and a substantial escape of oxygen from the materials, causing the formation of a zone with a reduced microhardness near the surface, was established. The influence of the corrosive action of lithium on the surface morphology of the materials under study was found, resulting in the manifestation of grain boundaries and slip lines on the sample surface, the latter being most clearly observed in the case of preliminary irradiation with Ar ions.     

TL,OA and ESR of spessartine garnet

Thermoluminescence (TL), optical absorption (OA), electron spin resonance (ESR) and their relation to point defects in spessartine have been investigated. The TL glow curve presented four peaks at 150, 220, 260 and 335 °C. The 150 and 335 °C TL peaks growth curves presented a linear growth with radiation dose up to about 400 Gy, supralinearity above this dose, and saturation around 800–1000 Gy. The OA spectrum presented allowed spin transition bands due to Fe³⁺ and Mn²⁺ in dodecahedral environment. Absorption bands due to ultraviolet charge transfer of Fe³⁺ in octahedral and tetrahedral positions were also observed. Two ESR, a strong one around g?～?2 due to Fe³⁺ in octahedral position, and another weaker one at g?～?4 due to Fe³⁺ in tetrahedral position, have been detected. The effect of high temperature annealing (600–900 °C) before irradiation was also investigated.     

Corrosion reaction of iron exposed to the open atmosphere in the Antarctic

Within a cooperative program for the elaboration of a Latin American Map of Atmospheric Corrosion, weathering steel and mild steel samples were exposed to the Antarctic atmosphere and the corrosion products analyzed by ICEMS, XPS and XRD. Superparamagnetic -FeOOH was the main corrosion product after 24 h of exposure. Cl^– ions are found on the surface of the corroded samples by XPS.     

Surface Analysis of Inhibitor Film Formed by 4-Amino-N-(1,3-thiazol-2-yl) Benzene Sulfonamide on Carbon Steel Surface in Acidic Media

Inhibitive properties of the antibacterial sulfa drug sulfathiazole—IUPAC name being 4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide—on the corrosion of carbon steel in 1.0 M HCl solution were investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Sulfathiazole is a good adsorption inhibitor, and the inhibition efficiency increases with increasing concentration. Adsorption is spontaneous and is best described by Temkin isotherm. XPS analysis showed, at this stage, that the main product of corrosion is a nonstoichiometric Fe³⁺ oxide/oxyhydroxide consisting of a mixture of Fe₂O₃, α, and γ-FeO(OH) and/or Fe(OH)₃, where α, γ-FeO(OH) is the main phase.     

Determination of Very Slow Diffusion of Paramagnetic Ions by NMR Spectroscopy

In this paper, we propose a new method of measuring the very slow paramagnetic ion diffusion coefficient using a commercial high-resolution spectrometer. If there are distinct paramagnetic ions influencing the hydrogen nuclear magnetic relaxation time differently, their diffusion coefficients can be measured separately. A cylindrical phantom filled with Fricke xylenol gel solution and irradiated with gamma rays was used to validate the method. The Fricke xylenol gel solution was prepared with 270 Bloom porcine gelatin, the phantom was irradiated with gamma rays originated from a ⁶⁰Co source and a high-resolution 200 MHz nuclear magnetic resonance (NMR) spectrometer was used to obtain the phantom ¹H profile in the presence of a linear magnetic field gradient. By observing the temporal evolution of the phantom NMR profile, an apparent ferric ion diffusion coefficient of 0.50 μm²/ms due to ferric ions diffusion was obtained. In any medical process where the ionizing radiation is used, the dose planning and the dose delivery are the key elements for the patient safety and success of treatment. These points become even more important in modern conformal radio therapy techniques, such as stereotactic radiosurgery, where the delivered dose in a single session of treatment can be an order of magnitude higher than the regular doses of radiotherapy. Several methods have been proposed to obtain the three-dimensional (3-D) dose distribution. Recently, we proposed an alternative method for the 3-D radiation dose mapping, where the ionizing radiation modifies the local relative concentration of Fe²⁺/Fe³⁺ in a phantom containing Fricke gel and this variation is associated to the MR image intensity. The smearing of the intensity gradient is proportional to the diffusion coefficient of the Fe³⁺ and Fe²⁺ in the phantom. There are several methods for measurement of the ionic diffusion using NMR, however, they are applicable when the diffusion is not very slow.     

