Articles de revues : « Chromate resistance »

1

Cervantes, Carlos, et Simon Silver. « Plasmid chromate resistance and chromate reduction ». Plasmid 27, n^o 1 (janvier 1992) : 65–71. http://dx.doi.org/10.1016/0147-619x(92)90007-w.

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Ohtake, Hisao, Kohya Komori, Carlos Cervantes et Kiyoshi Toda. « Chromate-resistance in a chromate-reducing strain of Enterobacter cloacae ». FEMS Microbiology Letters 67, n^o 1-2 (janvier 1990) : 85–88. http://dx.doi.org/10.1111/j.1574-6968.1990.tb13841.x.

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Ohtake, H., C. Cervantes et S. Silver. « Decreased chromate uptake in Pseudomonas fluorescens carrying a chromate resistance plasmid. » Journal of Bacteriology 169, n^o 8 (1987) : 3853–56. http://dx.doi.org/10.1128/jb.169.8.3853-3856.1987.

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Alvarez, Angel H., Rafael Moreno-Sánchez et Carlos Cervantes. « Chromate Efflux by Means of the ChrA Chromate Resistance Protein from Pseudomonas aeruginosa ». Journal of Bacteriology 181, n^o 23 (1 décembre 1999) : 7398–400. http://dx.doi.org/10.1128/jb.181.23.7398-7400.1999.

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ABSTRACT Everted membrane vesicles of Pseudomonas aeruginosaPAO1 harboring plasmid pCRO616, expressing the ChrA chromate resistance protein, accumulated four times more51CrO4 2− than vesicles from plasmidless cells, indicating that a chromate efflux system functions in the resistant strain. Chromate uptake showed saturation kinetics with an apparent Km of 0.12 mM chromate and aV max of 0.5 nmol of chromate/min per mg of protein. Uptake of chromate by vesicles was dependent on NADH oxidation and was abolished by energy inhibitors and by the chromate analog sulfate. The mechanism of resistance to chromate determined by ChrA appears to be based on the active efflux of chromate driven by the membrane potential.

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Julián‐Sánchez, Adriana, César Díaz‐Pérez, Carlos Cervantes et Héctor Riveros‐Rosas. « Phylogenetic Analysis of Chromate Resistance Determinants ». FASEB Journal 22, S2 (avril 2008) : 246. http://dx.doi.org/10.1096/fasebj.22.2_supplement.246.

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Acosta-Navarrete, Yaned M., Yhoana L. León-Márquez, Karina Salinas-Herrera, Irvin E. Jácome-Galarza, Víctor Meza-Carmen, Martha I. Ramírez-Díaz et Carlos Cervantes. « Expression of the six chromate ion transporter homologues of Burkholderia xenovorans LB400 ». Microbiology 160, n^o 2 (1 février 2014) : 287–95. http://dx.doi.org/10.1099/mic.0.073783-0.

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The chromate ion transporter (CHR) superfamily comprises transporters that confer chromate resistance by extruding toxic chromate ions from cytoplasm. Burkholderia xenovorans strain LB400 has been reported to encode six CHR homologues in its multireplicon genome. We found that strain LB400 displays chromate-inducible resistance to chromate. Susceptibility tests of Escherichia coli strains transformed with cloned B. xenovorans chr genes indicated that the six genes confer chromate resistance, although under different growth conditions, and suggested that expression of chr genes is regulated by sulfate. Expression of chr genes was measured by quantitative reverse transcription-PCR (RT-qPCR) from total RNA of B. xenovorans LB400 grown under different concentrations of sulfate and exposed or not to chromate. The chr homologues displayed distinct expression levels, but showed no significant differences in transcription under the various sulfate concentrations tested, indicating that sulfate does not regulate chr gene expression in B. xenovorans. The chrA2 gene, encoded in the megaplasmid, was the only chr gene whose expression was induced by chromate and it was shown to constitute the chromate-responsive chrBACF operon. These data suggest that this determinant is mainly responsible for the B. xenovorans LB400 chromate resistance phenotype.

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Escudero-Castejon, Lidia, Sergio Sanchez-Segado, Stephen Parirenyatwa et Animesh Jha. « Formation of Chromium-Containing Molten Salt Phase during Roasting of Chromite Ore with Sodium and Potassium Hydroxides ». Journal for Manufacturing Science and Production 16, n^o 4 (1 décembre 2016) : 215–25. http://dx.doi.org/10.1515/jmsp-2016-0023.

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AbstractChromium has a wide range of applications including metals and alloys manufacturing, pigments, corrosion resistance coatings and leather tanning. The production of chromium chemicals is based on the oxidative alkali roasting of chromite ores, which leads to the formation of water-soluble alkali chromates. Previous investigations reported that when chromite is roasted with soda-ash, a molten salt containing chromium, which is mainly composed of sodium carbonate and sodium chromate (Na2CO3-Na2CrO4 binary mixture), forms under typical roasting conditions. The physical properties of the liquid phase, which are dependent on the temperature, charge and gangue compositions, play an important role on the oxidation reaction and may limit the chromate recovery by hindering the oxygen transport to the reaction interface. This investigation focuses on the alkali roasting of chromite ore at 1,000 oC using NaOH and KOH, followed by water leaching. The influence of the alkali ratio on the chromium extraction yield is analysed, and the results obtained with both hydroxides are compared. Sample characterisation and thermodynamic analysis, including phase diagrams, equilibrium calculations and computation of liquidus curves, are combined with the purpose of studying the formation of the molten salt phase under different roasting conditions and its effect on the final chromium recovery.

