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Progress in Characterization of Metallic Materials Corrosion by Ultraviolet Photoelectron Spectroscopy and X-ray Photoelectron Spectroscopy
In fact, the metallic material corrosion process may intrinsically involve subprocesses such as the exchange of valence electron between metallic atoms and ions in corrosive medium, the formation of oxide scale, the migration of corrosive species through the formed oxide scale, and the interaction b. . .
Journal of Chinese Society for Corrosion and protection, 2016 Vol. 36 (4): 287-294    DOI: 10.11902/1005.4537.2016.096
 
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Current Issue More>>
      30 March 2017, Volume 37 Issue 1 Previous Issue   
    Oxidation Behavior during High Temperature Homo-genization Treatment of Cast Ni-Fe Based Corrosion Resistant 925 Alloy
    Zhan ZHAO,Jingyang LI,Jianxin DONG,Zhihao YAO,Maicang ZHANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 1-8.   DOI: 10.11902/1005.4537.2016.189
    Abstract   HTML   PDF (2004KB)

    The oxidation behavior of the as-cast 925 superalloy were investigated in the temperature range of 1130~1190 ℃ by means of mass change measurement, X-ray diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that after homogenization treatment at 1160 ℃ for 20 h, the formed oxide-scale showed three-layered structure: an internal oxidation layer composed of Al2O3 and TiO2, a continuous and dense middle layer of Cr2O3 and an outmost layer of the spinel oxidation of Cr and Fe. When the homogenization time increased, the layer of Cr2O3 became thinner and the spinel oxides of Cr and Fe begun to break down and the oxidation was aggravated. Taking the oxidation behavior of the alloy during homogenization into account, the appropriate homogenization of 925 superalloy should be conducted at 1160 ℃ for 20 h.

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    Crack Growth Rate of Stress Corrosion Cracking of Inconel 625 in High Temperature Steam
    Naiqiang ZHANG,Guoqiang YUE,Fabin LV,Qi CAO,Mengyuan LI,Hong XU
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 9-15.   DOI: 10.11902/1005.4537.2016.088
    Abstract   HTML   PDF (1038KB)

    Stress corrosion crack growth rate (CGR) tests of nickel-based alloy Inconel 625, as a candidate material for 700 ℃ ultra-supercritical steam turbine, has been completed at 700~750 ℃ in environments of alternating air and water vapor, as well as in steam with 0~8000 μg/L dissolved oxygen. The applied load is constant stress with intensity factor (K) and the crack growth rate is detected online by measuring the direct current potential drop (DCPD). Results show that the CGR in water vapor is greater than in air and which increases with increasing temperature and dissolved oxygen content. The mechanisms concerning the influence of temperature, medium environment and dissolved oxygen content on stress corrosion cracking are discussed.

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    Corrosion Behavior of 316 Stainless Steel in Mixed Molten Nitrate Salts with and without Rare Earth Element
    Ming ZHU,Guyue ZHOU,Huihui ZHANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 16-22.   DOI: 10.11902/1005.4537.2016.150
    Abstract   HTML   PDF (913KB)

    Ternary nitrate salts are widely used as thermal storage medium for solar thermal power generation system, but the corrosion damage of the heat storage pipe caused by the molten nitrate salts is significantly severe. In order to improve the corrosion resistance of the pipeline material, the corrosion behavior of 316 stainless steel in mixed molten nitrate-salts KNO3-NaNO2-NaNO3 without and with addition of 1‰ (mass fraction) and 2‰Y2O3 was comparatively studied by means of electrochemical method and SEM/EDS. The results showed that the addition of Y2O3 can reduce the corrosion rate of stainless steel. The corrosion current density decreased from 9.47 mAcm-2 to 7.13 and 3.73 mAcm-2 respectively with the addition of 1‰ and 2‰Y2O3 and correspondingly, the transfer resistance of 316 stainless steel in mixed molten nitrate salts was enhanced. It can be concluded that the addition of trace of rare earth element is an effective way to improve the corrosion resistance of 316 stainless steel in the mixed molten nitrate salts.

