The role of goethite in the formation of the protective corrosion layer on steels

The corrosion products formed on carbon and weathering steels exposed in marine, industrial and rural environments in the United States for 16 years have been investigated using M?ssbauer spectroscopy, Raman spectrometry and chemical analysis. M?ssbauer spectroscopy was used to measure the fraction of each oxide in the corrosion coatings and micro-Raman spectrometry was used to locate and map the oxides to 2 μm spatial resolution. M?ssbauer spectroscopy identified the corrosion products in the weathering steels as 75% goethite, 20% lepidocrocite and 5% maghemite. Raman analysis showed that the corrosion products generally formed as alternating layers containing different oxides. For the weathering steels the protective inner-layer closest to the steel substrate consisted of nano-sized goethite ranging in size from 5–30 nm and having a mean particle size of about 12 nm. The outer-layer close to the coating surface, consisted of lepidocrocite and goethite with the former oxide being most abundant. Electron probe micro-analysis measured significant chromium in the goethite close to the steel substrate. Comparison of the goethite in the corrosion products was made with synthetic chromium substituted goethite with nearly identical microstructural characteristics being recorded. It is concluded that chromium inclusions in the goethite are important for formation of a nano-phase oxide layer which may help protect the weathering steel from further corrosion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of EIS characteristics of CO2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO₂ corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO₂ corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical impedance spectra. Additionally, pitting of N80 steel could lead to additional capacitive reactance in impedance spectrum. The ion diffusion coefficient in corrosion scale and porosity of corrosion scale could be calculated by Warburg impedance coefficient, the results shown that the value of H⁺ diffusion coefficient in N80 and 4Cr corrosion scale is (3.46 and 1.76) × 10⁻¹⁰ m² s⁻¹, respectively. The protective ability of 4Cr corrosion scale was better than that of N80 corrosion scale.     

Cooling Water System Monitoring by Means of Mossbauer Spectroscopy

Mossbauer spectroscopy have been applied to the analysis of corrosion sediments formed on mild steel coupons, which were placed in the different points of the Bourgas Petrochemical Plant Recilculating Cooling Water System. It was shown that the created corrosion products can successfully reflect the ambient water medium pollution to which the coupons were exposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Elemental depth imaging of solutions for monitoring corrosion process of steel sheet by confocal micro X‐ray fluorescence

Non‐destructive and non‐contact analysis has been in demand on numerous occasions. Confocal micro X‐ray fluorescence analysis enables depth‐selective elemental analysis of solid samples in the laboratory. In this paper, we applied this technique for imaging elemental distributions in solutions. A low‐carbon steel sheet was placed in artificial seawater (NaCl: 3.5 mass%), and the corrosion process in the solution was observed. A depth image of Fe Kα intensity in the NaCl solution was obtained by using this technique. The Fe Kα intensity in the solution was measured with corrosion time by sequential line analysis at a fixed lateral position. The corrosion of Fe from the steel sheet, the migration of Fe ions in solution, and their condensation near a polymer window were successfully monitored. Copyright © 2014 John Wiley & Sons, Ltd.     

高速钢牌号元素的看谱检测方法

看谱检测是利用看谱仪，双照光谱图和分析标志表，对样品发射的光谱线进行目视评定，实现检测样品元素及含量的一门应用技术，本文采用光栅波长同步光谱图和定量分析标志表，对高速钢牌号中Ｗ、Ｍｏ、Ｃｒ，Ｖ，Ｃｏ元素进行定量分析试验，其测定值符合ＧＢ２２２－８４标准。本方法具有现场检测，操作简便，成本低，不取样，不损坏样品，精度高，快速，分析范围宽及分析不受钢中元素干扰等特点。     

The spectroscopy of ion-induced photon emission and its application to quantitative surface analysis

Experimentally observed photon spectra produced by ion bombardment of transition elements Sc, Ti, V, Cr, Fe, Ni, and Cu and Zn with Ar⁺ ions are very similar to arc spectra of these same elements, with respect to relative intensities of lines observed. Standard spectrochemical analysis techniques, based on the assumption of local thermodynamic equilibrium in the arc plasma, have been applied to the spectra of the pure elements, to determine the effective arc temperature under relatively clean conditions and in an oxygen environment. These techniques have then been applied to the analysis of a stainless steel sample, again under relatively clean and oxygen environments. In order to explain differences in the $\text{Fe}\text{Cr}$ ratios measured, the behaviour of the intensities of the Fe and Cr emission has been investigated as a function of the oxygen background pressure. The results indicate that while analysis is possible the results depend on the oxygen background pressure.     

