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Oxidation Kinetics of 9Ni Steel Billet at High Temperature
Using a combined thermal analysis and mass spectrometer system, The thermal and kinetic behaviors of oxidation of 9Ni steel slab at 900℃ ~ 1250℃ were investigated by field emission scanning electron microscopy (FE-SEM), field emission electron probe microscopy (FE-EPMA), X-ray diffraction (XRD) and. . .
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Current Issue More>>
      15 February 2023, Volume 43 Issue 1 Previous Issue   
    Research Progress on Protection and Self-healing Performance of Layered Double Hydroxides Coatings on Mg-alloy
    ZHAO Yanliang, ZHAO Jingmao
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 1-5.   DOI: 10.11902/1005.4537.2022.030
    Abstract   HTML   PDF (543KB)

    Layered double hydroxides (LDHs) coatings have great application prospects in the field of metallic corrosion and protection due to their physical barrier function to corrosive ions and ion exchange characteristics. This article reviews the recent research and development of corrosion inhibitor of intercalated LDH, which is used to protect Mg-alloy against corrosion. It also discusses the preparation and evaluation approach for self-healing performance of novel LDH coatings. Finally, the future research direction is prospected in terms of the shortcomings related to the current research.

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    Research Progress on Corrosion of Metal Interconnector for Solid Oxide Fuel Cells
    WANG Bihui, XIAO Bo, PAN Peiyuan, LIU Ju, ZHANG Naiqiang
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 6-12.   DOI: 10.11902/1005.4537.2022.049
    Abstract   HTML   PDF (1831KB)

    Ferritic stainless steels are used in solid oxide fuel cell (SOFC) as interconnect materials, which present low cost and good workability, and high electroconductivity. However, the harsh environment limits their use in SOFC stack. This paper introduces the current research status of corrosion of metallic interconnectors, summarizing researches on the influence of the air, fuel, dual atmosphere, alloying elements, and internal contact environment. The corrosion mechanism of interconnect material and the shortcomings of the research on the corrosion behavior of interconnectors, as well as the direction of future development were systematically described.

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    Research Progress on Corrosion Behavior of Metallic Materials in Acetic Acid Environment
    LIU Mingming, YANG Xiaobing, CHEN Xiaoqi, WANG Zhengbin, ZHENG Yugui, HE Chunlin
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 13-21.   DOI: 10.11902/1005.4537.2022.186
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    Acetic acid is an important raw material and plays an important role in the modern chemical industry. However, acetic acid is highly corrosive, which can easily cause corrosion of metallic components, threatening the service safety of equipment. In order to better understanding and preventing the corrosion induced by acetic acid, this paper summarizes the mechanisms, influencing factors (temperature, acetic acid concentration and impurities) and protection measures for corrosion of metals in acetic acid, on the basis of practical corrosion failure cases. It is expected to provide some guidance for selecting proper materials and taking effective measures to protect components serving in acetic acid environments from corrosion.

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    Research Progress on Monitoring Techniques for Corrosion Under Insulating Layer
    WANG Weijie, HAN Jicheng, MAO Yang, GUAN Zichao, DI Zhigang, MIAO Lei, MA Shengjun
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 22-28.   DOI: 10.11902/1005.4537.2022.039
    Abstract   HTML   PDF (932KB)

    This paper reviews the research status of several technologies such as electrochemical noise, capacitive imaging, radio frequency identification, infrared thermography, distributed fiber optics, microwave, etc. in the application of monitoring and detection of corrosion under insulating layer (CUI). According to the history of the concerned CUI risks, the adopted CUI monitoring and detection technologies can be classified as three kinds, which are related to premise-, middle- and late-stages of the CUS risks to be examined respectively. It is discussed that the monitoring and detection technology for premise-stage is used to speculate the tendency of CUI, the monitoring and detection technology for later-stage can only detect the irreversible damage of metal loss to a certain extent. At the present, CUI monitoring and detection technology still has the problem in the inadequate data interpretation, while the accuracy and precision of the technology itself need to further be improved. This paper looks forward also to the future research direction in this field.

