Mixture Of Cr Research Articles

Characterization of mechanically alloyed Fe–Cr–Sn alloys

Ferritic steels with high Cr concentration are extensively used due to their resistance to corrosion, also they are much cheaper to produce than Ni alloys and austenitic stainless steels. However, the formation of the sigma phase and phase separation affect their mechanical properties deleteriously. The addition of Sn to the Fe–Cr system retards the sigma phase formation. Their mechanical properties may be further improved by decreasing the average grain size and the density of defects inside the grains, as in nano-grained Fe–Cr alloys. Nanocrystaline Fe–Cr–Sn alloys, which are prepared by mechanical alloying, are thus, worthy of investigation. In this work mechanical alloying of mixtures of elemental Fe, Cr and Sn powders was carried out in an Ar atmosphere using either untreated or hardened vials and balls, in order to obtain the following alloys: Fe 55- x Cr 45Sn x with x = 0, 3 and 6 at%. These were studied by 57Fe Mössbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). It was found that the increasing of the Sn concentration leads to a reduction of particle size and grain size. Furthermore, milling in the untreated vials causes a partial amorphization of the alloys. Contamination from the balls and vials decreases with the increasing Sn concentration.

Mössbauer and TEM study of Fe–Cr powders elaborated by mechanical alloying

A Cr 80Fe 20 alloy was elaborated by mechanical alloying, in a planetary mill, from powder mixture of elemental Fe and Cr. Mössbauer spectrometry was performed to follow the formation of the alloy which is paramagnetic at 300 K. The weight of the magnetic contribution due to the uncompletely alloyed α-Fe, decreases linearly with the milling time. Powder particle microstructure was studied by TEM. The micrometer particles consist of nanocrystalline grains of about 5–15 nm. After 12 h of milling, the Cr 80Fe 20 alloy seems to be highly disordered than after 3 h.

Electron Probe Microanalysis (EPMA) Characterization of Scales Formed on Laves Phase Reinforced Cr Alloys at 1100°C in Air

Abstract Laves phase (Cr2X) strengthened Cr solid solution [Cr(X)]-based alloys are under development for a variety of high-temperature structural applications. Among the most promising alloys are castings based on the Cr(Ta)-Cr2Ta eutectic, which exhibit room-temperature fracture toughness in the 10-12 MPa√m range and creep rupture lives in excess of 1000 h at 1000° (138 MPa) in air. These alloys exhibit superior high-temperature oxidation resistance to previously developed Cr(Nb)-Cr2 Nb based alloys despite the general similarities of Ta and Nb. In order to optimize high-temperature oxidation resistance an understanding of why the Cr(Ta)-Cr2Ta alloys are more oxidation resistant is needed. Detailed EPMA characterization of the oxidized scaleswas initiated as a first steptowards gaining this understanding. Fig. 1 shows a backscattered electron image of cast and heat treated and heat treated Cr-10Nb at.% after a 6 cycle, 120 h exposure at 1100°C in humid air. Most of the coupon was converted to a complex mixture of Cr-, Nb-, and Cr+ Nb- oxides.

In situ Detection of Chromate Using Photoacoustic Spectroscopy

Pulsed-laser photoacoustic spectroscopy (LPAS) can be used to non-destructively assay aqueous Cr(VI) concentrations at trace levels. The technique involves the absorption of light pulses at 371 nm by Cr(VI) species (predominately chromate and bichromate). The absorbed energy is subsequently released in the form of heat generating a local pressure wave that is detected by an ultrasonic transducer. Because the total absorptivity of a Cr(VI) solution depends on the mixture of Cr(VI) species present and, thus, is strongly correlated with pH, a simple working expression relating solution absorbance to pH was developed, and molar absorptivities for several Cr(VI) species are reported. The detection limit for Cr(VI), which is effectively determined by the absorptivity of water, is reported to be 1 ng mL−1 at pH 6. Detection limits near 0.3 ng mL−1 would be expected for solutions at pH 8 and above, where the absorptivities of Cr(VI) species are greater. The nondestructive nature of this technique makes in situ studies of trace-level Cr(VI) chemistry in small volumes possible. We show how the technique can be used to study, in essentially real time, the thermodynamics and kinetics of Cr(VI) sorption by hematite (α-Fe2O3) powder, and the effect of competing ions, such as phosphate, on these properties.

Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution.

Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

Formability of chromate conversion coating on zinc electroplated steel sheet

A conversion coating is a coating produced by chemical or electrochemical treatment of a metallic surface that gives a superficial layer. This layer which is actually a compound of the metal gives corrosion protection and guarantee paint adhesion. A chromating liquid for forming the chromate film was prepared. The solution is a mixture of Cr+6 and Cr+3 at a ratio of 1.5 to 2.0, 1-20g/l of H2S04, 1-20g/1 of HNO3, 1-20 ml NaOH and 1-10% Si oil. The solution was applied on a surface of zinc-based plated steel sheet of approximately 0.25 mm thickness and then dried. The chromate film formed on the sheet surface was approximately 0.5-1.0 I¼m in thickness. The steel sheet with chromate film was then analysed and mechanically tested. It was found that the chromate solution has better stability over wide range of pH and the formability of its film is improved whence providing a better corrosion resistivity.

Mutual solubility of Si and Ge in the Al-rich amorphous and crystalline phases

Rapidly solidified alloys of the Al-Si-TM and Al-GeTM (TM-transition metals) systems obtained by melt spinning technique were found to have wide compositional ranges for the formation of the amorphous single phase [1–5]. Moreover, such compositional ranges in the Al-Ge-TM ternary alloys are relatively close to that observed in the Al-Si-TM alloys [2, 3]. Mechanical and electrical properties of these alloys change greatly with composition [3]. Quaternary Al-Si-Fe-TM (TM= 3d transition metals) system alloys were studied recently [6, 7]. One of the widest composition ranges in the direction of Si concentration axis from 16 to 45 at % Si was obtained for Al86−x Six Fe10Cr4 alloys. The microstructure of rapidly solidified Al-Si-TM [8] and Si-Al-TM [9] alloys studied recently was found to change from homogeneously amorphous to mixed structure consisting of amorphous phase and nanocrystalline Fd3m Ge-Si solid solution by the Ge addition. However, as it will be shown in the present paper, at sufficiently low total Si and Ge concentration both these elements are dissolvable in the Al-rich amorphous phase. Ingots of Al-Si-Ge-Fe-Cr alloys were prepared by arc melting the mixture of Al (99.99%), Si (99.9999%), Ge (99.9999%), Fe (99.9%) and Cr (99.9%) in an argon atmosphere. From these alloys, ribbon samples of about 0.015–0.02 mm in thickness and 0.9 mm in width were prepared by rapid solidification of the melt on a single copper roller at the wheel surface velocity of 41.9 m s−1. The structure of ribbon samples was examined by X-ray diffraction with monochromatic CuKα radiation. Transmission electron microscopy (TEM) was carried out using a JEM 2010 microscope operating at 200 kV. Samples for TEM were polished electrolytically in a solution of 10 vol % perchloric acid and 90 vol % methanol at 208–213 K. Crystallization temperature and heat of crystallization were examined by differential scanning calorimetry (DSC) at a heating rate of 0.67 K s−1. Contrary to rapidly solidified Si-based and Ge-based alloys in which replacing of Si by Ge and Ge by Si, respectively, causes precipitation of nanocrystalline Ge particles, Al61Si25−x Gex Fe10Cr4 alloys form an amorphous phase at different x values from 0 to 25 as shown in Fig. 1. It should be mentioned, that the mixed amorphous+ nanocrystalline Ge structure also forms in Albased alloys by replacement of Al by Ge and increment of the total Si+Ge content [8]. Some characteristic features of Al61Si25−x Gex Fe10Cr4 alloys should be described. The split of the first halo peak slightly seen in the alloys containing 0–15% Ge becomes significant at higher Ge content and the left shoulder of the first halo peak marked by an arrow in Fig. 1 appears. This effect is commonly observed in Al-Ge-TM alloys and results from phase separation of the amorphous phase into Aland Ge-rich phases over a short range [2, 3]. The brightand dark-field TEM images of the Al61Si5Ge20Fe10Cr4 alloy shown in Fig. 2 exhibit modulated contrast that was observed in Al-Ge-TM alloys [2, 3] whereas the structure of the Al-Si-Fe-Cr amorphous alloys studied recently [7] is homogeneous. Although crystallization temperature very slightly changes with increase in Ge content the shape of the DSC curves shown in Fig. 3 varies greatly. Phase composition in the fully crystallized state also changes significantly in alloys containing more than 15 at % Ge. Two heat effects seen in the DSC curve of the Al61Si25Fe10Cr4 alloy (see Fig. 3) are related to the precipitation of the Fd3m Si and a quaternary (Fe,Cr)4Si4Al13 phase with a cubic structure of a= 1.260 nm [10]. The addition of 5 at % Ge causes the appearance of the small left shoulder of the second exothermic peak. During the crystallization process Ge dissolves in Si and the quaternary (Fe,Cr)4Si4Al13 phase replacing Si atoms and forming a substitutional solid solution. Lattice parameters of Si and (Fe,Cr)4Si4Al13 phase increase and the diffraction peaks relevant to these phases shift to lower 2θ angle because the atomic radius of Ge (0.123 nm) is higher than that of Si (0.117 nm) as well as the corresponding lattice parameter of pure crystalline Ge is higher than that of Si. Some unidentified