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Cervantes, Carlos, et Hisao Ohtake. « Plasmid-determined resistance to chromate inPseudomonas aeruginosa ». FEMS Microbiology Letters 56, n^o 2 (décembre 1988) : 173–76. http://dx.doi.org/10.1111/j.1574-6968.1988.tb03172.x.

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Guo, Rui Hua, Fang Sheng Liu et Lin Min Wang. « Research of Anti-Corrosion of Armour Steel in Surface Chromate Conversion Coating ». Advanced Materials Research 734-737 (août 2013) : 2332–37. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.2332.

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This article by orthogonal experimental method to determine the composition of chromate conversion and use of electrochemical method of electrochemical corrosion of the film discussed the substrate in different components, content, time and pH of chromate conversion coating of corrosion resistance. Orthogonal to determine the best experimental chromate conversion solution by adding the rare earth element cerium and lanthanum salt, and discuss the effects of rare earth elements cerium and lanthanum chromate conversion film on the anti-corrosion. The results show that in CrO3 5.4 g/L, NaF 0.5 g/L, K3Fe (CN)6 0.5 g/L, pH 1, conversion time is three minutes, there is a better corrosion resistance. The rare earth elements in a chromate conversion solution, La2(CO3)3 to 0.2 g/L chromate conversion coating of the anti-corrosion better.

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Branco, Rita, Ana Paula Chung, Tatiana Johnston, Volkan Gurel, Paula Morais et Anatoly Zhitkovich. « The Chromate-Inducible chrBACF Operon from the Transposable Element TnOtChr Confers Resistance to Chromium(VI) and Superoxide ». Journal of Bacteriology 190, n^o 21 (5 septembre 2008) : 6996–7003. http://dx.doi.org/10.1128/jb.00289-08.

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ABSTRACT Large-scale industrial use of chromium(VI) has resulted in widespread contamination with carcinogenic chromium(VI). The abilities of microorganisms to survive in these environments and to detoxify chromate require the presence of specific resistance systems. Here we report identification of the transposon-located (TnOtChr) chromate resistance genes from the highly tolerant strain Ochrobactrum tritici 5bvl1 surviving chromate concentrations of >50 mM. The 7,189-bp-long TnOtChr of the mixed Tn21/Tn3 transposon subfamily contains a group of chrB, chrA, chrC, and chrF genes situated between divergently transcribed resolvase and transposase genes. The chrB and chrA genes, but not chrF or chrC, were essential for establishment of high resistance in chromium-sensitive O. tritici. The chr promoter was strongly induced by chromate or dichromate, but it was completely unresponsive to Cr(III), oxidants, sulfate, or other oxyanions. Plasmid reporter experiments identified ChrB as a chromate-sensing regulator of chr expression. Induction of the chr operon suppressed accumulation of cellular Cr through the activity of a chromate efflux pump encoded by chrA. Expression of chrB, chrC, or chrF in an Escherichia coli sodA sodB double mutant restored its aerobic growth in minimal medium and conferred resistance to superoxide-generating agents menadione and paraquat. Nitroblue tetrazolium staining on native gels showed that ChrC protein had superoxide dismutase activity. TnOtChr appears to represent a mobile genetic system for the distribution of the chromate-regulated resistance operon. The presence of three genes protecting against superoxide toxicity should provide an additional survival advantage to TnOtChr-containing cells in the environments with multiple redox-active contaminants.

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Díaz-Magaña, Amada, Esther Aguilar-Barajas, Rafael Moreno-Sánchez, Martha I. Ramírez-Díaz, Héctor Riveros-Rosas, Eréndira Vargas et Carlos Cervantes. « Short-Chain Chromate Ion Transporter Proteins from Bacillus subtilis Confer Chromate Resistance in Escherichia coli ». Journal of Bacteriology 191, n^o 17 (6 juillet 2009) : 5441–45. http://dx.doi.org/10.1128/jb.00625-09.

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ABSTRACT Tandem paired genes encoding putative short-chain monodomain protein members of the chromate ion transporter (CHR) superfamily (ywrB and ywrA) were cloned from genomic DNA of Bacillus subtilis strain 168. The transcription of the paired genes, renamed chr3N and chr3C, respectively, was shown to occur via a bicistronic mRNA generated from a promoter upstream of the chr3N gene. The chr3N and chr3C genes conferred chromate resistance when expressed in Escherichia coli strain W3110. The cloned chr3N gene alone did not confer chromate resistance on E. coli, suggesting that both chr3N and chr3C genes are required for function. E. coli cells expressing paired chr3N and chr3C genes demonstrated diminished uptake of chromate compared to that by a vector-only control strain. These results suggest that short-chain CHR proteins form heterodimer transporters which efflux chromate ions from the cytoplasm.

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Peitzsch, Nicola, Günther Eberz et Dietrich H. Nies. « Alcaligenes eutrophus as a Bacterial Chromate Sensor ». Applied and Environmental Microbiology 64, n^o 2 (1 février 1998) : 453–58. http://dx.doi.org/10.1128/aem.64.2.453-458.1998.

