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  • The Effect of Cold-Rolling on the Microstructure and Corrosion Behaviour of 316L Alloy in FLiNaK Molten Salt
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    M. Maric, O. Muránsky, I. Karatchevtseva, T. Ungár, J. Hester, A. Studer, N. Scales, G. Ribárik, S. Primig, M.R. Hill

    The effect of cold-rolling on the microstructure and molten salt corrosion behaviour of 316 L alloy was investigated. Corrosion tests were performed in FLiNaK salt at 600 °C for 300 h. The present results indicate that cold-rolling leads to enhanced corrosion in molten salt despite its beneficial effect on the alloys mechanical properties. It is shown that the corrosion resistance of cold-rolled 316 L alloy is largely governed by the presence of high-angle grain boundaries (HAGBs) and geometrically-necessary dislocations (GNDs). Exacerbated corrosion is thus directly related to the increased prevalence of grain boundaries and dislocations within the microstructure.

    更新日期:2018-07-18
  • Rearrangement of oxide scale on Ni-11Fe-10Cu alloy under anodic polarization in molten Na2CO3-K2CO3
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Cheng Xinhua, Yin Huayi, Wang Dihua

    The effect of anodic polarization on a pre-formed oxide scale of Ni-11Fe-10Cu alloy was investigated in Na2CO3-K2CO3 melt at 750 °C. The pre-formed oxide scale rearranged under anodic polarization and enabled the alloy as an inert anode for oxygen evolution. The anodic polarization has a positive effect on repairing defects in the original oxide scale, i.e., repair-enhancement effect, which can enhance the protectivity of an alloy substrate and eliminate further corrosion and oxidation. This study demonstrates an effective way to prepare a protective oxide scale, and reveals the rearrangement of pre-formed oxide scale under anodic polarization.

    更新日期:2018-07-18
  • Unravelling the Mechanisms of Corrosion Inhibition of Iron by Henna Extract: A Density Functional Theory Study
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Dharmendr Kumar, Vinay Jain, Beena Rai

    The corrosion inhibition effect of the three main constituents in henna extract: lawsone, gallic acid and α-D-glucose, on the Fe (001) surface was studied using density functional theory. Quantum chemical descriptors as well as the interaction energies predict their corrosion inhibition efficiencies to follow the trend: lawsone > gallic acid > α-D glucose consistent with experiments. Lawsone and gallic acid were found to strongly chemisorb on the surface through formation of O-Fe or C-Fe bonds while the interactions of α-D glucose with the surface are rather weak as steric effects preclude ring C and O interactions with surface Fe-atoms.

    更新日期:2018-07-18
  • Atmospheric Chloride-Induced Stress Corrosion Cracking of Laser Engraved Type 316L Stainless Steel
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Benjamin Krawczyk, Paul Cook, Jeff Hobbs, Dirk L. Engelberg

    The influence of aqua blasting and laser engraving on the atmospheric chloride-induced stress corrosion cracking (AISCC) resistance of type 316 L stainless steel has been elucidated by using MgCl2-laden droplet deposits as the test medium. Aqua blasted surfaces showed no evidence of AISCC. Laser engraving resulted in tensile residual stresses, and led to AISCC within two weeks of exposure, with crack growth rates similar to U-bend samples. Introducing compressive residual stresses via peening inhibited crack nucleation, whereas oxide layer removal of engraved surfaces had no effect on AISCC. Strategies to reduce the likelihood of AISCC of laser engraved components are discussed.

    更新日期:2018-07-18
  • Chloride-induced corrosion behavior of cold-drawn pearlitic steel wires
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Song Xiang, Yue He, Wei Shi, Xuanming Ji, Yuanbiao Tan, Jianmin Liu, Ronald G. Ballinger

    The chloride induced corrosion behavior of cold drawn pearlitic steel wires was systematically investigated using electrochemical measurements, namely, electrochemical impedance spectroscopy, and local electrochemical impedance spectroscopy for micro-areas. A 0.05 mol/L NaCl solution mixed with borate buffer solution (pH = 8.45) was used. The results suggest that the corrosion resistance of cold-drawn pearlitic steel decreases with increasing strain to 0.8, but increases with strain up to a value of 1.6. Microstructure evolution was characterized by electron back scatter diffraction in combination with scanning electron microscopy and transmission electron microscopy. Atom probe tomography was used to quantify the cementite decomposition. The quantitation of microstructural parameters with strain suggests that the evolution of defect structure markedly increases the corrosion susceptibility of pearlite for strain up to 0.8. In the case of strain 1.6, refinement of the lamellar structure and cementite decomposition can reduce the volume fraction of cementite that acts as the cathode per corrosion unit (a pearlite/cementite “cell”), giving rise to an increase in the corrosion resistance.

    更新日期:2018-07-18
  • Effects of Al2O3 diffusion barrier layer (including Y-containing small oxide precipitates) and nanostructured YSZ top coat on the oxidation behavior of HVOF NiCoCrAlTaY/APS YSZ coatings at 1100 °C
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Mohammadreza Daroonparvar, Muhamad Azizi Mat Yajid, Charls M. Kay, Hamidreza Bakhsheshi-Rad, Rajeev Kumar Gupta, Noordin Mohd Yusof, Hamidreza Ghandvar, Azrina Arshad, Intan Syaqirah Mohd Zulkifli

    In this research, the effects of thin Al2O3 diffusion barrier layer (including Y-containing small oxide precipitates) and nanostructured YSZ top coat on the high temperature oxidation behavior of HVOF NiCoCrAlTaY/APS YSZ coatings were examined by using isothermal oxidation tests at 1100 °C. Nanostructured YSZ top coat could slightly reduce the double layered TGO growth rate and weight gain of thermal barrier coating systems. However, Al2O3 diffusion barrier layer (consisting of Y-containing small oxide precipitates) could substantially decline the oxidation rate and Ta movement (Ta-enriched oxides formation) in the NiCoCrAlTaY/Al2O3/nanostructured YSZ coating at 1100 °C.