Structural investigations of chromium nitride films formed by ion beam-assisted deposition

Abstract Chromium nitride films were formed on silicon by deposition of electron beam-evaporated chromium under irradiation with nitrogen ions at an acceleration voltage of 30 kV. Cross-section TEM combined with electron diffraction showed that a multi-phase multi-layer system was formed. The formation of phase mixtures of Cr(N), Cr 2 N and CrN is mainly due to the fact that the CrN phase is only available in a very small process window owing to its narrow region of existence in the phase diagram. The CrN phase is found only in the region where the ratio of implanted nitrogen ions to deposited chromium atoms is close to unity. Owing to the large projected range of high-energy nitrogen ions in Cr and Si, a multilayer system with a nitrogen-implanted silicon substrate, an ion beam mixed zone of silicon and chromium, a nitride layer and a thin chromium metal top layer with Cr 2 N inclusions is formed.

X-ray diffractometry analysis of r.f.-magnetron-sputtered chromium/chromium nitride coatings

Abstract The effect of nitrogen content on the microstructure of chromium-based coatings deposited by r.f. magnetron sputtering was studied using various X-ray diffraction techniques. Cr, Cr 2 N and CrN were the major phases identified, respectively, for 5, 34 and 50 at.% by recording θ /2 θ and glancing incidence (1°) scans. Between these well- identified crystallographic structures, we have noted a peak broadening with poor intensities that could be interpreted as mixtures of Cr, Cr 2 N and/or Cr(N) phases. The influence of nitrogen on the preferred crystal orientation of the films was investigated. Highly textured Cr(110) and CrN (111) were evidenced, and texture was found to be a function of nitrogen content in the sputtering atmosphere. Finally, the Langford method was applied for line profile analyses leading to results concerning crystallite sizes and strains.

Improvement of the corrosion resistance of CrN coated steel by an interlayer

The electrochemical behaviour of TiN and CrN hard coatings on steel substrate is investigated. The chromium nitride coating is compared with two double layer coatings (CrN/TiN/steel and CrN/Ni/steel) with the aim of improving the corrosion resistance of the steel substrate. The transition metal nitrides TiN and CrN are deposited by using a reactive cathodic arc evaporation technology in an industrial device, while the intermediate nickel layer is deposited by an electroless process. The nitride coatings are fairly dense with a microcolumnar morphology. Adhesion is as good as usually observed with this technology. The TiN coating is characterized by a strong [111] orientation and the so-called CrN coating is in fact a mixture of Cr(N) and Cr2N or CrN nitrides. The electrochemical behaviour of the monolayer TiN or CrN is somewhat similar to an inert but porous layer overlying an active corroding substrate. The substrate is not completely isolated from the environment and the corrosion is localized through the open porosity. This corrosion mode leads to more deleterious damage than corrosion occurring on a bare substrate. In order to increase the corrosion resistance of the coated steel, a decrease in porosity is necessary. The two layer system CrN/Ni strongly improves the corrosion resistance of CrN coated steel, whereas the system CrN/TiN coating has no beneficial effect compared to the single CrN layer.