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    Hot Corrosion of T91 Steel in Molten Mixture of KCl+Na2SO4+K2SO4
    Guangming LIU,Kangsheng LIU,Xiaofei MAO,Zhongping WAN,Jianhang HUANG,Mingming YU,Yuankui WANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 23-28.   DOI: 10.11902/1005.4537.2016.168
    Abstract   HTML   PDF (1182KB)

    The hot corrosion behavior of T91 steel in molten salts of 10%KCl+10%K2SO4+80%Na2SO4was studied at 600, 650 and 700 ℃ respectively. The microstructure and composition of the corrosion products were characterized by scanning electron microscope/energy dispersive spectroscope (SEM/EDS) and X-ray diffraction (XRD). Mass loss was observed at various temperatures during the tests, especially disastrous mass loss occurred at 650 and 700 ℃. The main corrosion product was identified as Fe3O4 after corrosion at 600 ℃. However, the corrosion products spalled off seriously during the hot corrosion at 650 and 700 ℃. The residual corrosion products were rich in S, which was the main reason for serious spallation of the corrosion products. Cl existed in the molten salts could react with Cr2O3 to form volatile CrO2Cl2, which accelerated the hot corrosion process.

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    Corrosion Resistance of Alternately Multilayered Coating Ti/TiAlN on Ti-alloy Ti-6Al-4V Beneath a Solid NaCl Film in Atmosphere of Water Vapor and Oxygen at 600 ℃
    Mingming ZHANG,Li XIN,Xueyong DING,Shujiang GENG,Shenglong ZHU,Fuhui WANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 29-35.   DOI: 10.11902/1005.4537.2016.148
    Abstract   HTML   PDF (917KB)

    An alternately multilayered coating Ti/TiAlN and a coating of single layer TiAlN were respectively deposited on Ti- alloy Ti-6Al-4V by arc ion plating. Corrosion resistance of the alloy Ti-6Al-4V with the two coatings covered with a solid NaCl film was comparatively investigated in flowing atmosphere of water vapor and oxygen at 600 oC. The results show that the coating of single layer TiAlN exhibits columnar structure, which may contains some intrinsic defects such as pinholes acting as short-circuit diffusion paths for the inwards migration of corrosive species. On the other hand, the direct connection of the above mentioned short-circuit diffusion paths located in any two nearest neighbour TiN layers may be disturbed due to the intercalation of Ti layers for the Ti/TiAlN multilayer coatings, thus being beneficial to the corrosion resistance of the coating. In fact, the coating of single layer TiN showed clearly characteristics of localized corrosion induced by NaCl in flowing atmosphere of H2O and O2, while the coating of multilayered Ti/TiAlN kept intact. In general, the corrosion resistance of the multilayered Ti/TiAlN coating was much better than that of the single layer TiAlN coating.

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    Hot-gas Corrosion Resistance of La2Ce2O7/8YSZ Duble-ceramic-layered Thermal Barrier Coating
    Xizhong WANG,Jianhao WU,Hui PENG,Hongbo GUO,Shengkai GONG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 36-40.   DOI: 10.11902/1005.4537.2016.175
    Abstract   HTML   PDF (1044KB)

    Double-ceramic-layered (DCL) TBCs of La2Ce2O7(LC)/8YSZ were prepared by electron beam physical vapor deposition (EB-PVD) on Ni-base superalloy. The high temperature stability and corrosion-resistant property of TBCs was investigated in high temperature gas corrosion environment. The results show that no decomposition and phase transformation arises in the TBCs after 100 h exposure at 950 ℃ in the flowing air with aviation kerosene and artificial seawater. The TBCs display good high temperature gas corrosion-resistant property. A continuous and dense oxide scale forms on the bonding coat. No spallation of TBCs occurred after 100 h thermal cycling in the corrosion environment.

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    Optimization of Preparation Process of Solution Precursor Plasma Spraying for SrZrO3 Thermal Barrier Coating
    Xinhui LI,Wen MA,Yichuan YIN,Bole MA,Yu BAI,Ruiling JIA,Hongying DONG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 41-46.   DOI: 10.11902/1005.4537.2016.172
    Abstract   HTML   PDF (841KB)

    SrZrO3 thermal barrier coating was prepared by solution precursor plasma spraying (SPPS). Corresponding to Taguchi method, the relevant processing parameters were optimized in terms of the deposition efficiency, microhardness, microstructure and phase stability of the prepared coatings. The phase constitutes, microstructure and microhardness of the coatings were characterized by XRD, SEM and a microhardness tester, respectively. The experimental results showed that, in the case that the spray distance, feedstock flow rate and atomization pressure are given, the optimized spray parameters were set as follows: arc current, 600 A; argon flow rate, 40 L/min; hydrogen flow rate, 10 L/min. The SrZrO3 coating prepared with the optimized spray parameters had a single-pass coating thickness of 6.0 μm, porosity of 16.3%, and microhardness of 6.8 GPa. The results of phase stability analysis indicated that, the phase transition from t-ZrO2 to m-ZrO2 in the SrZrO3 coating emerged gradually at 1450 ℃ with increasing time, while the SrZrO3 phase did not change.