    更新日期:2018-07-18
  • ToF-SIMS study of oxide films thermally grown on nickel-base alloys
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Xiaocui Wu, Svetlana Voyshnis, Antoine Seyeux, Yuriy Chumlyakov, Philippe Marcus

    The oxidation behaviours of polycrystalline and monocrystalline Ni-base alloys (Ni-16Cr-8Fe (wt%)) were investigated in situ by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The oxide layer formed is duplex: an inner chromium-rich layer and an outer layer which is rich in nickel and iron. Time evolution of the composition of inner layer from pure Cr2O3 towards spinel (NiCr2O4) was observed. The oxidation kinetics was accelerated by alloy grain boundaries, which can favour the diffusion of chromium. Both the parabolic and volatilization constants increased with increasing temperature, with kp varying from 1.9×10-3 to 1.6×10-2 nm2.s-1, and kv from 1.0×10-3 to 2.9×10-3 nm.s-1.

    更新日期:2018-07-18
  • Temporal Evolution of Sweet Oilfield Corrosion Scale: Phases, Morphologies, Habits, and Protection
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Gaurav R. Joshi, Karyn Cooper, Xiangli Zhong, Anthony B. Cook, Ehsan A. Ahmad, Nicholas M. Harrison, Dirk L. Engelberg, Robert Lindsay

    Electrochemical measurements and substrate analysis have been employed to study the corrosion of iron in sweet solution (pH = 6.8, T = 80 °C) over a period of 288 h. Correlated with decreasing corrosion rate, diffraction, microscopy, and spectroscopy data reveal the evolution of adhered sweet corrosion scale. Initially, it is comprised of two phases, siderite and chukanovite, with the latter affording little substrate protection. Subsequently, as the scale becomes highly protective, siderite is the sole component. Notably, siderite crystals are concluded to display a somewhat unexpected habit, which may be a trigger for local breakdown of protective sweet scales.

    更新日期:2018-07-18
  • MONTMORILLONITE AS CORROSION PROTECTIVE PIGMENT
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Aldavilma C. Lima, Lívia M. Jou, Oswaldo E. Barcia, Isabel C.P. Margarit-Mattos

    Different types of montmorilonites (MMTs) were studied for a survey of properties which may contribute for corrosion control, while they are employed as pigments in corrosion protective organic coatings. Experimental methodology involves epoxy novolac paints specially formulated with iron oxide plus 1 or 5 wt.% MMTs, long term corrosion tests, gravimetric tests, titrations of MMTs filtrates and suspensions. The emphasis in literature is that MMTs improve barrier properties. Nevertheless, results revealed that MMTs are not inert pigments. They have two important properties hardly considered: active corrosion inhibition and control of H+ permeation which depend on MMTs affinity by water.

    更新日期:2018-07-18
  • Investigation on Machining Induced Surface and Subsurface Modifications on the Stress Corrosion Crack Growth Behaviour of Super Duplex Stainless Steel
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    J. Rajaguru, N. Arunachalam

    After stress corrosion crack testing in a MgCl2 environment, turned surface of super duplex stainless steel showed four types of cracks. The residual stress and surface defects such as feed marks and long grooves generated after machining played a significant role in the direction and orientation of these cracks. The generated cluster of cracks acted as a precursor to the formation of pits. The biaxial tensile stress in the surface promoted successive branching of cracks, which led to high crack density. The subsurface results showed that cracks passing perpendicular to feed marks found more detrimental than the other types.

    更新日期:2018-07-18
  • Effects of normal load on fretting corrosion fatigue of Alloy 690 in 285 °C pure water
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Jiapeng Liao, Jibo Tan, Xinqiang Wu, Lichen Tang, Hao Qian, Yongcheng Xie

    Fretting corrosion fatigue behaviour of Alloy 690 was investigated in 285 °C pure water under different normal loads. With increasing the normal load applied, the fatigue life decreased, more severe surface damage and subsurface deformation were observed. The effects of normal loads on crack characteristics on the longitudinal sections across the fretting fatigue scars and corrosion fatigue fractures were examined. Possible influence of the normal loads on initiation and propagation mechanisms of the fretting corrosion fatigue cracks of Alloy 690 in high-temperature pure water are discussed.

    更新日期:2018-07-18
  • Influence of the microstructure on the corrosion behaviour of 2024 aluminium alloy coated with a trivalent chromium conversion layer
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    R. Saillard, B. Viguier, G. Odemer, A. Pugliara, B. Fori, C. Blanc

    The influence of 2024 aluminium alloy microstructure on the protective properties of trivalent chromium process (TCP) coatings was studied: samples aged at 190 °C were analysed by comparison to a T3 state. The surface Cu coverage after deoxidation was higher for long-aged samples because nanometer scale Cu-rich precipitates formed during ageing behaved as distinct electrochemical entities and contributed to the formation of copper deposits. The growth mechanisms and kinetics of TCP coatings were directly related to the surface Cu coverage: thicker but more defective TCP coatings formed on long-aged samples leading to the lowest anti-corrosion properties.

    更新日期:2018-07-18
  • High Temperature Oxidation Behavior of Ferritic Stainless Steel Containing W and Ce
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-17
    Liangliang Wei, Jiahao Zheng, Liqing Chen, Raja Devesh Kumar Misra

    The oxidation behavior of a ferritic stainless steel alloyed with elements, W and Ce, was studied at 950―1100 °C for up to 100 h. The oxide film was compact and uniform on the addition of Ce, and the number of defects at the oxide/metal interface was significantly decreased such that it exhibited good adhesion. The addition of Ce or combination of Ce and W reduced the number of dissolved Laves phase (Fe,Cr,Si)2(Nb,Mo) at 1000―1050 °C, which precipitated within the grains or at the grain boundaries. The inward growth of oxide film was effectively hindered by Laves phase.

    更新日期:2018-07-18
  • High temperature oxidation of IN 718 manufactured by Laser Beam Melting and Electron Beam Melting: Effect of surface topography
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-10
    Tom Sanviemvongsak, Daniel Monceau, Bruno Macquaire

    The oxidation behaviour of IN 718 alloys produced by laser beam melting and electron beam melting was compared to that of the wrought alloy at 850 °C in laboratory air. Oxide scales of all alloys were similar in nature and morphology with small differences due to powder particles sintered on the surface of additive manufacturing parts. Nevertheless, major differences in surface topography were noticed, these could affect surface area estimations and consequentlymass gain estimations. A quantitative correlation was determined between apparent parabolic rate constant and surface area.