Photo Electrochemical Response of Passive Films Formed on Pure CR and Fe-Cr Alloys in Sulphuric Acid Solution

Photo electrochemical current response of passive film was investigated for pure Cr and Fe-xCr (x = 8, 14, 18) alloys polarised potentiostatically in 0.1 kmol.m -3 H 2 SO 4 solution. Photo electrochemical action spectrum could be separated into two or three constituents. These components were considered to be derived from Cr 2 O 3 (E g opt ∼3.6 eV) and Cr(OH) 3 (E g opt ∼2.5 eV), and possibly CrO OH. The optical band gap, E g opt , of each component was almost constant for various applied potentials, polarisation periods, and substrate materials. Flat band potential E fb at which the polarity of photo current changes from negative to positive with increasing potential was determined for each phase. E fb for Cr(OH) 3 on Cr and Fe-Cr alloys was about 250 mV Ag/AgCl E fb for Cr 2 O 3 was about 700 mV for Cr and about 500 mV for Fe-Cr alloys. E fb of Cr 2 O 3 for Fe-Cr alloys slightly shifted in noble direction with increasing Cr content for Fe-Cr alloys. This means a film shows both p and n type conduction properties simultaneously for some potential region Passive films ofthese metal and alloys consist ofat least two layers, that is, on the top there is Cr(OH) 3 layer, and underneath Cr 2 O 3 for pure Cr, and mixture of Cr 2 O 3 and Fe 2 O 3 for Fe-Cr alloys. Properties of Cr(OH) 3 is almost constant with increasing polarization time and potential The quantum efficiency of Cr 2 O 3 of Fe-Cr alloys increased with increasing Cr content of the substrate alloy. Therefore, the photo response of Cr 2 O 3 seems to correspond to Cr content and state in the oxide layer

The effect of heat treatment on the electrode characteristics of the ball-milled Zr–Cr–Ni

Electrodes of Zr–Cr–Ni alloys have been prepared by the ball milling process, starting from the arc-melted Zr(Cr 0.5Ni 0.5) 2 alloy and from the mixtures of elemental Zr, Cr and Ni powders. The nanocrystalline C14 structure has been obtained by either ball milling the arc-melted alloy or heat-treating the ball-milled Zr–Cr–Ni powders. The plateau pressure for hydrogenation of nanocrystalline alloys was lower than that of conventionally produced alloys. The heat-treated Zr–Cr–Ni powders showed a similar discharge capacity as the arc-melted alloy, but the activation was much easier. The structure and phase transformation occurring during the ball milling and heat-treating were analyzed and discussed.

Study of Physical Mixtures of Cr2O3−ZnO and ZSM-5 Catalysts for the Transformation of Syngas into Liquid Hydrocarbons

The effect of both the Cr/Zn atomic ratio of the Cr2O3−ZnO catalyst and the Si/Al ratio (different surface acidity) of the ZSM-5 catalyst on the activity and selectivity to gasoline is studied, whe...

Kinetic and mechanistic studies on the formation of bis(dicarboxylato)carbonatochromate(III) complexes

The reaction of the Cr(xx)2(H2O)2 − (xx = oxalate, malonate and methylmalonate) complexes with dissolved CO2 was studied by stopped-flow spectrophotometry in the 7 < pH < 9 range and between 20 to 30°C at an ionic strength of 0.5 mol dm−3 (NaCl). Under the experimental conditions the aqua complex ion consists of a pH-dependent mixture of Cr(xx)2(H2O)2 −, Cr(xx)2(OH) (H2O)2− and Cr(xx)2(OH)2 3−. The monohydroxo and dihydroxo species undergo CO2 uptake and subsequent intramolecular carbonate ligand chelation independently, at rates which are readily distinguishable and are governed by the uptake rate constants k 1 and k 2 and chelation rate constants k 3 and k 4, respectively. Only the k 1 values for oxalato, malonato and methylmalonato complexes could be calculated; k 1 = 1084 and 1333 and 1650 mol−1 dm3 s−1, respectively. The results obtained were compared with those obtained from other systems that have either cobalt(III), iridium(III) or rhodium(III) as central atoms.