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    Corrosion Resistance of (Gd0.7Sr0.3)ZrO3.35 Coating against CaO-MgO-Al2O3-SiO2 (CMAS)
    Lili CAI,Wen MA,Xinhui LI,Yichuan YIN,Bole MA,Yu BAI,Jun WANG,Hongying DONG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 47-52.   DOI: 10.11902/1005.4537.2016.171
    Abstract   HTML   PDF (1291KB)

    (Gd0.7Sr0.3)ZrO3.35 coating was prepared on superalloy In718 by air plasma spray (APS). The corrosion behavior of (Gd0.7Sr0.3)ZrO3.35 coated alloy beneath a deposit of 30 mg/cm2 CMAS was examined in air at 1250 ℃for 1, 4, 8 and 12 h, respectively. While the reaction of the powder mixture of (Gd0.7Sr0.3)ZrO3.35 and CMAS was also studied parallel. The phase constitutes and microstructures of the corrosion products were characterized by XRD and SEM, respectively. The results showed that the (Gd0.7Sr0.3)ZrO3.35 coating had better resistance against CMAS corrosion. The corrosion products formed between CMAS and (Gd0.7Sr0.3)ZrO3.35 coating during the corrosion process consists of apatite Ca2Gd8(SiO4)6O2 and c-ZrO2, which can effectively protect the (Gd0.7Sr0.3)ZrO3.35 coating from further attack by CMAS.

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    Corrosion Resistance of Air Plasma Sprayed Thermal Barrier Coating SrZrO3 on Superalloy In718 against CaO-MgO-Al2O3-SiO2 (CMAS)
    Shanrong ZHANG,Hongying DONG,Wen MA,Yichuan YIN,Xinhui LI,Yu BAI,Ruiling JIA
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 53-57.   DOI: 10.11902/1005.4537.2016.170
    Abstract   HTML   PDF (866KB)

    SrZrO3 powders were synthesized by solid-state reaction and then spray granulation. The SrZrO3 coating on superalloy In718 was prepared by air plasma spray (APS). The corrosion behavior of the SrZrO3 coated alloy beneath a thin deposit of CMAS (CaO-MgO-Al2O3-SiO2) was examined in air at 1150 and 1250 oC for 1, 4 and 12 h respectively, while the reaction of powder mixture of SrZrO3 and CMAS was investigated paralell. The corrosion products of SrZrO3 powders and the microstructure of SrZrO3 coating after corrosion were characterized by XRD and SEM, respectively. The reaction between the two powders of SrZrO3 and CMAS did not occur at 1150 oC, whereas occurred at 1250 oC for 1 h, which resulted in the formation of corrosion products of ZrSiO4, CaZrO3, SrAl2O4 and t-ZrO2, and then a new phase of m-ZrO2 did additionally appear for 4 h corrosion. The corrosion product of t-ZrO2 was formed on the SrZrO3 coating surface after CMAS attack, and the phase transition from t-ZrO2 to m-ZrO2 occurred as the corrosion time increased, the formation of the corrosion products could suppress the further corrosion of the SrZrO3 coating by CMAS.

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    Influence of Heat Treatment on Microstructure of Composite Coatings of FeAl-Cr3C2
    Yao CHEN,Honghua ZHANG,Ganlan YANG,Junhuai XIANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 58-62.   DOI: 10.11902/1005.4537.2016.193
    Abstract   HTML   PDF (924KB)

    Composite coatings of Fe40Al-50%Cr3C2 with the thickness of 30 μm were prepared by high velocity oxygen-fuel (HVOF) technology on 304 steel. The change of its microstructure by heat treatment at different temperatures was studied by means of XRD and SEM/EDS. The surface of the coating is very rough and the element distribution is inhomogeneous before the heat treatment. The composition of the coating is mainly composed of Fe, Al, intermetallics plus a little oxide of Fe and Al. A large amount of particles of Fe with big size are present in the outer layer, while a few particles of Al are present in the inner layer. The homogeneity of the coating has great change after vacuum annealing, though some holes still exist in the coating. With the increase of the annealing temperature from 700 ℃ to 900 ℃, the pure Fe and Al particles of big size disappear gradually due to their full diffusion and thereby formation of more intermetallics.