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    Current Situation and Prospect of On-line Monitoring Technology for Atmospheric Corrosion Testing of Metallic Materials
    ZHOU Mengxin, WU Jun, FAN Zhibin, ZHOU Xuejie, CHEN Hao
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 38-46.   DOI: 10.11902/1005.4537.2022.027
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    The on-line monitoring technology for atmospheric corrosion testing of metallic materials and coatings is reviewed. The relevant principle and research status of many on-line monitoring methods, such as resistance probe method, galvanic corrosion cell, electrochemical impedance spectroscopy, electrochemical noise method, surface ultrasonic technology, quartz crystal microbalance technology and radio frequency identification technology are introduced. Meanwhile, the electrochemical method, non-electrochemical method and the combination of different methods are described. Finally, the existed problems to be solved, which related with the current online monitoring of atmospheric corrosion, are summarized, and the future research directions of online monitoring technology of atmospheric corrosion are also prospected in terms of the so called "Internet plus" intelligent anticorrosion rout and the development of corrosion big data.

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    Localized Corrosion of 5083 Al-alloy in Simulated Marine Splash Zone
    MAO Yingchang, ZHU Yu, SUN Shengkai, QIN Zhenbo, XIA Da-Hai, HU Wenbin
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 47-54.   DOI: 10.11902/1005.4537.2022.162
    Abstract   HTML   PDF (8785KB)

    Besides seawater and marine atmosphere, the service environment of marine equipment such as ships and amphibious aircraft also involves wave splashing. In this work, a corrosion platform in simulated splash zone is constructed, which consists of a simulated splash device and an electrochemical sensor. The localized corrosion of 5083 Al-alloy in simulated splash zone is investigated by using open circuit potential (OCP) measurement, electrochemical impedance spectroscope (EIS) combined with morphology analyses. Experimental results indicate that, compared with the corrosion in the full immersion zone, the alloy suffer severe pitting corrosion, intergranular corrosion and exfoliation corrosion, with a corrosion depth about 40~80 μm. The shape of the pits in the splash zone is closely related to the water flow direction. Under the joint action of the shear force of water flow and corrosion, lamellar exfoliation occurs at the bottom edge of the pit, resulting in a slow change in the depth of the pit with terraced inner walls. The high oxygen content and high seawater splash rate are the main cause of the high localized corrosion susceptibility in the splash zone. There are only scattered small pits of about 5 μm in depth, in the full immersion zone, and most of them originate from inclusions, whilst the inclusion serves as the cathode phase and the surrounding aluminum alloy matrix behaves as anode and is dissolved. EIS fitting results by using the Measurement Model show that the polarization resistance of the 5083 Al-alloy in the splash zone is 20%-50% of that in the full immersion zone, while the effective capacitance is about twice as large as that of the full immersion zone, indicating that the corrosion rate of the splash zone is higher than that of the full immersion zone. A larger effective capacitance in the splash zone corresponds to a coarser surface on which the corrosion products are accumulated.

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    Oxidation Behavior of a Single Crystal Ni-based Superalloy N5 and Its Nanocrystalline Coating at 900 ℃ in O2 and O2+20%H2O Environment
    YANG Yifan, SUN Wenyao, CHEN Minghui, WANG Jinlong, WANG Fuhui
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 55-61.   DOI: 10.11902/1005.4537.2022.040
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    The nanocrystalline coatings of superalloy N5 were deposited on the surface of nickel-based single-crystal superalloy N5 by magnetron sputtering. The oxidation behavior of the single-crystal alloy and its nanocrystalline coating in environments of O2 and O2+20%H2O at 900 ℃ was investigated, respectively. The results show that the water vapor accelerates the oxidation rate of the bare alloy and the coating, while promotes very specially the spallation, and affects the composition and structure of the oxide scales formed on the bare alloy. Correspondingly, the formed oxide scales composed of an outer layer NiO, a middle layer NiAl2O4 and an inner layer Al2O3 for the bare alloy being oxidized in environments of O2 and O2+H2O respectively, meanwhile, the oxidation rate is higher, and the spallation of outer oxide scale dose emerge for the oxidation in O2+H2O environment. The nanocrystalline coating significantly can enhance the high temperature oxidation resistance of the coated alloy. After oxidation in O2, Al2O3 is formed on the surface of the coating, while in O2+H2O environment, the formed oxide scale is NiAl2O4. Meanwhile, no cracks and spalling were found on the surface of oxide scale, which played a good protective role.