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ABSTRACT In Alcaligenes eutrophus CH34, determinants encoding inducible resistance to chromate (chr) and to cobalt and nickel (cnr) are located adjacent to each other on plasmid pMOL28. To develop metal-sensing bacterial strains, a cloned part of plasmid pMOL28, which contains both determinants, was mutated with Tn5-lacZ. The chr::lacZfusions were specifically induced by chromium; cnr was induced best by Ni2+ but was also induced by Co2+, Mn2+, chromate, Cu2+, Cd2+, and Zn2+. The broad-host-range IncP1 plasmid pEBZ141, which contains achr::lux fusion, was constructed.A. eutrophus AE104(pEBZ141), carrying achr::lux transcriptional fusion, could be used as a biosensor for chromate when cultivated in glycerol as an optimal carbon source. Chromate and bichromate were the best inducers; induction by Cr3+ was 10 times lower, and other ions induced only a little or not at all. Interactions among induction of the chr resistance determinant, chromate reduction, chromate accumulation, and the sulfate concentration of the growth medium were demonstrated.

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TAKAHASI, Wataru. « High Corrosion Resistance Green Chromate Coating for Zinc ». Jitsumu Hyomen Gijutsu 32, n^o 6 (1985) : 264–70. http://dx.doi.org/10.4139/sfj1970.32.264.

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Ma, Ying-Fei, Jian-Feng Wu, Sheng-Yue Wang, Cheng-Ying Jiang, Yun Zhang, Su-Wei Qi, Lei Liu, Guo-Ping Zhao et Shuang-Jiang Liu. « Nucleotide Sequence of Plasmid pCNB1 from Comamonas Strain CNB-1 Reveals Novel Genetic Organization and Evolution for 4-Chloronitrobenzene Degradation ». Applied and Environmental Microbiology 73, n^o 14 (25 mai 2007) : 4477–83. http://dx.doi.org/10.1128/aem.00616-07.

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ABSTRACT The nucleotide sequence of a new plasmid pCNB1 from Comamonas sp. strain CNB-1 that degrades 4-chloronitrobenzene (4CNB) was determined. pCNB1 belongs to the IncP-1β group and is 91,181 bp in length. A total of 95 open reading frames appear to be involved in (i) the replication, maintenance, and transfer of pCNB1; (ii) resistance to arsenate and chromate; and (iii) the degradation of 4CNB. The 4CNB degradative genes and arsenate resistance genes were located on an extraordinarily large transposon (44.5 kb), proposed as TnCNB1. TnCNB1 was flanked by two IS1071 elements and represents a new member of the composite I transposon family. The 4CNB degradative genes within TnCNB1 were separated by various truncated genes and genetic homologs from other DNA molecules. Genes for chromate resistance were located on another transposon that was similar to the Tn21 transposon of the class II replicative family that is frequently responsible for the mobilization of mercury resistance genes. Resistance to arsenate and chromate were experimentally confirmed, and transcriptions of arsenate and chromate resistance genes were demonstrated by reverse transcription-PCR. These results described a new member of the IncP-1β plasmid family, and the findings suggest that gene deletion and acquisition as well as genetic rearrangement of DNA molecules happened during the evolution of the 4CNB degradation pathway on pCNB1.

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Moon, Kyung Man, Sung Yul Lee, Jae Hyun Jeong et Myeong Hoon Lee. « Corrosion Behaviors for Galvanizing, Galvalume and Chromate Treated Steels in 1% NaOH Solution ». Key Engineering Materials 744 (juillet 2017) : 217–22. http://dx.doi.org/10.4028/www.scientific.net/kem.744.217.

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The galvanized steel structures may be inevitably corroded rapidly in the case of exposed to corrosive environments for long time, and these corrosive environments has been accelerated with increasing the environmental contamination due to the rapid development of industrial society. However, since the galvanizing method have the various merits compared to surface coating treatment in economical point of view, the galvanized steel have been extensively used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and various industrial fields etc.. Therefore, it has been made an effort to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, comparison evaluation on the corrosion resistance of three types of the test specimens, that is, three samples of pure galvanizing, galvalume and chromate treatment were investigated using electrochemical methods in 1% NaOH solution. The samples of chromate treatment and of galvalume exhibited the lowest and highest corrosion current density respectively in 1% NaOHsolution. In addition, the sample of chromate treatment revealed the highest impedance at 0.01Hz, which is considered that the oxide film by chromate treatment is deposited on the surface of pure galvanizing sample. After drawing polarization curves, the corroded surface of the pure galvanizing specimen indicated pattern like as localized corrosion, moreover, the large amount of corrosive products was observed on the surface of galvalume sample. However, the smooth pattern nearly similar to general corrosion was observed at the corroded surface of the sample of chromate treatment. Consequently, it is considered that the chromate treatment is an optimum method compared to pure galvanizing and, galvalume treatment to improve corrosion resistance in 1% NaOH solution.

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Bopp, Lawrence H., et Henry L. Ehrlich. « Chromate resistance and reduction in Pseudomonas fluorescens strain LB300 ». Archives of Microbiology 150, n^o 5 (septembre 1988) : 426–31. http://dx.doi.org/10.1007/bf00422281.