Thermal expansion of Chromium (Cr) to melting temperature

In situ x-ray data on molar volumes of chromium have been collected over the temperature range from 300 K to melting. The sample was heated to melting by passing an electrical current through the sample (the technique of electrical resistance wire heating). The sample consists of a tungsten wire as a heater and a mixture of Cr and W powder, which is placed in a hole of 250 μm diameter. Tungsten was used as an internal standard for temperature determination. In order to prevent the specimen from oxidation, the experiments were carried out in an argon flow. Unit cell parameters of Cr at different temperatures were calculated using (110), (200), (211), and (220) reflections. Precision of determination of lattice parameter is 10 −4 A at 300 K and 5 10 −4 A at 2000 K. Thermal expansion of Cr increases rapidly at temperatures higher than 1200 K. The linear thermal expansion (α) of chromium between 300 and 2130 K is given by: α = 1.220(5) 10 −5 − 1.150(6) 10 −8 T + 1.132(8) 10 −6 T 2 − 0.507(7)/T 2 (T, K). In our experiments, Cr melted between 2120 and 2150 K.

Chromium(III) removal by poly(ethyleneimine) granular sorbents made by a new process of templated gel filling

By the new process of templated gel-filling (TGF), a gel-type granular sorbent has been prepared using poly(ethyleneimine) as the chelating resin, Cr 3+ as the template ion and glutaraldehyde as the crosslinking agent. The templating is found to increase the Cr(III) selectivity of the base resin PEI, in binary mixtures of Cr(III) with Cu(II), Ni(II) and Fe(III). The new TGF sorbent has, however, significant Cr(III) selectivity only relative to Ni(II), being much superior to the commercial resin Chelex-100 in this respect. The Cr(III) sorption on both these sorbents is enhanced significantly by NaCl and Na 2SO 4, the effect being more marked on the TGF sorbent which shows greater than 100% increase in Cr(III) sorption capacity in 0.5 M NaCl and 0.25 M Na 2SO 4 solution containing Cr(III) in low concentrations. The sorbent is thus suitable for removing low level chromium from strong salt solutions and has fast kinetics with a t 1 2 of 1.5 min in 2 mM Cr(III) solution.

Cr(3)Si(2)O(7).(1)/(4)MX (MX = NaCl, NaBr, KCl, KBr): A Cage Structure Built from [Cr(II)O(4)] and [Si(2)O(7)] Units(1).

The new compounds Cr(3)Si(2)O(7).(1)/(4)MX (MX = NaCl, NaBr, KCl, KBr) form a series of chromous disilicates hosting alkali-metal halides in a framework structure. Purple crystals with edge lengths up to 1 mm were prepared by reacting mixtures of Cr(2)O(3), Cr, SiO(2), and the respective alkali-metal halide in evacuated silica tubes at approximately 1620 K for 2 days. The structures of Cr(3)Si(2)O(7).(1)/(4)NaCl, Cr(3)Si(2)O(7).(1)/(4)NaBr, Cr(3)Si(2)O(7).(1)/(4)KCl and Cr(3)Si(2)O(7).(1)/(4)KBr (I4/mmm (No. 139), Z = 8, a approximately 10.3 Å, c approximately 12.97 Å) have been solved and refined from X-ray single-crystal data. The framework consists of two crystallographically independent Cr(II) in square planar oxygen coordination. Three of those squares form a bent trimer [Cr(3)O(4)O(4/2)]. Four trimers are connected through vertices forming a [Cr(12)O(24)] cage wherein the halide ion is sited. By the linking of individual [Cr(12)O(24)] units, disilicate groups form a second type of cage which is occupied by Na(+) or K(+). The disilicate groups are in eclipsed conformation with a bridging angle angle(Si,O1,Si) approximately 125 degrees. Magnetic measurements indicate strong low-dimensional antiferromagnetic interactions among the Cr(II) ions. The UV/vis spectrum of Cr(3)Si(2)O(7).(1)/(4)NaBr is reported.