液态锡对低活化马氏体/铁素体钢CLF-1的腐蚀行为研究

采用背散射电子扫描显微镜、电子衍射能谱和X射线衍射等分析方法，研究了浸泡在300~700℃的液态锡(Sn)中24h后的低活化马氏体/铁素体钢CLF-1的腐蚀行为。研究结果表明，在所有测试温度下液态锡对CLF-1钢表面均有不同程度的腐蚀，主要腐蚀机制为化合溶解腐蚀。铬(Cr)以单质形式溶解沉淀，液态锡与铁在CLF-1钢表面反应生成由铁锡化合物构成的腐蚀层。当温度低于500℃时，腐蚀层厚度近似为一常量，约8μm，化学成分为FeSn₂。当温度高于500℃时，腐蚀层厚度随温度线性增加，腐蚀层呈双层结构，分别为CLF-1边界处的FeSn层和覆盖在其表面的FeSn₂层。     

Corrosion behavior and composition analysis of chromate passive film on electroless Ni-P coating

A passive film was formed on electroless Ni-P coating (ENPC) in a bath of K₂Cr₂O₇ 30 g/l. XPS and electrochemical methods were employed to analyze its chemical compositions and corrosion behaviors. The potentiodynamic polarization tests indicated the corrosion current of the passivated sample was 1/30 that of as-plated ENPC. The XPS analysis illustrated the film comprised Cr, Ni and O. The film thickness was evaluated to be a few nanometers according to the sputtering rate of Ar⁺ ion. High-resolution XPS spectra suggested that the detected Cr in film was in the form of trivalent compounds, Cr₂O₃ and Cr(OH)₃.     

Solid state 33S NMR of inorganic sulfides

Solid state 33S NMR spectra of a variety of inorganic sulfides have been obtained at magnetic field strengths of 4.7 and 17.6T. Spectra acquired with magic angle spinning show considerable improvements in sensitivity and resolution when compared with static spectra. Multiple factors are considered when analyzing the spectral line widths, including; magnetic field inhomogeneity, dipolar coupling, chemical shift anisotropy, chemical shift dispersion (CSD), T(2) relaxation, and quadrupolar coupling. Quadrupolar coupling was expected to be the dominant line broadening mechanism. However, for most of the samples CSD was the prevailing line broadening mechanism. Thus, for many of the metal sulfides studied at a high magnetic field strength, the line widths were actually larger than those observed in the spectra at low field. This is atypical in solid state 33S NMR. Solid state 33S spin-lattice (T(1)) and spin-spin (T(2)) relaxation rates were measured for the first time and are discussed. This information will be useful in future efforts to use 33S NMR in the compositional and structural analysis of sulfur containing materials.     

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni

Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of their 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. Our previous paper [M.C. Biesinger et al., Appl. Surf. Sci. 257 (2010) 887-898.] in which we examined Sc, Ti, V, Cu and Zn species, has shown that all the values of the spectral fitting parameters for each specific species, i.e. binding energy (eV), full wide at half maximum (FWHM) value (eV) for each pass energy, spin-orbit splitting values and asymmetric peak shape fitting parameters, are not all normally provided in the literature and data bases, and are necessary for reproducible, quantitative chemical state analysis. A more consistent, practical and effective approach to curve fitting was developed based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of literature references and (3) specific literature references where fitting procedures are available. This paper extends this approach to the chemical states of Cr, Mn, Fe, Co and Ni metals, and various oxides and hydroxides where intense, complex multiplet splitting in many of the chemical states of these elements poses unique difficulties for chemical state analysis. The curve fitting procedures proposed use the same criteria as proposed previously but with the additional complexity of fitting of multiplet split spectra which has been done based on spectra of numerous reference materials and theoretical XPS modeling of these transition metal species. Binding energies, FWHM values, asymmetric peak shape fitting parameters, multiplet peak separation and peak area percentages are presented. The procedures developed can be utilized to remove uncertainties in the analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.     