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Rivera, Sonia L., Eréndira Vargas, Martha I. Ramírez-Díaz, Jesús Campos-García et Carlos Cervantes. « Genes related to chromate resistance by Pseudomonas aeruginosa PAO1 ». Antonie van Leeuwenhoek 94, n^o 2 (1 mai 2008) : 299–305. http://dx.doi.org/10.1007/s10482-008-9247-x.

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Son, Byung-Ki, Ji-Won Choi, Su-Byung Jeon et Injoon Son. « Zn–Ni Alloy Plating with Trivalent Chromate : Effects of NaF Additive Concentration and Treatment Time on Film Color, Thickness, and Electrochemical Properties ». Coatings 12, n^o 8 (11 août 2022) : 1160. http://dx.doi.org/10.3390/coatings12081160.

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Zn–Ni alloy plating is widely applied in manufacturing of automobile and construction material components because it provides better corrosion resistance and wear resistance than Zn plating. Furthermore, chromate coating treatment is gaining attention with respect to improving the corrosion resistance of Zn–Ni alloys. In this study, we investigated the effects of NaF additive concentration and treatment time on trivalent chromate coating, which has been developed as an alternative to hexavalent chromate coating. The chromate post-treatment solution used in this study comprises Cr(NO3)3·9H2O (360 g/L), CoSO4·7H2O (40 g/L), and HNO3 (35 mL/L), to which NaF is added in the concentration range of 0–30 g/L. The as-formed coating films at 1.6 pH and 60 °C treatment temperature for deposition times ranging from 30 to 120 s demonstrated a decreasing corrosion rate as the NaF concentration increased. The electrochemical and morphological analyses inferred that NaF acted as a catalyst, enhancing the rate of film formation. Furthermore, the film thickness increased with the treatment time, and the film color changed in the order of yellow, purple, and green.

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., Sikander Sultan, et Shahida Hasnain . « Plasmid Mediated Chromate Resistance in Bacteria Isolated from Industrial Waste ». Pakistan Journal of Biological Sciences 8, n^o 12 (15 novembre 2005) : 1771–77. http://dx.doi.org/10.3923/pjbs.2005.1771.1777.

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Juhnke, Susanne, Nicola Peitzsch, Nicole Hübener, Cornelia Große et Dietrich H. Nies. « New genes involved in chromate resistance inRalstonia metallidurans strain CH34 ». Archives of Microbiology 179, n^o 1 (janvier 2002) : 15–25. http://dx.doi.org/10.1007/s00203-002-0492-5.

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Wang, Shuang Hong, Yong Feng Long, Shi Lu Zhao, Cheng Qiang An et Ke Ding. « A New Chromate-Free Insulating Coating on Silicon Steel ». Advanced Materials Research 1004-1005 (août 2014) : 757–62. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.757.

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The water-based paint had been examined to prepare a new chromate-free insulating coating on silicon steels. The structure of the insulating coating was characterized by scanning electron microscopy, energy dispersive spectroscopy and infrared spectroscopy. Adhesion, high temperature annealing, and surface insulating resistance were measured. Corrosion resistance was investigated by neutral salt spray test and electrochemical test. Results exhibited that the insulating coating had excellent comprehensive performance. The adhesive level was 5B degree; the high temperature annealing test showed no coating degradation after heat treatment of 2 h at 450 °C in air or at 750 °C in nitrogen; the salt spray test showed the corrosion area was less than 2 % after the 12 h salt spray; when the coating thickness was 1.0-1.2 μm, the surface insulating resistance value was 380-420 Ω/mm2.

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Kalsoom, Asma, Rida Batool et Nazia Jamil. « Highly Cr(vi)-tolerant Staphylococcus simulans assisting chromate evacuation from tannery effluent ». Green Processing and Synthesis 10, n^o 1 (1 janvier 2021) : 295–308. http://dx.doi.org/10.1515/gps-2021-0027.

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Abstract Chromium(vi) contaminated sites have been targeted for studying highly chromate-resistant bacteria. From a total of 23 Cr(vi)-resistant bacteria isolated on Luria-Bertani agar medium supplemented with K2CrO4 (1,500 μg/mL), only one strain UT8 (Staphylococcus simulans) was able to tolerate high concentration of chromate, i.e., up to 200 mg/mL in agar medium from tannery effluent. In acetate minimal medium (AMM), it showed maximum tolerance of up to 2,500 μg/mL. Cr(vi) removal potential was 94.6% after 24 h (K2CrO4 1,500 μg/mL). Parametric conditions were optimized in AMM to attain maximum chromate removal. Exopolysaccharides extracted from bacterial cells exposed to chromate exhibited major absorption shifts from 2,500 to 500 cm−1 revealed by Fourier transform infrared spectroscopy. Energy-disperse X-ray spectroscopy further confirmed the adsorption of oxyanions to the bacterial cells. Surface topography of the Cr(vi) treated cells showed transformation into concave shape by scanning electron microscopy. The presence of resistance genes, i.e., chromate reductase (chrR) and class I integrase (intI1), further confirmed tolerance toward chromate. Microarray data analysis of transcriptional gene expression suggested upregulation of cys gene cluster under chromate exposure. Concisely, the present investigations revealed the potential of S. simulans to be an effective candidate for chromate reclamation of wastewater.