    更新日期:2018-07-12
  • The role of surface deformation in the oxidation response of Type 304 SS in high temperature deaerated water
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-05
    K.B. Fisher, B.D. Miller, E.C. Johns, E.A. Marquis

    The oxide products found on austenitic stainless steels after high temperature exposures in nuclear reactor environments are well documented, but the mechanisms for the oxide formation are still ambiguous. One issue of practical importance is the role of surface deformation on the oxidation response. To address this question, short high-temperature water exposures were conducted on electropolished and ground surfaces of Type 304 stainless steel. Characterization of the developing oxide scales using transmission electron microscopy and atom probe tomography revealed significantly different responses from the two surface finishes. In the absence of sub-surface deformation, the oxide scale grows as an equilibrium phase of uniform composition with accumulation of Cu to the metal/oxide interface. In the presence of significant sub-surface deformation, a non-equilibrium nanostructured oxide scale develops as a result of selective oxidation along fast diffusion paths.

    更新日期:2018-07-08
  • Morpho-chemical investigations and thermodynamic study of Nb-rich passive nodules grown on AISI 441 oxidized in wet atmosphere
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-06
    Valérie Parry, Wichitra Wongpromrat, Laurence Latu-Romain, Céline Pascal, Walairat Chandra-ambhorn, Somrerk Chandra-ambhorn, Yves Wouters, Alain Galerie

    AISI 441 sheets were oxidized from 4 to 24 h at 800 °C in wet atmosphere. Micrometric oxide nodules containing Ti, Nb, Cr and Mn were observed to form on the passive scale. The internal microstructure of these objects was investigated using STEM-EDX and FIB-SEM tomography. Experimental results reveal a complex microstructure linked with the presence of Si and Nb and their competition for interfacial oxidation. Eventually, the chemical compositions of the nodule and of the oxidation affected zone in the nodule vicinity are discussed in relation with thermodynamic calculations investigating the stability of the different oxides.

    更新日期:2018-07-08
  • A glass-ceramic coating with self-healing capability and high infrared emissivity for carbon/carbon composites
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-07
    Qiang Zhen, Zheng Li, Pengfei Hu, Shaolei Song, Feng Zheng

    Featured with the dense and stability under high temperature, a ZrSiO4-aluminosilicate glass coating for the carbon/carbon composites was designed and prepared via a slurry painting-sintering process. The molten aluminosilicate glass can fill the crevices and cracks to improve the compactness, and play a self-healing role to restrain the propagation of the cracks caused by thermal mismatch under the high temperature. Furthermore, it has high infrared emissivity, which is helpful for cooling of composites to improve the antioxidant capacity. This coating has high antioxidation capability with a mass loss of 23.8 g/m2 for substrates at 1773 K for 20 h.

    更新日期:2018-07-08
  • HARD ANODIZING OF AA2011-T3 Al-Cu-Pb-Bi FREE-CUTTING ALLOY: IMPROVEMENT OF THE PROCESS PARAMETERS
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-07
    Massimiliano Bononi, Roberto Giovanardi

    The free-cutting Al-Cu-Pb-Bi alloy AA2011-T3 has been anodized in a traditional sulphuric bath with the aim of producing hard and uniform oxides of technological interest. H2SO4 concentration, electrolyte temperature, Al3+ concentration and current density have been modified. The effect of each process parameter has been evaluated through Potential-vs-time plot, coating hardness, coating thickness, volumetric expansion-ratio and coating defectiveness. SEM analysis has shown that Bi-based intermetallics are the main responsible for the severe defective state. Higher H2SO4 concentration and higher current density have improved coating hardness and defectiveness, however potentiodynamic polarizations have revealed that they do not enhance corrosion resistance.

    更新日期:2018-07-08
  • In-situ formation of SiC, ZrB2-SiC and ZrB2-SiC-B4C-YAG coatings for high temperature oxidation protection of C/C composites
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-07
    R.V. Krishnarao, Md. Zafir Alam, D.K. Das

    Si3N4, (ZrO2+B4C + Si) and (ZrB2+SiC + B4C + Y2O3+Al2O3) were used as precursors for in-situ formation of SiC, ZrB2-SiC and ZrB2-SiC-B4C-YAG coatings respectively. The oxidation behavior of coated C/C composites was studied by cyclic oxidation in air at temperatures between 1500 °C and 1700 °C. The SiC coating exhibited the lowest weight loss at 1500 °C and 1600 °C. After initial mass loss for two cycles of oxidation at 1500 °C, the ZrB2-SiC coating was found to provide the best protection by the precipitated ZrO2 in SiO2 glass at 1700 °C. The ZrB2-SiC-B4C-YAG coating performed well at 1700 °C with the formation of a complex YAG glass containing ZrB2/ZrO2.

    更新日期:2018-07-08
  • Accelerated oxidation behavior of NbSi2 coating grown on Nb substrate at 600-900 °C
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-07
    Jin-Kook Yoon, Gyeung-Ho Kim

    Isothermal oxidation of NbSi2 coating formed on Nb substrate was investigated in air at 600-900 °C, which exhibited the complex and accelerated kinetics at intermediate temperatures and failed due to either the cracking of the NbSi2 coating or the oxide layer formed. This complex oxidation behavior was governed by the balance between the stress generated by the forming of oxide phases and the subsequent stress relaxation processes. Pesting-induced accelerated oxidation at 700 °C was affected by extrinsic factors such as pre-existing defects in NbSi2 coating. Accelerated oxidation originated from the oxide layer cracking at 750 °C was intrinsic to NbSi2.

    更新日期:2018-07-08
  • Interfacial Corrosion of Copper in Concentrated Chloride Solution and the Formation of Copper Hydroxychloride
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Shengxi Li, Mary T. Teague, Gary L. Doll, Eric J. Schindelholz, Hongbo Cong

    This work aims to investigate the waterline corrosion of pure copper in 4 M NaCl solution. Three distinct regions are identified. Corrosion products formed at the waterline are characterized by micro-Raman spectroscopy, complemented by SEM/EDS, as a function of immersion time. The co-existence of four copper species is explained by thermodynamic equilibrium consideration. The composition of spreading region is determined and compared with the oxide film formation in different pH NaOH solutions. The anodic dissolution of copper exposed to the bulk electrolyte is investigated by electrochemical methods. The pH and potential profiles across three regions are proposed.

