LIU Changqing YU Li YU Zhiming JIN Zhujing WU Weitao Corrosion Science Laboratory
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Institute of Corrosion and Protection of Metals
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Academia Sinica
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Shenyang
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China
金属学报(英文版)
The fine rnicrostrueture of the Y-modified ion plated Ti(Y)N coating/substrate steel A3 system has been examined by means of TEM and microdiffraction technique.It was revealed that the interface consists of 3 sublayers,i.e.α-Fe+Y_6Fe_(23),Ti+Y+FeTi and Ti_2N+YN +Ti_xN_y.The thicknesses of them are about 200,50 and 120 nm respectively.The phases in the transition area seem to have certain orientation relations.The mechanism of interface formation has also been discussed.
关键词:
Ti(Y)N coating
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Corrosion Science
The early stages of the evolution of atmospheric corrosion of carbon steels exposed in both a laboratory simulated and a natural atmosphere environment in Shenyang have been observed by in situ scanning electron microscopy. In the case of laboratory cyclic wet-dry tests, even though the chloride content level is very low, filiform corrosion is initiated in the early stage. The filiform corrosion grows in random directions, forming a network of ridges. White nodules nucleate and grow on the ridges during continued corrosion and eventually connect with each other to form the initial corrosion scale. Pits were also found on the surface beneath corrosion products. In the case of a natural atmospheric environment, both filiform corrosion and other localized corrosion, such as pitting and inter-granular attack take place in the initial stage. It is obvious that there is variety of localized corrosion in the initial stage of atmospheric corrosion. (C) 2007 Elsevier Ltd. All rights reserved.
关键词:
steel;atmospheric corrosion;initial stage;localized corrosion;in-situ;iron;electrolyte;thickness
Materials Chemistry and Physics
The corrosion behaviour of CortenA weathering steel has been investigated using a laboratory accelerated test that involved cyclic wet/dry conditions in Qinghai salt lake water diluted 30 times The characteristics of the rust layers on tested samples were observed by SEM and EPMA analyzed by IRS and XRD and studied by polarization and EIS measurements The weight loss was almost linear indicating that the rust layer had no retarding effect on the corrosion process The crystalline components of the rust layers consisted primarily of beta-FeOOH magnetite (Fe(3)O(4)) and gamma-FeOOH As the corrosion proceeded the amount of beta-FeOOH decreased while that of magnetite and gamma-FeOOH increased XRD EDAX and EPMA indicated that the complex corrosion products magnesioferrite (MgFe(2)O(4)) and iowaite (Mg(4)Fe(OH)(8)OCl 4H(2)O) probably existed in the rust layer in which case they will have had an important Influence on the protectiveness of the rust layer The results of electrochemical measurements showed that the rust layer exhibited high reduction reactivity which facilitated the corrosion of weathering steel in the wetting process The large rust capacitance and small rust resistance indicated that the rust layer had a loose and porous structure which provided poor protection (c) 2010 Elsevier B V All rights reserved
关键词:
Elements;Corrosion test;Electrochemical techniques;Electron probe;low-alloy steels;atmospheric corrosion;carbon-steel;electrochemical;impedance;room-temperature;rust layers;iron;mechanism;products;environment
Corrosion
An evaluation was conducted of the corrosion behavior of 8090 aluminum-lithium (Al-Li) alloy (UNS A98090), when aged under various conditions and subjected to corrosion in a solution of 3.5% NaCl + 1% H2O2. Susceptibility to pitting, intergranular corrosion, and exfoliation corrosion was shown to be influenced by heat treatment, which reduced from natural aging, through overaging to peak aging. Materials with peak aging showed low corrosion resistance. The decreased corrosion resistance corresponded to decreased corrosion potential of the alloy. Insoluble constituents were susceptible to corrosion. The corrosion extended along grain boundaries. Al-Li alloys showed mismatched tensile strength and stress corrosion resistance. The growth rate of stress corrosion cracks was large in the peak-aged state. The growth rate was strengthed by overaging, but tensile strength was reduced. That problem was solved by retrogression and reaging processing.