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Yao, Weitang, Tao Duan, Yuanxin Li, Liming Yang et Kui Xie. « Perovskite chromate doped with titanium for direct carbon dioxide electrolysis ». New Journal of Chemistry 39, n^o 4 (2015) : 2956–65. http://dx.doi.org/10.1039/c4nj01868k.

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Malau, Viktor, et Wisnu Hakiki. « Chromate and Molybdate Inhibitors Effects on Corrosion Charateristic of API 5L Grade B in a Brine Water Solution Containing 8 % NaCl ». Key Engineering Materials 892 (13 juillet 2021) : 115–23. http://dx.doi.org/10.4028/www.scientific.net/kem.892.115.

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Piping systems at gathering stations in the oil and gas industries often fail due to corrosion attacks from the brine water solution containing 8% NaCl that flows through the system. This solution is highly corrosive on the API 5L grade B steel pipes, thereby shortening its lifespan, with an increase in the frequency of pipe replacements. However, the corrosion resistance of API 5L grade B pipes can be improved by using chromate and molybdate inhibitors. Therefore, the objective of this research is to improve the corrosion resistance of the steel pipes using sodium chromate (Na2CrO4) and sodium molybdate (Na2MoO4) inhibitors with concentrations of 0.2, 0.4, 0.6, 0.8 and 1,0%. This research also aim to determine the optimum concentration of inhibitors to produce minimum corrosion rate, by testing the brine water solution containing 8% NaCl through the potentiodynamic polarization method. The results show that generally, the addition of sodium chromate and sodium molybdate inhibitors to the brine solution causes the steel pipes to be more resistant to corrosion. Furthermore, the sodium chromate inhibitor concentration of 0.6% produces the greatest corrosion potential of – 400 mV with the lowest rate of 0.38 mpy, while sodium molybdate concentration of 0.4% produces the highest corrosion potential of – 385 mV with the lowest rate of 0.34 mpy. The results of SEM observations at 0.4% sodium molybdate concentration showed that the corrosion inhibition/passivation effect of the inhibitor made the steel surface smoother, while the sodium chromate inhibitor at similar percentage failed to reach the optimal concentration to inhibit the corrosion process.

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Pan, Qi, Lin Wu, De Lian Yi, Zhao Hui, Ou Yang, Dan Li, Xiang Nan Meng et De Ju Wang. « Research of Organic/Inorganic Chromium-Free Co-Passivation Treatments for Galvanized Steel ». Advanced Materials Research 785-786 (septembre 2013) : 881–86. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.881.

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The corrosion resistance of chromium-free passivation film with single chromate-free passivation solution to deal with galvanized steel still has a gap compared to chromate passivation. In this experiment, the passivation solution consisting of the inorganic salt as corrosion inhibitor, silane as sealer, water-based epoxy resin and additives which formed a layer of inorganic and organic composite passivation film on galvanized steel through the synergistic effect between inorganic and organic. The morphology and elements of the passivation film was analyzed by scanning electron microscopy (SEM) and the corrosion resistance of the composite film was tested by neutral salt spray test (NSS), lead acetate spot test (ASS), tafel polarization curves and AC impedance spectroscopy (EIS). The results show that the composite film has a good adhesion and an excellent corrosion resistance, the corrosion area is only 3% after 72h NSS.

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ONO, BUN-ICHIRO, NAOKO ANDOU, MANLI WENG et KEZONG TONG. « Effect of cysteine on chromate resistance in the yeast Saccharomyces cerevisiae. » CHEMICAL & ; PHARMACEUTICAL BULLETIN 34, n^o 1 (1986) : 229–34. http://dx.doi.org/10.1248/cpb.34.229.

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Aguilar-Barajas, Esther, Elyse Paluscio, Carlos Cervantes et Christopher Rensing. « Expression of chromate resistance genes fromShewanellasp. strain ANA-3 inEscherichia coli ». FEMS Microbiology Letters 285, n^o 1 (août 2008) : 97–100. http://dx.doi.org/10.1111/j.1574-6968.2008.01220.x.

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Caballero-Flores, Gustavo G., Yaned M. Acosta-Navarrete, Martha I. Ramírez-Díaz, Jesús Silva-Sánchez et Carlos Cervantes. « Chromate-resistance genes in plasmids from antibiotic-resistant nosocomial enterobacterial isolates ». FEMS Microbiology Letters 327, n^o 2 (16 décembre 2011) : 148–54. http://dx.doi.org/10.1111/j.1574-6968.2011.02473.x.

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Miranda, Alma T., Marcela V. González, Gabriela González, Eréndira Vargas, Jesús Campos-García et Carlos Cervantes. « Involvement of DNA helicases in chromate resistance by Pseudomonas aeruginosa PAO1 ». Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 578, n^o 1-2 (15 octobre 2005) : 202–9. http://dx.doi.org/10.1016/j.mrfmmm.2005.05.018.

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Juhnke, Susanne, Nicola Peitzsch, Nicole H�bener, Cornelia Gro�e et Dietrich H. Nies. « New genes involved in chromate resistance in Ralstonia metallidurans strain CH34 ». Archives of Microbiology 181, n^o 5 (1 mai 2004) : 390. http://dx.doi.org/10.1007/s00203-004-0665-5.