    更新日期:2018-07-05
  • Effect of post-weld heat treatment on microstructure evolution and pitting corrosion resistance of electron beam-welded duplex stainless steel
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Zhiqiang Zhang, Hongyang Jing, Lianyong Xu, Yongdian Han, Lei Zhao, Xiaoqing Lv

    The effects of electron beam welding and subsequent post-weld heat treatment at different temperatures on the microstructure evolution and pitting corrosion resistance of duplex stainless steel were investigated. The as-welded joint exhibited poor pitting corrosion resistance, and pitting preferentially occurred at the ferrite grain in the weld. Heat treatment promoted austenite formation, Cr2N dissolution, and eliminated dendritic segregation, consequently improving the corrosion resistance of the welded joint. The optimal solution temperature range was 1050–1110 °C. The austenite in the weld was prone to selective corrosion after heat treatment owing to its lower pitting resistance equivalent number.

    更新日期:2018-07-05
  • In-situ Synchrotron GIXRD Study of Passive Film Evolution on Duplex Stainless Steel in Corrosive Environment
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Cem Örnek, Marie Långberg, Jonas Evertsson, Gary Harlow, Weronica Linpé, Lisa Rullik, Francesco Carlà, Roberto Felici, Eleonora Bettini, Ulf Kivisäkk, Edvin Lundgren, Jinshan Pan

    This paper presents new findings about the passive film formed on super duplex stainless steel in ambient air and corrosive environments, studied by synchrotron grazing-incidence X-ray diffraction (GIXRD). The passive film, formed in air, was seen to be a nano-crystalline mixed-oxide. Electrochemical polarisation to the passive region in aqueous 1 M NaCl at room temperature resulted in an increase of the passive film thickness, de-alloying of Fe, and partial loss of crystallinity. After termination of polarization to the transpassive regime, reformation of the mixed-oxides was observed, showing a thicker, semi-crystalline, and more defective nature (more vacancies) with further new oxides/hydroxides.

    更新日期:2018-07-05
  • Effect of oxygen partial pressure on the semiconducting properties of thermally grown chromia on pure chromium
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Y. Parsa, L. Latu-Romain, Y. Wouters, S. Mathieu, T. Perez, M. Vilasi

    Oxidation of chromium at 800 °C for 30 min at oxygen activity from 5.10-14 atm to 5.10-13 atm have been conducted to grow an insulating chromia. Microstructural and semiconducting properties have been investigated using electron microscopy and photoelectrochemistry. The scales always exhibit a duplex microstructure with equiaxed and columnar grains, as well as a both n-type and insulating semiconduction type. Successive oxidation tests have demonstrated the higher protective nature of this chromia scale compared to the air grown one. Chromia semiconducting properties are finally described vs. oxygen activity in a large range of variation.

    更新日期:2018-07-05
  • YSZ/NiCrAlY interface oxidation of APS thermal barrier coatings
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Yao Hu, Canying Cai, Yanguo Wang, Hongchun Yu, Yichun Zhou, Guangwen Zhou

    The interface oxidation induced microstructural evolution of air plasma spayed (APS) thermal barrier coatings (TBCs) is investigated. As the oxidation progresses, the thermally grown oxide (TGO) formed at the YSZ/NiCrAlY interface develops from a bi-layered structure, to a three-layered structure, then to the four-layered structure of Al2O3, Y3Al5O12 (YAG), NiCr2O4 and NiO, respectively. An oxidation mechanism is proposed to account for the growth of the layered TGO. The YAG formation consumes the underlying alumina layer and facilitates the outward diffusion of Cr and Ni, leading to a detrimental effect on the TBC life.

    更新日期:2018-07-05
  • FIVE-YEAR ATMOSPHERIC CORROSION OF Cu, Cr AND Ni WEATHERING STEELS IN A WIDE RANGE OF ENVIRONMENTS
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    I. Díaz, H. Cano, P. Lopesino, D. de la Fuente, B. Chico, J.A. Jiménez, S.F. Medina, M. Morcillo

    This work considers fourteen weathering steels manufactured by adding Cu, Cr and Ni alloying elements to extra mild steel. The steels were exposed for up to 5 years in different atmospheres. The atmospheric corrosion resistance of the steels was evaluated and the rust layers formed were characterised by X-ray diffraction, optical microscopy and scanning electron microscopy. The addition of Ni, particularly at 3.0 wt%, leads to a notable increase in corrosion resistance. The rusts formed contain lepidocrocite, goethite and spinel phases. X-ray diffraction also detected small amounts of kornelite (industrial atmosphere) and akaganeite (marine atmosphere).

    更新日期:2018-07-05
  • Abiotically or microbially mediated transformations of magnetite by sulphide species: the unforeseen role of nitrate-reducing bacteria
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Marjorie Etique, Alexandre Romaine, Isabelle Bihannic, Renaud Gley, Cédric Carteret, Mustapha Abdelmoula, Christian Ruby, Marc Jeannin, René Sabot, Philippe Refait, Frédéric P.A. Jorand

    In the anoxic conditions of nuclear waste deep geological repository, the main iron corrosion products formed at the surface of the carbon steel overpacks are siderite (FeIICO3) and magnetite (FeIIFeIII2O4) that form a rather protective layer. The originality of this work is the consideration of the bacterial metabolism of nitrate-reducing bacteria (NRB), often overlooked in corrosion processes. Klebsiella mobilis was used as a model of NRB and incubated with ferrous carbonates/magnetite corrosion bilayers under anoxic conditions. As a consequence of a combination of biotic and abiotic processes magnetite was reduced to mackinawite (FeIIS) and subsequently transformed to greigite (FeIIFeIII2S4).

    更新日期:2018-07-05
  • Environmentally assisted degradation of spinodal Copper alloy C72900
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Roy Johnsen, Torstein Lange, Gaute Stenerud, Jim Stian Olsen

    In this work, a spinodal Copper alloy – C72900, was tested to investigate the resistance against environmentally assisted degradation. The material was tested according to ISO 15156-3 Level V in sour H2S solution and to cathodic polarization in simulated seawater with stressed samples. The results showed no indications of hydrogen stress cracking under cathodic polarization in seawater. However, cracks up to 3 mm deep were found on the samples exposed to sour H2S environment. Energy Dispersive Spectroscopy showed severe depletion of copper close to the cracks which is associated with selective corrosion. Stress corrosion cracking was the dominating crack mechanism in the ISO 15156-3 Level V test.