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    Preparation and Corrosion Resistance of Ternary Layered Compound Cr2AlC Coating on 304 Stainless Steel for Bipolar Plates of PEMFC
    LIU Yun, REN Yanjie, CHEN Jian, ZHOU Libo, QIU Wei, HUANG Weiying, NIU Yan
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 62-68.   DOI: 10.11902/1005.4537.2022.008
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    In this paper, Cr2AlC phase coatings were deposited on 304 stainless steel bipolar plates by DC magnetron sputtering. The morphology and microstructure of the coating were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and its corrosion behavior in 0.01 mol/L H2SO4 solution was investigated by electrochemical methods. The results showed that the as-deposited Cr2AlC coating was compact and uniform, mainly composed of Cr2AlC phase. The corrosion current density of the coating was 2.43×10-7 A·cm-2, which was lower than that of 304 stainless steel by two orders of magnitude. After potentiostatic polarization at 600 and -240 mVSCE, the corresponding current densities were 2.44×10-8 and 2.3×10-7 A·cm-2, respectively. In addition, the impedance modulus of Cr2AlC coating in 0.01 mol/L H2SO4 solution was higher than 105 Ω·cm2, indicating that the coating could provide excellent protection for 304 stainless steel bipolar plate of PEMFC.

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    Friction-corrosion Performance of Steels and Their Welding Zone for Composite Plate of 317L Stainless Steel/FH40 Low-temperature Marine Steel in Simulated Sea Waters at Different Temperatures
    SUN Shibin, ZHAO Ziming, GAO Zhenpeng, GONG Xuhui, WANG Dongsheng, QIANG Qiang, CHANG Xueting
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 69-76.   DOI: 10.11902/1005.4537.2022.013
    Abstract   HTML   PDF (11417KB)

    The performance of friction and corrosion of FH40 steel, 317L stainless steel and their welding zone of the explosive formed composite plate of FH40 steel/317L stainless steel was studied via UMT-2 multifunctional friction-wear tester with a grinding ball of alumina (Al2O3) in simulated environments of sea water and sea ice, respectively at different temperatures. Their microstructure and wear morphology were characterized by metallographic microscope, white light interferometer and scanning electron microscope. The results showed that with the decrease of temperature, from 20 ℃ to -20 ℃, the friction coefficient and wear loss of FH40 steel and the welding zone increase significantly, while 317L stainless steel changed only little. It should be emphasized on that the wear and corrosion loss of 317L stainless steel is much lower than that of FH40 steel and the welding zone in sea water, which confirmed the feasibility of 317L stainless steel as the shell material for icebreaker. In addition, the corrosion resistance of the steels was also assessed by means of measurements of electrochemical impedance and polarization curves in order to determine the effect of low temperature environment on the corrosion resistance of composite steel plate. The results showed that the corrosion rate of the welding zone was lower than FH40 steel both at room temperature and low temperature.

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    Synergistic Inhibition Effect of Cuscuta Chinensis Lam Extract and Potassium Iodide on Cold Rolled Steel in Hydrochloric Acid
    WU Hao, DENG Shuduan, LI Xianghong
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 77-86.   DOI: 10.11902/1005.4537.2022.037
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    Cuscuta chinensis Lam extract (CCLE) was obtained from the dodder, which is a kind of parasitic plant, by circulation reflux method. The synergistic inhibition effect of CCLE and KI on cold rolled steel in 1.0 mol/L HCl solution was studied by mass loss method, potentiodynamic polarization curve measurement and electrochemical impedance spectroscope, as well as electron microscope (SEM) and atomic force microscope (AFM). The results showed that CCLE acts as an efficient inhibitor for cold rolled steel in HCl solution, and the maximum inhibition efficiency is 84.0%. The inhibition can be further increased to 90.8% for the combination of CCLE with KI. All the synergism parameters are higher than unity for the design of various compound concentrations and test temperatures. The adsorption of CCLE and CCLE/KI obey Langmuir isotherm. When CCLE is incorporated with KI, both of the adsorption equilibrium constant (K) and the absolute value of standard adsorption free energy (ΔG0) becomes larger. CCLE and CCLE/KI can be arranged as mixed-type inhibitors, and the inhibition coefficient is strengthened after combination. There exists a single capacitive loop in the Nyqusit diagram. The charge transfer resistance turns to be much higher for the combination of CCLE with KI. SEM and AFM observation result also proves that the combination of CCLE and KI presents a significantly synergistic inhibition effect on the surface of cold rolled steel in HCl solution.