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Viti, Carlo, Francesca Decorosi, Annalisa Mini, Enrico Tatti et Luciana Giovannetti. « Involvement of the oscA gene in the sulphur starvation response and in Cr(VI) resistance in Pseudomonas corrugata 28 ». Microbiology 155, n^o 1 (1 janvier 2009) : 95–105. http://dx.doi.org/10.1099/mic.0.021873-0.

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Pseudomonas corrugata 28 is a Cr(VI)-hyper-resistant bacterium. A Cr(VI)-sensitive mutant was obtained by insertional mutagenesis using EZ-Tn5 <R6Kγori/KAN-2>Tnp. The mutant strain was impaired in a gene, here named oscA (organosulphur compounds), which encoded a hypothetical small protein of unknown function. The gene was located upstream of a gene cluster that encodes the components of the sulphate ABC transporter, and it formed a transcriptional unit with sbp, which encoded the periplasmic binding protein of the transporter. The oscA–sbp transcriptional unit was strongly and quickly overexpressed after chromate exposure, suggesting the involvement of oscA in chromate resistance, which was further confirmed by means of a complementation experiment. Phenotype MicroArray (PM) analysis made it possible to assay 1536 phenotypes and also indicated that the oscA gene was involved in the utilization of organosulphur compounds as a sole source of sulphur. This is believed to be the first evidence that oscA plays a role in activating a sulphur starvation response, which is required to cope with oxidative stress induced by chromate.

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Chung, W. S., W. Y. Yoon et Kwang Jin Kim. « Corrosion Characteristics of Surface-Modified DET Magnesium Powders ». Materials Science Forum 449-452 (mars 2004) : 369–72. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.369.

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Magnesium powders having inactive surface layer have been processed easily and intentionally by DET under fluoride, chromate, and bromide salt. The modified surfaces play an important role in preventing contact with active environments to improve corrosion resistance of Magnesium powders; the image of the surface modified powders was observed using SEM. The composition distribution and characteristics was determined and analyzed by using XRD, XPS, and EIS. Compared with bare Magnesium, the Magnesium having chromate modified surface layer showed a more passive behavior such as smaller current density and nobler potential in 4wt% NaCl solution.

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Fernández, Pablo M., María M. Martorell, Julia I. Fariña et Lucia I. C. Figueroa. « Removal Efficiency of Cr6+by IndigenousPichiasp. Isolated from Textile Factory Effluent ». Scientific World Journal 2012 (2012) : 1–6. http://dx.doi.org/10.1100/2012/708213.

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Resistance of the indigenous strainsP. jadiniiM9 andP. anomalaM10, to high Cr6+concentrations and their ability to reduce chromium in culture medium was studied. The isolates were able to tolerate chromium concentrations up to 104 μg mL−1. Growth and reduction of Cr6+were dependent on incubation temperature, agitation, Cr6+concentration, and pH. Thus, in both studied strains the chromium removal was increased at 30°C with agitation. The optimum pH was different, with values of pH 3.0 and pH 7.0 in the case ofP. anomalaM10 and pH 7.0 usingP. jadiniiM9. Chromate reduction occurred both in intact cells (grown in culture medium) as well as in cell-free extracts. Chromate reductase activity could be related to cytosolic or membrane-associated proteins. The presence of a chromate reductase activity points out a possible role of an enzyme in Cr6+reduction.

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SUDA, Arata, Jun KAWAGUCHI et Takao OGINO. « Effects of Silica Addition on Corrosion Resistance of Dry-in-place Chromate. » Journal of the Surface Finishing Society of Japan 46, n^o 5 (1995) : 437–41. http://dx.doi.org/10.4139/sfj.46.437.

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Dhakephalkar, P. K., J. V. Bhide et K. M. Paknikar. « Plasmid mediated chromate resistance and reduction in Pseudomonas mendocina MCM B-180 ». Biotechnology Letters 18, n^o 10 (octobre 1996) : 1119–22. http://dx.doi.org/10.1007/bf00128577.

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Zhou, Wan Qiu, Da Yong Shan, En Hou Han et Wei Ke. « Phosphate Conversion Coating on Diecast AZ91D and Its Corrosion Resistance ». Materials Science Forum 488-489 (juillet 2005) : 819–22. http://dx.doi.org/10.4028/www.scientific.net/msf.488-489.819.

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A phosphate conversion coating was deposited on diecast AZ91D magnesium alloys, the film was a complex phosphate containing Mg and Al,which showed amorphous structure. Corrosion resistance of conversion coating in 3.5%NaCl was investigated by polarization curve. It was showed that the anodic branch of polarization curve for the phosphate conversion coating presented typical passivation characteristic. Immersion test results showed that the corrosion rate of phosphate conversion coating was less than that of chromate Dow7 film.

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Verner, Petr, Vlastimil Chrást, Karel Krahula, Martin Zmrzlý, Marian Čerňanský, Jana Houdková et Vladimír Vorlíček. « Chromate alternatives in zinc galvanized steel surface treatment ». Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 54, n^o 1 (2006) : 135–44. http://dx.doi.org/10.11118/actaun200654010135.