Thermodynamic Analysis and Crystallographic Properties of MFe2O4, MCr2O4 and MAl2O4 (M = Fe,Ni, Zn) Formed on Structural Materials in Pressurized Water Reactor Primary Circuit under Zinc and Zinc-aluminum Water Chemistry

Zinc injection technology (zinc water chemistry, ZWC) was widely applied in pressurized water reactor (PWR) primary circuits to reduce radiation buildup and improve corrosion resistance of structural materials. The simultaneous injection of zinc-aluminium (ZAWC) is a novel implement created to replace part of Zn²⁺ by Al³⁺. It was reported ZAWC can improve further corrosion resistance of carbon steels and stainless steels. However, ZAWC sometimes showed even negative effects on Nickel-alloys. In this study, mechanism of formation of oxide film on metals was investigated. The reactions of Fe²⁺ Ni²⁺ in oxide films replaced by Zn²⁺, or Fe³⁺ replaced by Al³⁺ in ZAWC were analysed. The thermodynamic data and solubility of mixed oxides (ZnFe₂O₄, ZnCr₂O₄, and ZnAl₂O₄), the products of replace reactions, were calculated. According to the Gibbs free energy difference between products and reactants, ΔGθ(T) values of the formation reaction of ZnFe₂O₄, ZnCr₂O₄, and ZnAl₂O₄ are extremely negative. Solubility of ZnAl₂O₄ is the lowest among mixed oxide products, which implies the oxide film composites of ZnAl₂O₄ may show a lower corrosion rate. In addition, the preferential formation of NiAl₂O₄ on Ni-based-alloy, under ZAWC, was discussed based on crystallographic properties of spinel, which was considered as the cause of negative effects of ZAWC on corrosion resistance of Nickel-alloys. This research provides an analytical basis for the study of thermodynamic stability of oxide films under different chemical chemistry and a theoretical basis for improving corrosion resistance of different metals and optimizing the chemical conditions of PWR primary circuit.     

Corrosion products on steel 20 in aerated hydrazine solutions: Mössbauer study

Composition of corrosion layers on steel 20 in aerated solutions with hydrazine concentrations less than 11 ppm was studied at 50, 60, and 80°C in dynamic conditions by transmission Mössbauer spectroscopy and X-ray diffraction as supplementary technique. Corrosion rates were determined by gravimetric method. A comparison with corrosion in water at 80°C was made. The observed layers have not any protective character. For 0.1 m/s linear velocity, they are composed by nonstoichiometric magnetite, (Fe_3?x O₄,x=0.02–0.04) with lepidocrocite (γ-FeOOH) as secondary phase at 50°C. Haematite (α-Fe₂O₃) is observed at 60 and 80°C with a 19 nm particle size. It becomes smaller for higher velocity (0.7 m/s).     

The magnetic phase transition in titanium oxide induced by proton irradiation

We have studied the magnetic properties of ⁵⁷Fe-doped TiO₂ compounds irradiated by proton with 0, 5 and 10 pC/μm². We have observed the enhancement of the magnetic moment, measured by superconducting quantum interference device magnetometer, with increasing proton irradiation ranging from 0 to 10 pC/μm². Mössbauer spectra of proton irradiated Ti_0.99⁵⁷Fe_0.01O₂ samples were taken at room temperature. Two sites of the wing (sextet) and the central (doublet) are shown in the spectra, which suggest the magnetically ordered phase and the paramagnetic phase, respectively. With increasing proton irradiation, the part of Fe³⁺ ions was converted to Fe²⁺ ions by compensation charge. This clearly suggests that the enhancement of magnetic moment after proton irradiation is contributed to the moment by the spin-orbit coupling of Fe²⁺ ions.     

Hard magnetic properties of anisotropic Sm-Fe-N magnets produced by compression shearing method

Anisotropic Sm-Fe-N bulk magnets were produced by the compression shearing method using a hardened steel plate and a tungsten-carbide (WC) plate. It was found that the magnets retained the original Sm₂Fe₁₇N₃ phase structure without any appreciable decomposition of the Sm₂Fe₁₇N₃ phase. The anisotropic Sm-Fe-N bulk magnet produced using a WC plate had a higher density and higher crystallographic alignment of the Sm₂Fe₁₇N₃ phase than that produced using a hardened steel plate, and exhibited high maximum energy products of 228 kJ/m³ with a high coercivity of 0.88 MA/m.     

Nature of radiation resistance of LFS oxyorthosilicate crystals doped with Ce,Sc, Ca,and Y ions

Optical and luminescence characteristics of Lu_2+2ySi_1-yO_5+y (LFS) scintillation crystals are studied before and after irradiation with doses to 45 Mrad from a ⁶⁰Co source. LFS crystals were doped with Ce³⁺, Sc³⁺, Ca²⁺, and Y³⁺ ions with various concentrations. The dependence of the radiation resistance of LFS crystals on Ce ion concentration is detected. For the crystal of composition Ce:Sc:Ca:Y:LFS, it was found that its optical transmission (OT) and pulsed cathodoluminescence (PCL) spectra before irradiation do not differ from the spectra measured after irradiation with a dose of 45 Mrad within experimental error. The nature of the radiation resistance of rare-earth lutetium oxyorthosilicates (LFS) is discussed.     