The formation of chromium/nitrogen phases by nitrogen ion implantation during chromium deposition as a function of ion-to-atom arrival ratio

Nitrogen-containing phases of chromium can be formed when chromium films deposited from the vapor phase are bombarded with an intense beam of nitrogen ions. In the present paper, formation of Cr/N-phases with ion bombardment with a comparatively high ion energy is discussed. Chromium was electron beam evaporated onto silicon during bombardment with 30 keV nitrogen ions. Ion flux and atom deposition rate were varied over a wide range. At low I/A (ion-to-atom) arrival ratio, nitrogen-containing chromium films were formed. At high I/A-ratios, monophase CrN was obtained. In the transition between these phases, phase mixtures of Cr(N), Cr 2N and CrN were formed. The results show that phase formation is mainly due to ion implantation. By contrast to titanium nitride, reactions with adsorbed gases do not play a role. It turns out that phase formation follows the equilibrium phase diagrams and is a direct function of the I/A-ratio. The regions of existence of the different phases in the deposition rate / ion current density diagram are separated by iso-I/A-lines.

Differential redox and sorption of Cr (III/VI) on natural silicate and oxide minerals: EXAFS and XANES results

Synchrotron-based X-ray absorption fine structure (XAFS) spectroscopy was used to investigate the reduction of aqueous Cr(VI) to Cr(III) in magnetite-bearing soils from Cr-contaminated sites. Soils from two field sites were examined, showing that mixed-valence Cr(III/VI) effluent is reduced to Cr(III) when associated with the magnetite fraction of the soil, whereas the Cr effluent associated with non-Fe(II) -bearing minerals results in mixed Cr(III/VI) adsorbates or precipitated phases. The Fe 2+ in magnetite, Fe 2+Fe 2 3+O 4, may act as an electron source for heterogeneous Cr(VI)-to-Cr(III) reduction, converting magnetite topotactically to maghemite, γ-Fe 2 3++O 3. The ratio of Cr(VI)/total Cr was determined by the height of the Cr(VI) XAFS pre-edge feature, which is due to a is to 3d electronic transition. This pre-edge feature was calibrated as a function of Cr(VI)Cr(III) using mixtures of Cr(III) and Cr(VI) model compounds. Environmental remediation of Cr-contaminated sites requires knowledge of chromium oxidation and speciation, and XAFS spectroscopy may be used to supply both types of information with minimal sample processing or data analysis.

One-Electron Reduction of Chromium(VI) by α-Lipoic Acid and Related Hydroxyl Radical Generation, dG Hydroxylation and Nuclear Transcription Factor-κB Activation

Reaction of chromium(VI) with α-lipoic acid (reduced form, also called 1,2-dithiolane-3-pentanoic acid) generated Cr(V) and hydroxyl radical (•OH) as measured by electron spin resonance and ESR spin trapping. 5,5-Dimethyl-1-pyrroline was used as a spin trapping agent. Catalase inhibited the•OH generation and enhanced the Cr(V) formation. Superoxide dismutase had an opposite effect. H2O2enhanced the•OH generation and decreased the Cr(V) formation in a dose-dependent manner. Metal chelators, EDTA, diethylenetriaminepentaacetic acid, deferoxamine, and 1,10-phenanthroline inhibited•OH radical generation in the order of EDTA > 1,10-phenanthroline > DTPA > deferoxamine. Oxygen consumption measurements indicated that molecular oxygen was used to generate•OH radical in the mixture of Cr(VI) and α-lipoic acid. H2O2and superoxide radical (O2−) were involved as reactive intermediates. The•OH radical was generated via Cr(V)-mediated Fenton-like reaction (Cr(V) + H2O2→ Cr(VI) + OH−+•OH). HPLC measurements show that the•OH radical generated by this reaction is capable of generating 8-hydroxyl-2′-deoxyguanosine from 2-deoxyguanosine. Incubation of Cr(VI) with cultured Jurkat cells resulted in an activation of DNA binding activity of the nuclear factor (NF)-κB. Addition of α-lipoic acid enhanced the NF-κB activation, while the•OH radical scavenger, sodium formate, inhibited it, showing that α-lipoic acid enhanced Cr(VI)-induced NF-κB activation via free radical reactions. The results indicate that while α-lipoic acid is considered to be an antioxidant, it may be a cellular one-electron Cr(VI) reductant and could be involved in the mechanism of Cr(VI)-induced carcinogenesis.