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Surface treatment of zinc galvanized steel is carried out usually using chromate based baths. These baths are used for improvement of the corrosion resistance and enhancement of the chemical adhesion of organic coatings. Anticorrosive effects of the chromium conversion coatings were not completely exceeded yet by another kind of passivation. Toxicity of CrVI is a basic problem of chromate conversion coats. This paper presents the main results and conclusions of experimental study on zinc conversion layers based on vanadates, using a good CrVI bath as reference. Anticorrosive mechanisms were compared by the corrosion tests in saline cabinet. Inhibition effects were characterized by scanning electron microscopy, by X-ray dispersive spectrometry (EDS) associated X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

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Moon, Kyung Man, et Myung Hoon Lee. « Evaluation on the Corrosion Resistance Improvement by Dipping to Inhibitor Solution of Galvanizing Steel ». Applied Mechanics and Materials 117-119 (octobre 2011) : 1365–69. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.1365.

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Galvanizing method is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other fields etc.. However, galvanized structures inevitably may be corroded rapidly with increasing exposed time because the rate of environmental contamination is accelerating due to the rapid development of industrial society. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, three types of the test specimens, that is, pure galvanizing, galvalume and chromate treated steels were immersed at inhibitor solution. And the effect of inhibitor for their corrosion resistance improvement was comparatively investigated with an electrochemical method. Corrosion current density of the original galvanizing and galvalume steel exhibited the highest and lowest value respectively in seawater. However, the corrosion resistance of these samples was considerably improved by dipped to a inhibitor solution(H3PO4+ Zn(NO3)2+Q). In particular, the galvanizing steel which dipped to the inhibitor solution exhibited the lowest corrosion current density due to the best effect of corrosion resistance improvement compared to other test specimens.

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Shin, Dong-Jun, Yu-Kyoung Kim, Jeong-Mo Yoon et Il-Song Park. « Discoloration Resistance of Electrolytic Copper Foil Following 1,2,3-Benzotriazole Surface Treatment with Sodium Molybdate ». Coatings 8, n^o 12 (26 novembre 2018) : 427. http://dx.doi.org/10.3390/coatings8120427.

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The copper which an important component in the electronics industry, can suffer from discoloration and corrosion. The electrolytic copper foil was treated by 1,2,3-benzo-triazole (BTA) for an environmentally friendly non-chromate surface treatment. It was designed to prevent discoloration and improve corrosion resistance, consisted of BTA and inorganic sodium molybdate (Na2MoO4). Also the ratio of the constituent compounds and the deposition time were varied. Electrochemical corrosion of the Cu-BTA was evaluated using potentiodynamic polarization. Discoloration was analyzed after humidity and heat resistance conditioning. Surface characteristics were evaluated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Increasing corrosion potential and decreasing current density were observed with increasing Na2MoO4 content. A denser protective coating formed as the deposition time increased. Although chromate treatment under severe humidity (80% humidity, 80 °C, 100 h) provided the highest humidity resistance, surface treatment with Na2MoO4 had better heat discoloration inhibition under severe heat-resistant conditions (180 °C, 10 min). When BTA reacts with Cu to form the Cu-BTA-type insoluble protective film, Na2MoO4 accelerates the film formation without being itself adsorbed onto the film. Therefore, the addition of Na2MoO4 increased anticorrosive efficiency through direct/indirect action.

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Becker, Markus. « Chromate-free chemical conversion coatings for aluminum alloys ». Corrosion Reviews 37, n^o 4 (27 août 2019) : 321–42. http://dx.doi.org/10.1515/corrrev-2019-0032.

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AbstractCorrosion of metallic components represents a major issue in the aeronautical sector, giving rise to safety concerns and significant financial damages. Conversion coatings (CC) based on hexavalent chromium provide exceptional corrosion protection at relatively low cost. However, environmental issues and health concerns raised a growing interest in the development of alternative technologies. These must not only be cost effective and environmentally friendly but also provide corrosion resistance and adhesion performance comparable to Cr6+-based CCs. Simultaneously fulfilling all of these criteria is a difficult challenge, and an industrial application has so far only been achieved by a small number of systems. This review critically summarizes the recent scientific literature and patents for chromate-free CCs on aluminum alloys and tries to assess their potential regarding the highly demanding aerospace requirements. The bath composition and coating characteristics of the trivalent chromium process, rare earth chemical conversion coatings, transition metal oxyanion additives, Zr/Ti-based chemical conversion coatings, sol-gel coatings, and smart coatings providing stimulus-related inhibitor release are discussed. The advantages and disadvantages of the alternative technologies with regard to their practical implementation are debated, as the aeronautics industry is confronted with the necessity to move away from chromates in the near term.

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Guo, Qun, Xiaozhen Li, Nan Lin et Junzhe Liu. « Influence of Rust Inhibitors on the Microstructure of a Steel Passive Film in Chloride Concrete ». Coatings 12, n^o 5 (18 mai 2022) : 692. http://dx.doi.org/10.3390/coatings12050692.

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To compare the corrosion inhibition behaviors of rust inhibitors with different mechanisms on steel bars, the rust resistance effect of sodium molybdate (Na2MoO4), sodium chromate (Na2CrO4), benzotriazole (BTA), N-N dimethyl ethanolamine, sodium molybdate (Na2MoO4) + benzotriazole (BTA), and sodium chromate (Na2CrO4) + benzotriazole (BTA) on steel bars in a simulated chloride concrete pore solution was studied. The rust resistance effects of different types of rust inhibitors were assessed by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different types of rust inhibitors on the film formation characteristics of a passive film on a steel bar surface were expounded. The results show that: When sodium molybdate (Na2MoO4) and benzotriazole (BTA) acted together, the impedance value and the capacitive reactance arc radius were the largest, and the density of the passive film and the inhibition efficiency were the highest. The composition of the passive film was primarily composed of iron compounds, and it also contained oxide and adsorption films that were formed on the steel bar surface by the rust inhibitors. The rust resistance effect was proportional to the compactness of the passive film.