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    Corrosion Behavior of 300M Ultra High Strength Steel in Simulated Marine Environment
    LI Han, LIU Yuanhai, ZHAO Lianhong, CUI Zhongyu
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 87-94.   DOI: 10.11902/1005.4537.2022.035
    Abstract   HTML   PDF (14467KB)

    The corrosion performance of the 300M steel was assessed via artificial seawater immersion testing and neutral salt spray testing, aiming to simulate the operation environments, by means of electrochemical methods (i.e. OCP, EIS, PDP) and modern instruments (i.e. SEM+EDS, XRD, CLSM etc.). The results show that 300M ultra high strength steel is sensitive to the change of pH for artificial seawater. With the decrease of pH, the cathodic curve changes from oxygen reduction to hydrogen evolution process control, and the open circuit potential (OCP) moves positively, the charge transfer resistance decreases, and the corrosion current density increases. The fitting results of polarization curve and Nyquist diagram indicate that the decrease of pH leads to the acceleration of corrosion. The corrosion rate calculated by mass loss method shows that the corrosion in salt spray testing is more serious than that in artificial seawater immersion testing. However, in the above two cases the steel all presents characteristics of uniform corrosion. This was further proved by observation results of surface morphology and cross-sectional morphology of the tested steel. The corrosion products thickened with local spallation as the progress of corrosion process. The corrosion products was composed of α-FeOOH, γ-FeOOH, α-Fe2O3 and Fe3O4, the more the α-FeOOH. The difference in corrosion behavior of the 300M steel by immersion testing and salt spray testing is determined by the corrosion electrochemical reaction process and the deposition process of corrosion products. During the salt spray testing, the steel surface covered by thin electrolyte film with adequate oxygen supply, which promotes the deposition of corrosion products, thus promoting the adsorption of Cl-, and ultimately accelerating the corrosion.

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    Corrosion Behavior of Weld Joint of 690 MPa Weathering Bridge Steel in Simulated Industrial Atmosphere
    CHENG Peng, LIU Jing, MU Wenguang, HUANG Feng, HUANG Xianqiu, PANG Tao
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 95-103.   DOI: 10.11902/1005.4537.2022.104
    Abstract   HTML   PDF (14150KB)

    The corrosion behavior of weld joint of 690 MPa weathering bridge steel in simulated industrial atmosphere was investigated by periodic accelerated corrosion test, coupled with electrochemical test, scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and other surface characterization techniques. The results show that in the early stage of corrosion, due to the difference of microstructure, the corrosion resistance of the weld zone composed mainly of ferrite is better than that of the base material composed mainly of bainite, the heat affected zone with bainite microstructure has the worst corrosion resistance due to the coarsened and non-uniformly distributed grains, however the potential difference between different areas of the welded joint does not cause galvanic corrosion. In the later stage of corrosion, Cu and Cr are obviously enriched in the rust layer in different areas of the welded joint, while Ni content in the rust layer at the weld zone is much higher than that at the base metal zone and the heat affected zone. Due to the large alloying element content in the weld zone, where the rust layer is more smooth and compact and has higher polarization resistance and impedance value,which may result in better corrosion resistance of the whole welded joint rather than the base metal.

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    Preparation and Corrosion Resistance of Zn-Al Coating on Sintered NdFeB Permanent Magnet
    JIANG Jie, JIANG Jianjun, YANG Lijing, LEI Bufang, ZHAO Yu, LIN Jianqiang, SONG Zhenlun
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 104-110.   DOI: 10.11902/1005.4537.2022.003
    Abstract   HTML   PDF (7196KB)

    A Cr-free Zn-Al coating was prepared via a two-step process, namely spraying Zn-Al paste and subsequently baking, on the surface of sintered Nd-Fe-B permanent magnet, and which was further examined by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, and differential thermal comprehensive thermal analyzer (TG-DTA) in terms of its morphology, composition, and formation mechanism of the coating. The corrosion behavior of the coated Nd-Fe-B magnet was studied via immersion testing in 3.5%NaCl solution, and neutral salt spray testing. The results show that Zn-Al coating is uniformly coated on the surface of the NdFeB magnet, the coating thickness is about 27 µm, while, its corrosion resistance to neutral salt spray testing is higher than 1000 h; In other word, the Cr-free Zn-Al coating can provide excellent cathodic protection and physical barrier for NdFeB permanent magnet.