Corrosion of weathering steel and iron under wet-dry cycling conditions: Influence of the rise of temperature during the dry period

The effect of a dry-hot period on the SO₂ corrosion of weatherig steel and pure iron under wet-dry cycling was investigated. Corrosion products were identified by Mössbauer spectroscopy and X-ray powder diffraction. The formation of an intermediate corrosion layer of spm α-FeOOH only on weathering steel was the most significant result.     

Fe–Mn–Al–C Alloys: a Study of Their Corrosion Behaviour in SO2 Environments

The corrosion reaction of four Fe–Mn–Al alloys exposed to a cycling, dry–humid, SO₂ (0.001% by volume) polluted atmosphere was studied. ICEMS, XPS, AES-SAM and transmission Mössbauer spectroscopy at different temperatures were employed to characterize the corrosion products. The analytical results indicate that (i) ferrihydrite is the main component of the rust; (ii) there is an abundant presence of Mn²⁺ and SO₃ ^2–/SO₄ ^2– on the top of the corrosion layer, the concentration of SO₄ ^2– increasing with the number of cycles; and (iii) the magnetic hyperfine pattern exhibited by the series of low-temperature spectra of the rust is quite different from that observed in the rust formed under similar corrosive environments on iron and weathering steel. This latter finding is correlated with a slow rate of transformation of the Fe³⁺ species formed at the early stages of corrosion into -FeOOH, the usual final product of this type of corrosion processes. The sulphate anions, abundant inside the electrolyte during the wet periods, could be incorporated to the ferrihydrite structure being responsible for the Mössbauer spectral pattern recorded from the corrosion products at low temperatures.     

Raman and IR spectroscopy study of corrosion products on the surface of the hot‐dip galvanized steel with alkaline mud adhesion

The corrosion products formed on hot‐dip galvanized steel sheets for the automobile application with adhesion of alkaline mud containing different Cl⁻ ion contents are investigated by means of Raman and infrared (IR) spectroscopy. Results show that the Cl⁻ ion content in alkaline mud has great influence on the corrosion behavior of the galvanized steel. The Cl⁻ ions are responsible for the formation of the Zn₅Cl₂(OH)₈· H₂O layer on the surface of the steel at the early stage of corrosion. The rest of the Cl⁻ ions then penetrate and interrupt corrosion product layer resulting in pitting corrosion. Subsequently, the red corrosion product of α‐FeOOH (shaped as needle‐like structure) is formed, which then transforms into black rust of Fe₃O₄ (having a shape of slim needle). It is interesting to find out that pitting depth is inversely proportional to the Cl⁻ ion content. However, corrosion rate decreases with the increase of the Cl⁻ ions in mud. Copyright © 2009 John Wiley & Sons, Ltd.     

Electron transfer reaction in the radiation chemistry of some biologically important disulphlde compounds

It is found that some biologically important organic disulphides behave in an unique way under gamma irradiation when they are added in small amounts to the well-known Fricke dosimetry solution. On irradiation, it is noted that addition of these organic solutes reduces the G(Fe⁺² → Fe⁺³) yield instead of the usual increase found in the case of most other organic compounds. It is argued that these compounds behave as sacrificial radiation protective agents. The observation has been explained on the basis of an electron transfer reaction between the disulphides and OH radical. The resulting radical cations of these compounds then dissociate into non-chain propagating species. An attempt has been made to correlate the protective ability of such compounds towards (Fe⁺² → Fe⁺³) system with their biological radiation Drotective abilities. The electron transfer mechanism also seems to operate into their radiation protective action towards biological systems.     

Specific Features of the Structural State of Iron Ions in Iron-Containing Composites Irradiated by Fast Electrons

The present paper analyzes the valence-coordination state of iron atoms in polymer composite materials fabricated from polystyrene and iron-ore concentrates – magnetite and hematite – upon exposure to fast electrons with energy of 6.2 MeV and fluence of 10¹⁸ electrons/cm². Changes in the phase content and valence-coordination and magnetic states of iron atoms are established. After irradiation, the hematite phase is transformed into the magnetite phase with a predominance of Fe³⁺ ions with [FeO₄] coordination, and the magnetite phase forms the wüstite-type (FeO) phase in which Fe²⁺ ions are arranged in [FeO₆] coordination.