    更新日期:2018-07-05
  • Prediction of Corrosion Fatigue Crack Growth Rate in Alloys. Part I: General Corrosion Fatigue Model for Aero-Space Aluminum Alloys
    Corros. Sci. (IF 4.862) Pub Date : 2018-07-04
    Danyil Kovalov, Balázs Fekete, George R. Engelhardt, Digby D. Macdonald

    In this work, a General Corrosion Fatigue Model (GCFM) was developed for predicting corrosion fatigue crack growth rate (CFCGR) in metals under cyclical loading. The GCFM is based on an equation for the potential drop from the external surface to the crack tip of metals as derived from the principle of differential aeration. Development of the GCFM involves consideration of cyclic loading on the CFCGR and of advection between the in-crack and external environment. We demonstrate the influence of corrosion environment and cyclic loading on the crack growth rate in Al-Li alloys in a 1:1 electrolyte (0.6 M NaCl).

    更新日期:2018-07-05
  • Corrosion behaviour of AZ31 magnesium alloy containing various levels of strontium
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    Alireza Sadeghi, Ehsan Hasanpur, Ahmad Bahmani, Kwang Seon Shin

    The effect of Sr addition on corrosion behaviour of AZ31 was investigated. The corrosion properties were characterized by immersion, electrochemical, scanning Kelvin probe microscopy and microstructural experiments. With increasing Sr concentration, the Vf of Al-Sr precipitates increases. Furthermore, SKPFM results show that Al-Sr and Al-Mn precipitates are cathodic compared to the base Mg matrix. Consequently, more micro-galvanic cells are formed by more precipitates resulting in severe corrosion attack. Corrosion starts at regions close to the precipitates and proceeds through the inter-precipitate region. Nyquist plots indicate that the stability of hydroxide/oxide protective film decreased with increasing Sr concentration.

    更新日期:2018-06-22
  • Studies correlation of surface Volta potential with galvanic corrosion initiation sites in solid-state welded Ti-Cu bimetal using AFM-SKPFM
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    Ehsan Rahimi, Ali Rafsanjani-Abbasi, Amin Imani, Saman Hosseinpour, Ali Davoodi
    更新日期:2018-06-22
  • Self-healing ceria-modified coating for corrosion protection of AZ31 magnesium alloy
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    Lénia M. Calado, Maryna G. Taryba, Maria J. Carmezim, M. Fátima Montemor
    更新日期:2018-06-22
  • Simultaneously improving the corrosion resistance and strength of magnesium via low levels of Zn and Ge additions
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    R.L Liu, Z.R. Zeng, J.R. Scully, G. Williams, N. Birbilis

    Satisfactory corrosion resistance remains an issue in the widespread implementation of magnesium (Mg). The use of alloying to improve mechanical properties of Mg generally accelerates corrosion due to microstructural heterogeneity. However, recent works have revealed that additions of elements serving as ‘cathodic poisons’ such as arsenic (As) and germanium (Ge) can reduce cathodic reaction rates and suppress cathodic activation - imparting corrosion resistance. The effect of Ge was translated into a ternary (and mechanically relevant) Mg-alloy system for the first time, revealing an alloy system with a balance of properties, and low rate of corrosion relative to Mg-alloys to date.

    更新日期:2018-06-22
  • Quasi-in-situ observing the growth of native oxide film on the FeCr15Ni15 austenitic alloy by TEM
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    B. Zhang, X.Y. San, X.X. Wei, B. Wu, S.J. Zheng, Y.T. Zhou, X.H. Shao, Q.Q. Jin, L.X. Yang, E.E. Oguzie, X.L. Ma

    Element Cr imparts non-crystallinity effect on the oxide film on iron. Therefore, in contrast with the oxidation of iron, the oxidation process of Fe-Cr alloys is more complicated. By means of high angle annular dark field scanning transmission electron microscopic (HAADF-STEM) imaging combined with electron-energy loss spectroscopy (EELS) and super-X electron dispersed spectroscopy (Super-X EDS) techniques in an aberration-corrected TEM, we have clarified the evolution in the oxide film formed on an FeCr15Ni15 alloy. The oxide film is identified to be amorphous at the initial oxidation stage, but tends to become crystalline in the inner layer after aging in air.

    更新日期:2018-06-22
  • Corrosion inhibition effects of metal cations on SUS304 in 0.5 M Cl- aqueous solution
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    Saiful Islam, Kyohei Otani, Masatoshi Sakairi

    The corrosion characteristics of SUS304 exposed to 0.5 M Cl- aqueous solution containing different metal cations were studied with immersion tests, surface analysis and electrochemical tests. The mechanism of corrosion with metal cations was clarified by the XPS analysis results together with the hard and soft acid and base (HSAB) concept and the passive films structure. It is supposed that metal cations with large hardness make a layer by chemical bonding with the passive films. The passive films are protected by the metal cation layer from Cl- attack, and consequently corrosion reactions are inhibited.

    更新日期:2018-06-22
  • Corrosion mechanism of Zn-30Sn high-temperature, lead-free solder in neutral NaCl solution
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-22
    Zhenghong Wang, Chuantong Chen, Jianchun Liu, Gong Zhang, Katsuaki Suganuma

    Corrosion mechanism of Zn-30Sn high-temperature, lead-free solder in neutral 0.5 M NaCl solution are investigated by using FE-SEM, XRD, XPS and SIMS. The results confirm that α-Zn phases are corroded preferentially. Moreover, during initial corrosion process, a double-layer structure of ZnO and Zn(OH)2 is formed, providing beneficial barrier effect hindering the penetration of Cl-. However, subsequent morphology transformation weakens barrier effect to Cl- penetration and results in severe corrosion. Mechanism of surface layer breakdown and internal corrosion propagation are further examined, where it is determined that aggressive Cl- plays an important role in the corrosion process of Zn-30Sn solder.