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    Effect of Temperature on Stress Corrosion Behavior of Ti-alloy Ti80 in Sea Water
    LI Wenju, ZHANG Huixia, ZHANG Hongquan, HAO Fuyao, TONG Hongtao
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 111-118.   DOI: 10.11902/1005.4537.2022.028
    Abstract   HTML   PDF (8445KB)

    In order to promote the application of Ti80 alloy for marine engineering, the influence of temperature variation on the stress corrosion behavior of the Ti-alloy was studied via constant displacement stress corrosion test and slow strain rate tensile test (SSRT), as well as electrochemical impedance spectroscopy, Mott-Schottky curve measurement, three-dimensional video microscopy and scanning electron microscopy (SEM). The results show that in atmospheric pressure and temperature range of 5-35 ℃, with the decrease of temperature, the stress corrosion cracking sensitivity index of Ti80 alloy gradually increases, the value of critical strength factor K1SCC gradually decreases, and the stress corrosion tendency increases. In low-temperature seawater, the fractured surface of Ti80 alloy even presents characteristics of locally river-like and tearing ridge-like quasi-cleavage. This may be ascribed to that on the local area around the crack tip, the formed passivation film possesses small resistance, while there exists more defects, and easy stacking of dislocations, thus resulted in local stress concentration in the passivation film, further due to the synergy of the existed film stress and the applied stress, the crack nucleation and expansion may speed up, therewith damages on the passivation film may be hard repaired, and thus the stress corrosion rate may spontaneously be accelerated.

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    Corrosion Behavior of B10 Cu-Ni Alloy Pipe in Static and Dynamic Seawater
    WANG Xiao, LIU Feng, LI Yan, ZHANG Wei, LI Xiangbo
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 119-126.   DOI: 10.11902/1005.4537.2022.024
    Abstract   HTML   PDF (9281KB)

    The corrosion behavior of B10 Cu-Ni alloy in static and dynamic seawater was studied by using a loop test device with in-situ measurement accessory. The corrosion rate, electrochemical characteristics, corrosion morphology and corrosion products of B10 alloy were characterized by means of mass loss method, electrochemical impedance spectroscope (EIS), scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). The results show that the corrosion rate of the alloy in static and dynamic seawater gradually decreased with time, while the formed corrosion product film was compact. The products generated on the B10 alloy in static seawater composed mainly of Cu2O, but NiO, Cu2O and FeOOH for that in flowing seawater. It is noted that the presence of NiO and FeOOH may be beneficial to the reduction of corrosion reaction rate and the enhancement of corrosion resistance of B10 alloy. In other word, the seawater erosion may facilitate the formation of the compact corrosion product film to protect the substrate. The study can provide an experimental basis for the evaluation of the quality corrosion product film on B10 alloy and the service performance of B10 alloy served as pipeline in dynamic seawaters.

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    Galvanic Corrosion Behavior of 20# Steel/Tin Bronze Couple in Flowing Seawater
    LIU Jinzeng, XING Shaohua, QIAN Yao, ZHANG Dalei, MA Li
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 127-134.   DOI: 10.11902/1005.4537.2022.001
    Abstract   HTML   PDF (9719KB)

    The galvanic corrosion of the couples of 20# steel penetrating cabin parts and tin bronze valve is the severely corroded parts in the sea water pipeline system of ships. In order to control the galvanic corrosion of the couple 20# steel/tin bronze to extend the life of the seawater pipeline system, the galvanic potential and galvanic current of the couple 20# steel pipe/tin bronze pipe in static and flowing sea water of 1, 3, and 5 m/s were assessed in-situ, respectively. Whilst, the variations of galvanic corrosion rate with time and flow rate were acquired; At the same time, scanning electron microscope (SEM) and laser Raman spectrometer were used to analyze the corrosion morphology and the composition of corrosion products. The results show that there is an obvious galvanic corrosion tendency between 20# steel and ZCuSn5Pb5Zn5 in seawater of different flow rates, namely 20# steel acts as the anode, and presents intensified corrosion tendency, while ZCuSn5Pb5Zn5 acts as the cathode. The anodic polarization current density of 20# steel and the cathodic polarization current density of ZCuSn5Pb5Zn5 increase significantly in flowing seawater rather than in static seawater, therewith the galvanic corrosion is significantly intensified. The galvanic couple in flowing seawater of 1 m/s presents a corrosion rate 17.5 times higher than that in static seawater. When the seawater flow rate reaches 5 m/s, a corrosion product scale with higher compactness and low activity is formed on the surface of 20# steel, and the galvanic corrosion rate decreases.