Influence of Cu and Ni on the morphology and composition of the rust layer of steels exposed to industrial environment

Four samples of steels with alloying elements were exposed to an industrial environment during 1,955 days, aiming to elucidate the effect of the alloying elements Cu and Ni on the resistance of weathering steels to corrosion processes. The samples were characterized with optical microscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), saturation magnetization measurements and with energy dispersive (EDS), infrared, Mössbauer and Raman spectroscopies. All the steels originated orange and dark corrosion layers; their thicknesses were determined from the SEM images. EDS data of such rust layers showed that the alloying element content decreases from the steel core towards the outer part of the rust layer. Moreover, in the dark rust layer some light-gray regions were identified in the W and Cu-alloy steel, where relatively higher Cr and Cu contents were found. XRD patterns, infrared, Raman and Mössbauer spectra (298, 110 and 4 K) indicated that the corrosion products are qualitatively the same, containing lepidocrocite (γFeOOH; hereinafter, it may be referred to as simply L), goethite (αFeOOH; G), feroxyhite (δ′FeOOH; F), hematite (αFe₂O₃; H) and magnetite (Fe₃O₄; M) in all samples; this composition does not depend upon the steel type, but their relative concentrations is related to the alloying element. Mössbauer data reveal the presence of (super)paramagnetic iron oxides in the corrosion products. Saturation magnetization measurements suggest that feroxyhite may be an occurring ferrimagnetic phase in the rust layer.     

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.     

Experimental simulation of possible radiation-corrosive processes in container with spent nuclear fuel after groundwater ingress

Radiation corrosion in deaerated water/carbon steel systems has been studied. Kinetics of releasing corrosion products into the water and their sorption on the surface of steel tablets is affected by various factors (redox potential, absorbed dose, temperature, irradiation duration). Concentration of corrosion products in the solution was evaluated using various chemical methods. Total concentration of Fe²⁺/Fe³⁺ ions in liquid phase was determined by UV/VIS spectrometry. Solid phase was analysed using X-ray diffraction method. Corrosion processes were studied in deaerated distilled water and synthetic granitic water. Corrosion cells consisted of glass ampoules with inserted steel tablets, completely filled with deoxygenated water. Corrosion cells were carefully enclosed so that air diffusion into system during experiment was kept at minimum. ⁶⁰Co gamma sources with various dose rates were used for irradiation. The obtained results indicated that radiation noticeably contributed to the formation of corrosion products. Kinetics of radiation corrosion was strongly dependent on the parameters under study. The obtained experimental data should be taken into consideration when predicting effects of corrosion on containers with spent nuclear fuel using mathematical models.     

XAFS spectra from X-ray fluorescence Kβ line using conventional energy-discriminating detector

X-ray fluorescence spectra of copper (Cu) metal, copper monoxide (CuO), and potassium chromate (K₂CrO₄) were recorded as a function of incident X-ray energy near the Cu K-edge and chromium (Cr) K-edge, respectively, using a conventional silicon drift detector. The spectra contained components due to elastic, inelastic, and multiple scattering, in addition to the Kα and Kβ lines. Cu and Cr K-edge X-ray absorption fine structure (XAFS) spectra of Cu, CuO, and K₂CrO₄ were obtained by an intensity analysis of the Kα and Kβ lines. The intensity of the Kβ line for the different incident photon energies was obtained by numerically removing the additional scattering components using the MUSCAT program. These spectra exhibited a jump near the K absorption edges, which reproduced the spectral features obtained in transmission mode for both Cu, CuO, and K₂CrO₄. A chemical shift was also clearly identified in the X-ray absorption near edges structure using the X-ray fluorescence Kβ line. In addition, the Cr K-edge extended XAFS spectrum of K₂CrO₄ was clearly observed using the Cr Kβ fluorescent line. The XAFS measurements on the Kα and Kβ lines are possible, and they carry equally valuable information.     

Biopolymer Corrosion Inhibition of Mild Steel: Electrochemical/Mössbauer Results

Metallic corrosion is the destructive attack of a metal by its environment. Organic inhibitors, amongst others, adsorb directly onto the surface of the metal and can thus inhibit corrosion. Chitosan, tri-methyl chitosan and dodecyl amine hydrochloride were studied with a view to assessing their potential use as adsorption inhibitors for mild steel in acid chloride and sulphate solutions. The inhibition efficiency was studied successfully by potentiostatic polarisation (Tafel plots), Mössbauer spectroscopy (CEMS and transmission) and corrosion experiments in static acidified electrolytes. Inhibition efficiencies ranged from 20 to 93%. The chemical compositions of the corrosion products were determined by means of Mössbauer spectroscopy, which identified iron hydroxides as the main corrosion products forming in the presence of the inhibitors.     