    更新日期:2018-06-22
  • The effect of Sn-VO defect clustering on Zr alloy corrosion
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-20
    B.D.C. Bell, S.T. Murphy, R.W. Grimes, M.R. Wenman

    Density functional theory simulations were used to study Sn defect clusters in the oxide layer of Zr-alloys. Clustering was shown to play a key role in the accommodation of Sn in ZrO2, with the {SnZr:VO}× bound defect cluster dominant at all oxygen partial pressures below 10-20 atm, above which View the MathML source Sn Zr × is preferred. {SnZr:VO}× is predicted to increase the tetragonal phase fraction in the oxide layer, due to the elevated oxygen vacancy concentration. As corrosion progresses, the transition to View the MathML source Sn Zr × , and resultant destabilisation of the tetragonal phase, is proposed as a possible explanation for the early first transition observed in Sn-containing Zr-Nb alloys.

    更新日期:2018-06-22
  • Corrosion and tribocorrosion behaviour of β-type Ti-Nb and Ti-Mo surfaces designed by diffusion treatments for biomedical applications
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-21
    J. Ureña, S. Tsipas, A.M. Pinto, F. Toptan, E. Gordo, A. Jiménez-Morales

    Corrosion and tribocorrosion behaviour of modified Ti surfaces through thermochemical treatments has been studied. Electrochemical Impedance Spectroscopy (EIS) and reciprocating sliding tests using a ball-on-plate tribometer under 1 N load and alumina as counter-material were used to evaluate the influence of Nb and Mo on titanium corrosion and tribocorrosion properties. Ti-Nb and Ti-Mo surfaces exhibited better anticorrosive properties than CP-titanium. Under tribological action the modified Ti surfaces showed similar coefficient of friction and lower tendency to corrosion compared to CP-Ti. Furthermore, Nb diffusion increased the repassivation rate with respect to Ti and Ti-Mo surfaces due to its stable passive film.

    更新日期:2018-06-22
  • Formation of Micro/Nano Pits with High Catalytic Activity on Fe80B20 Amorphous Alloy
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-21
    X.H. Zhang, Y.Q. Zeng, L. Yin, J.Q. Jiang, Y. Pan, R. Li, L. Liu, T. Li, K.C. Chan

    In this work, micro/nano size pits were introduced to the surface of Fe80B20 amorphous ribbons by electrochemical etching treatment. The results show that the size of the pits is more sensitive to the applied etching potential, while the pit homogeneity is time dependent. The etching treatment at -0.30 volt (vs saturated calomel electrode) for three hours in 1 M HCl solution saturated by KCl leads to the formation of numerous pits with an average diameter of 222 nm. The large amount of pits results in higher degradation efficiency on Direct Blue 15 when compared with the as-spun amorphous alloy.

    更新日期:2018-06-22
  • Alloy Design Employing High Cr Concentrations for Mo-free Stainless Steels with Enhanced Corrosion Resistance
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-21
    KiMin Jung, SooHoon Ahn, YoungJun Kim, SeKwon Oh, Won-Hee Ryu, HyukSang Kwon

    In this study, we demonstrate the strategic replacement of Mo with excess Cr in Fe-Cr alloys and report their corrosion resistances. To better understand pitting corrosion, the electrochemical properties of the passive films observed on different alloys (Fe-20Cr-2Mo and Fe-25Cr) were compared. Mo-free Fe-25Cr offered comparable or better pitting corrosion resistance than Fe-20Cr-2Mo during film breakdown, repassivation, and pit propagation stages. We investigated the reason for enhanced stability against pitting corrosion as a result of Mo exclusion in such alloys. Mo accelerated co-dissolution of Fe and Mo itself, consequently enriching Cr on the surface and ultimately promoting onset of passivity.

    更新日期:2018-06-22
  • Durability of Fiber Reinforced Polymer (FRP) in Simulated Seawater Sea Sand Concrete (SWSSC) Environment
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-21
    F. Guo, S. Al-Saadi, R.K. Singh Raman, X.L. Zhao

    This paper presents an experimental investigation on the degradation of carbon/glass/basalt fiber reinforced polymer (i.e., CFRP/BFRP/GFRP) exposed to simulated seawater sea sand concrete environments (SWSSC) at 25, 40 and 60 °C for 6 months. The presence of NaCl in simulated concrete environment was found beneficial for the moisture uptake of CFRP and GFRP. The greater fiber degradation of BFRP was attributed to its high aluminium, iron and magnesium contents on fibers. Further, FRPs showed greater degradation resistance in high performance concrete solutions that have a lower alkaline content. Thus, CFRP exhibited the best durability to simulated SWSSC environments, followed by GFRP and BFRP.

    更新日期:2018-06-22
  • Corrosion behaviour of electrodeposited Zn-Cr alloy coatings
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-19
    V. Chakarova, Tz. Boiadjieva-Scherzer, D. Kovacheva, H. Kronberger, M. Monev

    Electrodeposited Zn-Cr alloy coatings show a high potential in protecting steel from corrosion. Investigations in sulphate solutions by electrochemical and analytical methods demonstrate low corrosion of the coatings in pH 4-12 range. Significant dissolution is observed at pH < 4.0, where the alloys dissolve with a higher rate than Zn. The corrosion performance is related to dissolution of the corrosion protective film and the lower hydrogen overvoltage on the alloys than that on Zn. After corrosion of Zn-10.4%Cr the phase composition retains as the parameter (a) of Γ-(Zn,Cr) phase does not change, whereas the parameter (с) of δ-(Zn,Cr) phase decreases.

    更新日期:2018-06-20
  • An approach to study oxidation-induced stresses in Zr alloys oxidized at high temperature
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-19
    M. Le Saux, T. Guilbert, J.C. Brachet

    A method was elaborated to measure the deformation of Zr alloy samples in-situ, during oxidation at high temperature (above 900 °C typically) and subsequent cooling. In addition, a model was developed to calculate the internal stresses generated within the multiphase and multilayered material oxidized at high temperature. Comparison of simulation and experimental results confirmed the benefit of making measurements in-situ rather than post-facto. It was shown that internal stresses generated during oxidation at high temperature are potentially very different from those reported for lower temperatures, due in particular to amplified diffusion of oxygen within the metal and increased viscoplasticity.