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    Effect of SiCp Size on Microstructure and Corrosion Properties of Cast AZ91 Mg-alloys
    LV Xin, DENG Kunkun, WANG Cuiju, NIE Kaibo, SHI Quanxin, LIANG Wei
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 135-142.   DOI: 10.11902/1005.4537.2022.006
    Abstract   HTML   PDF (17910KB)

    The sub-micron SiCp, micron SiCp and dual-scale SiCp reinforced AZ91 Mg-alloy based composites, namely composites (S1), (M10), and (S1+M9) respectively, were prepared by semi-solid stirring casting method. They were then characterized by means of optical microscope, scanning electron microscope, X-ray diffraction, immersion method, and electrochemical test, etc in terms of the effect of the particle size of SiCp on the microstructure and corrosion properties of the as-cast AZ91 Mg-alloys. The results show that the addition of SiCp can refine significantly the semi-continuous network-like Mg17Al12 phase in the AZ91 Mg-alloy, which is attributed to the heterogeneous nucleation effect of SiCp on the Mg17Al12 phase. The Mg17Al12 phase can be precipitated as Mg17Al12 particles with core of sub-micron SiCp, and/or directly on the surface of micron SiCp. By comparing the two composites reinforced with the same volume fraction of SiCp, it can be found that the corrosion resistance of S1+M9 is significantly lower than that of M10, indicating that when the content of SiCp is constant, changing the size of SiCp from micron to sub-micron will reduce the corrosion resistance of the composites.

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    Effect of Heat Treatment Process on Corrosion Resistance of Ti6321 Alloy
    ZHANG Jiahuan, CUI Zhongyu, FAN Lin, SUN Mingxian
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 152-158.   DOI: 10.11902/1005.4537.2022.023
    Abstract   HTML   PDF (8271KB)

    The effect of heat treatments on the microstructure and corrosion behavior of Ti6321 Ti-alloy in artificial seawater and 5 mol/L hydrochloric acid solution was investigated by means of XRD, electrochemical tests, SEM and confocal laser scanning microscope. Results show that the three groups of Ti6321 Ti-alloy, which has been subjected to three different heat treatments, exhibit excellent passivation ability in artificial seawater with more or less the same level of corrosion resistance. In 5 mol/L HCl solution, the corrosion resistance of the Ti6321 Ti-alloy with widmanstatten structure is the worst, followed by equiaxed ones, while the alloy with double structure presents the best corrosion resistance.

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    Molecular Simulation on Oxidation Mechanism of FeCr Alloy in High Temperature Steam Environment
    SHENG Ganwen, QI Jing, LU Ping, XU Hong, HONG Miaomin
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 159-165.   DOI: 10.11902/1005.4537.2022.074
    Abstract   HTML   PDF (4629KB)

    The reaction of FeCr alloy, as tube material of the ultra (super) critical unit, with high-temperature steam may result in the formation a protective oxide scale. However, the spallation of the oxide scale can easily lead to tube burst failure and seriously endanger the safe operation of the unit. Based on the molecular dynamics of the ReaxFF reaction, this paper reveals the mechanism related with the high-temperature steam oxidation of FeCr alloy on atomic scale. The results showed that at the initial oxidation stage, the Cr atoms on the surface of the alloy could induce the steam decomposition, and the inwardly diffused O atoms oxidized the alloy to form an inner FeCr oxide. Subsequently, under the inner oxide growth stress, the metal atoms migrated outward layer by layer. Due to the difference in the diffusion rate of Fe atoms and Cr atoms in the oxide scale, a double-layered oxide scale was formed, which was consistent with the experimental observations. The steam temperature has an important influence on the steam oxidation characteristics of FeCr alloys. With the increasing steam temperature, the protective effect of the formed oxide scale on the alloy gradually decreased.