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Lufeng, Pang, Zhang Xiao-Lin, Zhang Sheng-Lin, Yao Yu et Li Wei-Wei. « Effect of cerium chloride on corrosion resistance and adhesion of chromate conversion coatings ». Metal Finishing 109, n^o 1-2 (janvier 2011) : 20–25. http://dx.doi.org/10.1016/s0026-0576(11)80007-3.

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Matsuda, T., K. Tsuchimoto, A. Matsuzaki, K. Croes et V. J. Gelling. « Development of chromate-free coated steel sheet with high corrosion resistance and conductivity ». Transactions of the IMF 94, n^o 5 (2 septembre 2016) : 231–35. http://dx.doi.org/10.1080/00202967.2016.1210882.

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Bai, Li Qun, Di Li, Min Guo et Jing Xin. « Rare Earth Conversion Coating of Magnesium Alloy AZ91D ». Materials Science Forum 546-549 (mai 2007) : 555–58. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.555.

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Rare earth chemical conversion coating of Mg alloys was studied. Corrosion and electrochemical behavior in chloride environment were investigated with tests of evolution of hydrogen and electrochemical measurements. The surface morphologies and composition of rare earth conversion coating were studied through SEM, EDAX and XPS. The results showed that rare earth conversion coatings could improve corrosion resistance and their corrosion resistance was comparable with that of chromate coatings (HB/Z5078278). This result was further proved by Polarization and EIS.

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Dos Santos, Wagner Izaltino Alves, Isolda Costa et Célia Regina Tomachuk. « Hydrothermal Surface Treatments with Cerium and Glycol Molecules on the AA 2024-T3 Clad Alloy ». Key Engineering Materials 710 (septembre 2016) : 216–21. http://dx.doi.org/10.4028/www.scientific.net/kem.710.216.

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New treatments for replacement of chromate require lower toxicity and corrosion protection. This study aims to investigate the influence of the combination of a Ce conversion coating (CCCe) with glycol molecules on the corrosion resistance of the AA2024-T3 clad (AA1230). The corrosion resistance of surface treated and untreated samples was evaluated by electrochemical techniques (electrochemical impedance spectroscopy, polarization tests and open circuit potential). These tests were complemented by salt spray tests to accelerate the corrosive effects of weathering. The surfaces were analyzed after corrosion tests by scanning electron microscopy with X-ray energy dispersive detector (SEM - EDX). The results of the CCCe samples in combination with glycol were compared with that of the surface with chromate layer and the results showed that the CCCe treatment is a candidate for replacement of chromating with the advantage that it does not generate toxic residues. The self-healing capacity of the new treatment tested was indicated by the increased formation of corrosion products deposition on top of Fe rich intermetallis in the AA1230 clad with time of exposure to the electrolyte.

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Zhong, Lei, Yang Yu, Wei Cai, Xinxin Geng et Qin Zhong. « Structure–activity relationship of Cr/Ti-PILC catalysts using a pre-modification method for NO oxidation and their surface species study ». Physical Chemistry Chemical Physics 17, n^o 22 (2015) : 15036–45. http://dx.doi.org/10.1039/c5cp00896d.

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Two Cr(vi) species are generated via pre-modification, which play the different roles in the catalytic reaction. That is, oxide state CrO₃ is beneficial to form the redox reaction with Cr₂O₃, and chromate with anionic form is adverse to accumulate SO₂ to improve their resistance.

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Liu, Xuan, Gaofeng Wu, Yanli Zhang, Dan Wu, Xiangkai Li et Pu Liu. « Chromate Reductase YieF from Escherichia coli Enhances Hexavalent Chromium Resistance of Human HepG2 Cells ». International Journal of Molecular Sciences 16, n^o 12 (26 mai 2015) : 11892–902. http://dx.doi.org/10.3390/ijms160611892.

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Wanotayan, Thanyalux, Yuttanant Boonyongmaneerat, Joongjai Panpranot, Eiji Tada et Atsushi Nishikata. « Electrochemical Evaluation of Corrosion Resistance of Trivalent Chromate Conversion Coatings with Different Organic Additives ». ISIJ International 58, n^o 7 (15 juillet 2018) : 1316–23. http://dx.doi.org/10.2355/isijinternational.isijint-2018-044.

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Mondaca, González et Zaror. « Isolation, characterization and expression of a plasmid encoding chromate resistance in Pseudomonas putida KT2441 ». Letters in Applied Microbiology 26, n^o 5 (mai 1998) : 367–71. http://dx.doi.org/10.1046/j.1472-765x.1998.00349.x.

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Nies, A., D. H. Nies et S. Silver. « Nucleotide sequence and expression of a plasmid-encoded chromate resistance determinant from Alcaligenes eutrophus. » Journal of Biological Chemistry 265, n^o 10 (avril 1990) : 5648–53. http://dx.doi.org/10.1016/s0021-9258(19)39411-6.

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