    更新日期:2018-06-19
  • Investigation of Precipitation Kinetics of FeCO3 by EQCM
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-18
    Ma Zheng, Yang Yang, Brown Bruce, Nesic Srdjan, Singer Marc

    Iron carbonate (FeCO3) is the most common corrosion product in aqueous CO2 corrosion of mild steel. When it forms, the FeCO3 corrosion product layer may be protective, by serving as a diffusion barrier and by affecting the rate of electrochemical reactions at the surface. In the present study, an Electrochemical Quartz Crystal Microbalance (EQCM) was used to investigate the kinetics of precipitation of FeCO3 from an aqueous CO2 corrosion environment. EQCM is a technique providing very accurate in-situ measurement of surface mass change, enabling also simultaneous electrochemical measurements. Three different substrates were used to conduct the FeCO3 precipitation experiments: a cathodically polarized gold-coated quartz crystal, a freely corroding iron-coated quartz crystal and a cathodically polarized iron-coated quartz crystal, at varied temperatures (50 – 80 °C). Precipitation rates of FeCO3 obtained by using EQCM were repeatable and consistent across different substrates. The obtained precipitation rates were used to determine the theoretical kinetic constant and the activation energy, which was then compared with those reported in the Sun and Nesic model (2008). Discrepancies between the predicted and experimental values were noticed at lower saturation levels and improvements in the model are proposed.

    更新日期:2018-06-19
  • Corrosion protection properties of inhibitor containing hybrid PEO-epoxy coating on magnesium
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-15
    Junjie Yang, Carsten Blawert, Sviatlana V. Lamaka, Darya Snihirova, Xiaopeng Lu, Shichun Di, Mikhail L. Zheludkevich

    A hybrid PEO-epoxy coating was developed for magnesium. A highly-efficient corrosion inhibitor (3-methysalicylate) was impregnated into the anodized layer, which was sealed by an epoxy layer through dip-coating process. Influence of dip-coating parameters on coating properties was investigated. The corrosion performance was evaluated through general and localized electrochemical techniques. As a result, the epoxy layers registered superior resistance, whereas the anodized layer suppressed corrosion expansion. Longer immersion and triple-dipping favored the production of better sealed epoxy layer. The active protection mechanism was achieved by suppression the re-deposition of detrimental impurity and/or adsorption upon the exposed surface from incorporated inhibitor.

    更新日期:2018-06-15
  • Mechanisms of hot corrosion of pure nickel at 700°C: influence of testing conditions
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-15
    Benjamin Grégoire, Xabier Montero, Mathias C. Galetz, Gilles Bonnet, Fernando Pedraza

    The hot corrosion behaviour of pure nickel was investigated at 700 °C to highlight the influence of testing conditions (composition of the atmosphere and presence or not of a Na2SO4 deposit) on the mechanisms of hot corrosion. The influence of SO2/SO3 inward transport through the porous NiO growing scales was studied by exposing nickel in synthetic air and in synthetic air + 0.5% SO2/SO3 without Na2SO4. The addition of Na2SO4 decreased the pO2 p O 2 and the pSO3 p S O 3 at the sample surface, which promoted the formation of Ni-S liquid solution at the metal/scale interface. A sufficient pSO3 p S O 3 was required to stabilize liquid Na2SO4-NiSO4 solutions and simulate Type-II hot corrosion conditions.

    更新日期:2018-06-15
  • ToF-SIMS and ERDA study of hydrogen and deuterium in nickel-base alloys oxidized in water
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-15
    Xiaocui Wu, Antoine Seyeux, Ian Vickridge, Svetlana Voyshnis, Philippe Marcus

    The depth profiling of hydrogen and deuterium in polycrystalline and monocrystalline Nickel-base alloys (Ni-16Cr-8Fe, wt%) was performed by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Elastic Recoil Detection Analysis (ERDA) after oxidation in simulated primary medium conditions containing 9 at.% D2O. The use of deuterium isotopic tracer in ToF-SIMS has demonstrated the presence of deuterium in the oxide layer for oxidation times of 300 min and 100 h. The quantities of deuterium were determined by ERDA using a 2 MeV 4He ion beam. Finally, the penetration coefficient α was calculated, and ranged from 0.01 to 0.04.

    更新日期:2018-06-15
  • Clustering of corrosion pit depths for buried cast iron pipes
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-15
    Zohreh Soltani Asadi, Robert E. Melchers

    The exterior surfaces of cast iron pipes buried in clay soils for up to 129 years show clustering of pits of similar depth at progressively greater overall corrosion pit depth. Within experimental accuracy, the pit depth increments are approximately constant over the whole range of pit depth for each soil. They increase with lower soil pH and appear insensitive to other soil properties and to burial period. These new findings are interpreted relative to pitting electrochemical potential and compared with field observations for pitting in marine corrosion of steel. Implications for modelling maximum pit depth development are considered.

    更新日期:2018-06-15
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  • 更新日期:2018-06-15
  • Designing and fabricating of single and double alkyl-chain indazole derivatives self-assembled monolayer for corrosion inhibition of copper
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-13
    Yujie Qiang, Shulei Fu, Shengtao Zhang, Shijin Chen, Xuefeng Zou
    更新日期:2018-06-14
  • Designing the corrosion products of ZnAl15: a new approach to smart corrosion protection coatings?
    Corros. Sci. (IF 4.862) Pub Date : 2017-12-20
    Kirsten Bobzin, Mehmet Öte, Martin Andreas Knoch

    ZnAl coatings are known to provide reliable corrosion protection for low-grade structural steels in most environments. Depending on the coating process, different phase compositions can be observed in such coatings. In case of thermal spraying, the high cooling rates were proven to result in the formation of metastable β-ZnAl for the first time in literature. To assess the influence on the corrosion behaviour, β-ZnAl and α-η-ZnAl samples were produced and corroded in a salt spray test. A pronounced influence of the phase composition on the formation of layered double hydroxides was observed.

    更新日期:2018-06-12
  • High Resolution Characterization of Sulfur-Assisted Degradation in Alloy 800
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-11
    S.Y. Persaud, F. Long, A. Korinek, J.M. Smith

    Environmentally assisted cracking (EAC) initiation tests were carried out by subjecting Alloy 800 tensile specimens to 0.55 mol/kg SO42- solution, pH280°C 3, at 280 °C using slow rise-time cyclic loading and in-situ crack detection. EAC, intergranular corrosion (IGC), and pitting were observed. Transmission electron microscopy analysis revealed Ti- and Cr-rich oxides in cracks, and sulfur incorporated in oxide(s) or as sulfide compound(s). This oxide/sulfide film is likely impaired, producing a slip dissolution-type EAC mechanism. For pitting, only a nano-scale sulfur layer was identified at pit-metal interfaces. This high surface coverage of adsorbed sulfur limited oxide nucleation and accelerated metal dissolution.