关键词:
aluminum-lithium alloy;corrosion resistance;exfoliation corrosion;intergranular corrosion;retrogression and reaging treatment;stress;corrosion cracking;aluminum-alloy;strength;lithium
Surface & Coatings Technology
Using a halide-activated pack-cementation method but at a temperature (600 degrees C) noticeably lower than normal, an eta-Fe(2)Al(5) coating and two delta-Ni(2)Al(3) coatings with and without dispersions of CeO(2) nanoparticles were developed respectively on a low-carbon steel and the steel pretreated with an electrodeposited film of Ni or Ni-CeO(2). The erosion-corrosion (E-C) performance of the three aluminide coatings during 100 h exposure at similar to 600 degrees C in a coal-firing laboratory-scale fluidized-bed combustor (FBC) was investigated, by mounting the aluminized samples onto a rig which maintained rotation for accelerating the relative impacting speed of flying solid particles (mainly SiO(2) bed materials). The eta-Fe(2)Al(5) and the CeO(2)-free delta-Ni(2)Al(3) coatings experienced an unacceptable recession rate. Compared to the two CeO(2)-free aluminide coatings, the CeO(2)-dispersed delta-Ni(2)Al(3) coating offered profoundly improved E-C resistance, because the latter coating was not only strengthened by the CeO(2) dispersion and grain refinement, it also could grow a more adherent alumina scale. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Erosion-corrosion;CeO(2)-dispersion-strengthening;Aluminizing coating;Grain refinement;Hardening;Reactive element effect;oxidation resistance;reactive elements;alloy-steels;water-vapor;power-plant;nickel;combustion;mechanisms;additions;behavior
Corrosion Science
The corrosion of pure Ni and of binary Ni-Ti alloys containing 5, 10, and 15 wt.% Ti respectively in molten (0.62Li,0.38K)(2)CO3 at 650 degreesC under air has been studied. The corrosion of the single-phase Ni-5Ti alloy was slower than that of pure Ni, forming an external scale composed of NiO and TiO2. The two-phase Ni-10Ti and Ni-15Ti alloys underwent much faster corrosion than pure Ni, producing an external scale containing NiO and TiO2, and a thick internal oxidation zone of titanium mainly involving the intermetallic compound TiNi3 in the original alloys. The rates of growth of the external scales for the Ni-Ti alloys were reduced with the increase of their titanium content, while the internal oxidation was significantly enhanced. The corrosion mechanism of the alloys is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.
关键词:
nickel;Ni-Ti alloys;molten (Li,K)(2)CO3;molten-salts corrosion;carbonate fuel-cells;internal oxidation;base alloys;oxygen;li2co3-k2co3;solubility;diffusion;behavior;nickel
Materials Letters
Corrosion of the reduction vessel induced by molten LiCl-Li2O is an important problem in the lithium reduction technique for the spent nuclear fuel management. This study investigates the corrosion of NiAl-28Cr-5.8Mo-0.2Hf alloy in the molten LiCl-10 wt.%Li2O at 750 degreesC by immersion experiments. The alloy is mainly composed of NiAl(beta) phase and Cr(Mo) phase. The corrosion scale is composed of LiCrO2 and LiAlO2. The NiAl(beta) phase is corroded slowly because of the depletion of Al near the phase boundaries, but the Cr(Mo) phase undergoes fast corrosion, which results in that the corrosion of Cr(Mo) phase is preceded over that of the NiAl(beta) phase in the molten LiCl-10 wt.%Li2O. The corrosion kinetic curve shows a linear pattern, which is mainly attributed to the fast corrosion of Cr(Mo). (C) 2003 Elsevier Science B.V. All rights reserved.
关键词:
NiAl-28Cr-5.8Mo-0.2Hf alloy;LiCl-10 wt.%Li2O;corrosion;carbonate fuel-cell;plated material;composites;iron