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    Effect of Sand Grain Size on Cavitation Erosion of Concrete Induced by High Velocity Sand Carrying Water Flow
    DONG Zhiyong, XU Xuyi, LI Yuhang
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 166-172.   DOI: 10.11902/1005.4537.2022.083
    Abstract   HTML   PDF (8247KB)

    Effect of the variation of sand grain size on cavitation erosion of concrete in sand-bearing water flow was experimentally investigated via a small looped water tunnel. Sand grains with five typical median particle sizes (0.08, 0.25, 1, 2 and 3 mm) were obtained by sieving method. For each grain size, the sand-bearing water samples with the same sand content S=12 kg/m3 for each given sand grain size were prepared respectively. The sand content of high-speed sand carrying water flow was real-timely measured by an infrared suspended solid analyzer. The pressure at the working section of the water tunnel for each sand-carrying flow with a given grain size was acquired by pressure data acquisition system in real-time, then of which a comparison was made with the case of clear water. Concrete specimens with water-cement ratio W/C=0.4, cement-sand ratio C/S=1.5,7 d aging strength fcu,k=17.8 MPa were poured. Afterwards, the specimen was placed into a specimen box fixed in the working section of water tunnel to undergo cavitation erosion test for 4 h by different flow speeds for one sand carrying water with a given sand grain size. The results showed that for the case with send content of S=12 kg/m3 and flow speed V=38.2 m/s, the flow pressure at cavitation zone decreased with the increase in sand grain size, which resulted in decrease in the incipient cavitation number and promoted the formation of cavitation; the sand carrying flow pressure at cavitation-erosion zone increased with the increase in sand grain size, which could promote the cavitation erosion. The cavitation erosion level of the concrete specimen was aggravated with the increase in sand grain size, and the cavitation erosion range was further spread with the increasing flow velocity.

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    Corrosion Inhibition of Vetiver Extract on Steel in Hydrochloric Acid Environment
    DENG Zhihua, LEI Ran, ZHANG Zhiyong, YANG Weiyu, LI Xianghong
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 173-178.   DOI: 10.11902/1005.4537.2022.065
    Abstract   HTML   PDF (1854KB)

    Vetiveria zizanioides was extracted by reflux extraction method to obtain vetiver extract (VZE). The corrosion inhibition of a cold rolled carbon steel by VZE in 1.0 mol/L hydrochloric acid solution was investigated by means of mass loss measurement and electrochemical methods. The results showed that the best corrosion inhibition was achieved by a dose of 0.20 g/L VZE at 30 ℃, with a corrosion inhibition rate of 91.9%. The adsorption of VZE on the steel surface conforms to the Langmuir adsorption isotherm, and the adsorption type is a mixed adsorption type of combined physical and chemical adsorption. The dynamic potential polarization curve shows that VZE can inhibit both the cathodic and anodic reactions, and is a mixed inhibition type corrosion inhibitor. With the increase of VZE concentration, the electrochemical impedance spectrum capacitive arc increases significantly, the charge transfer resistance of steel increases, and the corrosion reaction rate decreases. In other word, the VZE can provide good corrosion inhibition for the cold rolled carbon steel in 1.0 mol/L hydrochloric acid solution.

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    Corrosion Behavior of X65 Steel by AC Interference and Cathodic Protection
    LI Changchun, HE Renbi, CHEN Yilong, HE Renyang, WANG Zhengxiao
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 179-185.   DOI: 10.11902/1005.4537.2022.016
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    The corrosion behavior of pipeline steel under the combined action of the applied alternating stray current and cathodic protection was assessed via a home-made stray current corrosion testing device, mass loss measurement and electrochemical methods. The results show that with the increase of AC current density, the corrosion potential of pipeline steel is negatively shifted and the metal corrosion tendency is enhanced. AC interference promotes the anodic oxidation reaction in the positive half cycle of AC and then increases the corrosion rate of pipeline steel. With the increase of AC frequency, the corrosion process of the pipeline steel is shortened for each cycle of AC, the Faraday current, as promoter for metal oxidation reaction is suppressed, therewith the corrosion rate of pipeline steel is reduced. The corrosion rate of pipeline steel increases in strong acid or alkali environment.