    更新日期:2018-06-12
  • Improved corrosion resistance of Mg–8Sn–1Zn–1Al alloy subjected to low-temperature indirect extrusion
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-11
    Soo-Min Baek, Jeong Su Kang, Jong Chan Kim, Beomcheol Kim, Hyung-Joon Shin, Sung Soo Park

    We report that the corrosion resistance of Mg–8Sn–1Zn–1Al alloy is significantly improved by the application of a low-temperature indirect extrusion process utilizing artificial cooling. It was found that the corrosion rates, measured by immersion tests in 0.6 M NaCl solution at 25 °C, are 27.5 and 246.7 mm y-1 for the alloys extruded with and without artificial cooling, respectively. The remarkably improved corrosion resistance is mainly attributed to the reduced nobility of cathodic Al5Fe2 particles, which results in retarded microgalvanic corrosion in the corrosive condition. Metallurgical factors affecting the electrochemical nobility of Al5Fe2 particles are discussed.

    更新日期:2018-06-12
  • Influence of matrix cracking and hybrid fiber reinforcement on the corrosion initiation and propagation behaviors of reinforced concrete
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-08
    Wilson Nguyen, Jacob F. Duncan, Gabriel Jen, Claudia P. Ostertag
    更新日期:2018-06-08
  • New insight on early oxidation stages of austenitic stainless steel from in situ XPS analysis on single-crystalline Fe-18Cr-13Ni
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-07
    Li Ma, Frédéric Wiame, Vincent Maurice, Philippe Marcus

    In situ X-ray photoelectron spectroscopy real-time measurements and angular-dependent high resolution core level analysis were used for the first time to investigate the Cr enrichment and oxide growth mechanisms on a model 304 austenitic stainless steel surface in the very initial stages of oxidation leading to pre-passivation. The oxidation kinetics was followed for increasing oxygen exposure and temperature, revealing an early nucleation regime (for exposure <10 L) leading to the formation of a strongly Cr-enriched Cr3+/Fe3+ mixed layer followed by an oxide growth regime where preferential iron oxidation takes over and mitigate the initial chromium enrichment.

    更新日期:2018-06-07
  • The Role of Corrosion Inhibition in the Mitigation of CaCO3 Scaling on Steel Surface
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-06
    Tianzhen Zhu, Lida Wang, Wen Sun, Meng Wang, Jisheng Tian, Zhengqing Yang, Suilin Wang, Liang Xia, Shaohui He, Yingzheng Zhou, Guichang Liu

    Corrosion-induced CaCO3 scaling is extremely widespread at metal/water interface. However, the anti-scale and anti-corrosion behaviour of existing inhibitors have mostly been investigated separately without considering their interaction. Herein, the roles of corrosion inhibition in mitigating interfacial scaling were evaluated on carbon steel and stainless steel by introducing NaNO2 to enhance their corrosion resistance. Results reveal that corrosion-induced pH increase at micro cathodes dominates the interfacial scaling processes by inducing rapid nucleation. A temperature elevation promotes interfacial scaling mainly through aggravating steel corrosion. Once the micro cathodic processes are inhibited, CaCO3 scaling can be evidently retarded even at elevated temperatures.

    更新日期:2018-06-07
  • Spallation resistance of oxide scales on Alloy 617 enhanced by boron addition
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-05
    Hyeonuk Jeong, Se-Ho Kim, Won Seok Choi, Pyuck-Pa Choi

    We report on the effects of B additions to Alloy 617 on its high-temperature oxidation behavior and on the spallation of oxide scales. Alloy 617 and a B-added derivative (Alloy 617B) were oxidized at 1050 °C in air and comparatively studied. Cr2O3 scales formed on both alloys with a spinel phase and a Ti-rich oxide on top. While both alloys showed similar scale growth kinetics, Alloy 617B showed substantially enhanced resistance to oxide scale spallation. B segregation at Cr2O3 grain boundaries, detected by atom probe tomography, was found to be the reason for the enhanced spallation resistance of Alloy 617B.

    更新日期:2018-06-06
  • Oxidation behaviour of Nb-rich Ni-Cr-Fe alloys: Role and effect of carbides precipitates
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-01
    Y.X. Xu, J.T. Lu, W.Y. Li, X.W. Yang

    Present work aims to find the influence of carbide precipitates on the oxidation behaviour of Nb-rich Ni-Cr-Fe alloys at 1000 °C in air. Three Ni-Cr-Fe alloys, NC-15Fe-1Nb, NC-15Fe-1Nb-0.8C, NC-15Fe-1Nb-0.8C-0.5Ti were designed by alloying with Ti, Nb and C. Results show that the formation of NbC is crucial for the preferential oxidation of Cr. Moreover, either preventing NbC formation or favouring (Ti,Nb)C formation is found detrimental on such a beneficial effect, where the latter has a more intense influence. Roles of the precipitates in oxidation mechanism give new insights into the alloy optimization.

    更新日期:2018-06-01
  • Enhancement of Oxidation Resistance of Zirconium Alloy with Anodic Nanoporous Oxide Layer in High-Temperature Air/Steam Environments
    Corros. Sci. (IF 4.862) Pub Date : 2018-06-01
    Yang Jeong Park, Jung Woo Kim, Ghafar Ali, Sung Oh Cho

    Highly-ordered and hexagonally close-packed nanoporous zirconium oxide layer is formed on the surface of zirconium alloy by anodization, and the anti-oxidation behavior of the zirconium alloy with the nanoporous oxide layer has been investigated. The oxidation experiments were carried out in both air and steam environments at 1000 °C. Interestingly, zirconium alloy with the nanoporous oxide layer exhibits dramatic improvement in the oxidation resistance compared to bare zirconium alloy without the nanoporous oxide layer. Analysis using several characterization tools reveals that large single-crystalline columnar zirconium oxide grains are formed beneath the nanoporous oxide layer and these grains prevent further oxidation.

    更新日期:2018-06-01
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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