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    Corrosion and Conductivity Behavior of TiN Coating on 304 Stainless Steel Bipolar Plates
    Jie SHEN,Wei LIU,Tiegang WANG,Taijun PAN
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 63-68.   DOI: 10.11902/1005.4537.2016.149
    Abstract   HTML   PDF (746KB)

    TiN coating was prepared on the surface of 304 stainless steel by plasma spraying technology. The microstructure and phase composition of the coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion performance of the 304 stainless steel without and with TiN coating was assessed by the potentiodynamic polarization and electrochemical impedance in the simulated proton exchange membrane fuel cell solutions containing 0.3 mol/L H2SO4 plus 2 mg/L HF. Moreover, electrical conductivity of them was also compared. The results indicated that TiN coating significantly increased the free corrosion potential of the steel and induced a decrease of the corresponding corrosion current density by one order of magnitude, which is attributed to the presence of the continuous and compact coating of about 20 μm in thickness. During the whole period of 360 h immersion, the open circuit potential of the coating was obviously higher than that of the bare substrate, suggesting the excellent stability of coating. The impedance of the coating decreased slightly with immersion time but still remained in high level, suggesting that the TiN coating could provide the effective protection for the substrate. The interface contact resistance of the TiN coating was about 50 mΩcm-2 by an applied load of 138 Ncm-2, obviously smaller than that of the bare 304 stainless steel, exhibiting better conductivity.

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    Cyclic and Static Oxidation Behavior of Fe-Cu-Ni-Al Alloy at 900 ℃
    Bin XIAO,Junhuai XIANG,Honghua ZHANG
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 69-73.   DOI: 10.11902/1005.4537.2016.194
    Abstract   HTML   PDF (731KB)

    The static and cyclic oxidation behavior of Fe-65Cu-15Ni-5Al and Fe-45Cu-15Ni-5Al alloyshas been investigated in air at 900 ℃ respectively. In the case of static oxidation, the oxidation rate of Fe-65Cu-15Ni-5Al is much lower than that of Fe-45Cu-15Ni-5Al. The oxidation kinetics of Fe-65Cu-15Ni-5Al obeys parabolic law during the first oxidation stage, followed by a linear law, while that of Fe-45Cu-15Ni-5Al obeys parabolic law in the whole oxidation period. However, In the case of cyclic oxidation, Fe-65Cu-15Ni-5Al shows a much faster oxidation rate than Fe-45Cu-15Ni-5Al. For the above two cases, the formed scales are both composed of an outermost thick CuO layer, a middle layer is mainly composed of mixture of oxides of Fe, Ni and Al, together with their compounds. Internal oxidation only occurs for the Fe-65Cu-15Ni-5Al alloy statically oxidized. While in other cases, discontinuous inner layer of Al2O3 is present, which is connected with the internal oxidation region of Al. In the case of cyclic oxidation, the scale of inner Al2O3 layer of Cu-rich Fe-65Cu-15Ni-5Al alloy has undergone rupture easily due to the presence of high stress, resulting in high corrosion rate. On the contrary, in the case of static oxidation at 900 ℃ the critical Al content needed to form a protective outer Al2O3 layer in the α phase has been reached, which can fairly well explain its better oxidation resistant than Fe-45Cu-15Ni-5Al.

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    Rapid Identification of Liquid Accelerant in Fire Scene Environment
    Dongbai XIE,Guo SHAN
    Journal of Chinese Society for Corrosion and protection. 2017, 37 (1): 74-80.   DOI: 10.11902/1005.4537.2016.154
    Abstract   HTML   PDF (1233KB)

    Oxidation tests of Cu and Q235 steel were conducted in air alone and a combustion atmosphere of kerosene-air mixture at 600, 700 and 800 ℃ respectively, the later aims to simulate the fire scene environment with the presence of fuel accelerant. Cracking and spallation of the formed oxide scales were observed by using optical microscopy. The results revealed that the existence of kerosene accelerated the oxidation of Cu and Q235, and changed the surface morphologies of the oxide scales. With the increasing temperature and time, serious spallation of the oxide scales was observed. Especially, due to the spallation of the oxide scale formed on Cu, the mass loss of Cu did occurr. Based on the features of the oxide scales formed on Cu and Q235, it is expected to offer complementary insight on determining the fire characteristics, such as exposure temperature, time period and whether liquid accelerant is involved.

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