山东省焦家式金矿区土壤重金属铬高光谱监测研究

矿区土壤环境问题日益突出,以山东省烟台市焦家式金矿区为典型区,系统采集了85个表层土壤样品进行野外光谱实测,其中35份用于重金属铬含量测定。利用光谱变换技术对原始光谱提取了一阶微分、二阶微分和去包络线三种光谱指标,采用偏最小二乘回归法建立光谱数据与铬含量间的定量关系,将最优预测模型应用于其余50个样本点铬浓度值的获取,最终通过克里金插值实现了对研究区土壤重金属铬的快速监测。结果表明,基于一阶微分数据模型预测精度最高,其次为二阶微分,原始光谱和去包络线数据。研究区铬的含量与金矿的分布情况密切相关,即金矿密集区域铬含量更高,这表明金矿开采对土壤中铬的含量与分布存在一定影响。     

In situ characterization of localized corrosion of stainless steel by scanning electrochemical microscope

Scanning electrochemical microscopy (SECM) area scan measurements have been performed to investigate the localized corrosion of type 304 stainless steel in neutral chloride solution. Variations in the Faradaic current measured at selected tip potential values can be related to changes in the local concentration and electrochemical activities of electroactive species involved in corrosion reactions occurring at the substrate as a function of immersion times of the substrate and polarized currents or potentials applied on the substrate. To further verify the results acquired from cyclic voltammetric experiments, SECM measurements were employed to in situ study the compositions and electrochemical activity distribution profile of the pitting corrosion products of stainless steel. It has been demonstrated that the combination of feedback current mode with generation-collection (G-C) mode of SECM is suitable to elucidate the possible reaction mechanisms and paths involved in the localize corrosion of stainless steel in neutral chloride solution.     

Physicochemical Studies on Solid Products of Reactions of Chromyl Chloride and Chromyl Acetate with Alkylaromatics. Part II. Electronic Absorption Spectra

The electronic absorption spectra of some chromium(IV) complexes as the products of chromyl chloride and chromyl acetate reaction with alkylaromatics have been studied in some organic solvents. A detailed computer analysis of the spectra including resolution into component bands as well as calculation of crystal field parameter Dq, Racah's parameter B and Franck-Condon analysis of the vibronically structured charge-transfer O—Cr band have been performed. The solvent effect on the Dq parameter has been established.     

Mössbauer spectroscopic study on glaze of pottery

Iron-barium glaze was prepared from commercially available materials for ceramic arts and from chemical reagents, and investigated by means of Mössbauer spectroscopy and an electron probe micro analyzer (EPMA). Mössbauer spectra showed a doublet of paramagnetic high-spin Fe(II) and Fe(III) incorporated into aluminosilicate, and the magnetically-split hyperfine structures of hematite and magnetite, depending on the iron content and firing conditions. The EPMA indicated striped patterns on the secondary electron images, and the fluorescent X-ray analysis proved that the patterns are due to the heterogeneous distribution of elements in the glaze.     

High temperature corrosion behaviour of some Fe-, Co- and Ni-base superalloys in the presence of Y2O3 as inhibitor

High temperature corrosion is accelerated degradation of materials at higher temperatures of operation caused by the presence of a deposit of salt or ash. Inhibitors and fuel additives have been investigated with varying success to control this type of corrosion. In this work, effect of an oxide additive namely Y₂O₃ on the hot corrosion behaviour of some superalloys viz Superfer 800H (alloy A), Superco 605 (alloy B) and Superni 75 (alloy C) has been investigated in an Na₂SO₄-60%V₂O₅ environment at 900 °C for 50 cycles. Each cycle consisted of 1 h heating in a Silicon Carbide Tube Furnace followed by 20 min cooling in ambient air. Weight data were taken by an electronic balance having an accuracy of 0.01 mg after each cycle. Subsequently, the exposed alloys were characterized by XRD, SEM and EPMA analyses to evaluate the role of the oxide additive. In the Na₂SO₄-60%V₂O₅ environment, the corrosion rate for the Co-base alloy was found to be highest, whereas that for the Ni-base Superni 75 the lowest. Superficially applied Y₂O₃ was observed to be useful in reducing the high temperature corrosion of the alloys. It was found to be most effective for the alloy A for which the oxide scale was continuous and rich in protective Cr. Alloy B showed the formation of medium size scale rich in Cr and Co. The oxide scale for the alloy C contained mainly Cr and Ni.