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    Corrosion Resistance of Q690 High Strength Steel in Simulated Corrosive Environment of Ocean Splash Zone
    WEI Huanhuan, ZHENG Dongdong, CHEN Chen, ZHANG Dawei, WANG Kaili
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 186-190.   DOI: 10.11902/1005.4537.2022.042
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    The surface of steel structural components exposed to extremely harsh environments is prone to rust, as a result, their normal service life is reduced, whilst the durability problem is increasingly prominent. Thus, the corrosion behavior and characteristics of surface morphology of Q690 high strength steel was assessed via alternative cyclic tests: immersion in artificial sea water, drying by indoor ventilation air and drying in atmosphere of 95% (±3%) relative humidity at 35 ℃, aiming to simulate the corrosive environment of ocean splash zone. Then, the variation of surface morphology with the progress of corrosion process and the corresponding surface coordinate parameters were collected by laser confocal microscope (LSCM). The results show that in the initial stage of corrosion, a small number of needle-like pits occurred on the surface, and the metallic luster was gradually lost. With the progress of corrosion process, the initial needle-like pits gradually developed toward large pits. At the later stage of corrosion, there exist a large number of lamellar corrosion products, and on which, exfoliations in some local areas could be observed. In addition, according to the microscopic scanning analysis, it could be seen that the cumulated corrosion products exhibited a good protective effect on the steel substrate, the corrosion process rapidly extended to the periphery and finally corrosion products completely covered the whole surface of steel specimen. When the corrosion period was 100 d, the volume loss rate and surface corrosion height were 1.38% and 840 μm, respectively.

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    Corrosion Behavior of Typical Grounding Materials in Artificial Alkaline Soil Solution
    GAO Zhiyue, JIANG Bo, FAN Zhibin, WANG Xiaoming, LI Xingeng, ZHANG Zhenyue
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 191-196.   DOI: 10.11902/1005.4537.2022.061
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    The corrosion behavior of three metal materials (Q235 steel, galvanized steel and pure copper) in an artificial solution, aiming to simulate the typical alkaline soil solution of Shandong province, was studied by means of electrochemical testing technique, optical metallographic microscope and laser confocal microscope (CLSM). The results show that the corrosion degree of the three metal materials is varied in the simulated alkaline soil solution. The anodic processes of them are all metal dissolution, while the cathodic processes are all oxygen absorption reaction. The corrosion resistance of Q235 steel is the worst. Q235 steel and galvanized steel show the characteristics of uniform corrosion. Pitting occurs on the surface of pure copper. Generally, the corrosion resistance of the three metals may be ranked as follows: pure copper>galvanized steel>Q235 steel.

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    Laboratory Simulation of Crud Deposition on Zr-alloy Fuel Cladding in Simulated Pressurized Water Reactor Primary Coolant
    LIAO Jiapeng, MAO Yulong, JIN Desheng, LI Jinggang
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 197-201.   DOI: 10.11902/1005.4537.2022.022
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    For pressurized water reactor (PWR) nuclear power plant, crud on fuel cladding is derived from primary corrosion products, which deposit on the surface of fuel assembly. Crud deposition is affected by the coupling effects between the primary coolant environment and the thermal-hydraulic condition. The crud on cladding surface can affect the operation safety and economic benefits of the reactor. In this paper, the main factors affecting the crud deposition behavior on the surface of fuel cladding were described. The crud deposition process on the domestic Zr-alloy cladding was assessed via a home-made experimental set. As a result, the porous and chimney-like crud was successfully reproduced, while which composed mainly of NiFe2O4, Fe2O3 and NiO, besides the precipitation of LiBO2 was detected. The experiment results indicated that the crud deposition on PWR fuel cladding could be reliably reproduced through laboratory simulation.

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    AC Corrosion Behavior of Several Metallic Materials as Candidate for Boiler Electrode
    ZHENG Zhong, ZHOU Yuanxiang, LI Yongyin
    Journal of Chinese Society for Corrosion and protection. 2023, 43 (1): 202-208.   DOI: 10.11902/1005.4537.2021.357
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    Corrosion resistance of electrode materials is an important factor affecting energy consumption and service life of electrode boiler. In this paper, the corrosion resistance of titanium, 304 stainless steel and 20# steel as candidate electrode materials was assessed by controlling the applied current density to simulate the working condition of electrode boiler. The corrosion rate, polarization potential and conductivity of the three electrode materials were measured before and after corrosion in different concentrations of trisodium phosphate solution by different applied voltages. The results show that the corrosion current density of 20# steel is about 4 and 20 times higher than that of 304 stainless steel and titanium respectively. Loose corrosion products are generated on the surface of 20# steel electrode, and thus its corrosion resistance is the worst. Results of comparative tests show that titanium electrode has the best corrosion resistance, but its price is high; 304 stainless steel cannot completely be passivated by 500 A/m2 AC interference, thereby pitting corrosion occurs on its surface. By taking comprehensively the corrosion resistance, conductivity and economy into consideration, stainless steel may be the suitable candidate as electrode material in the case of long boiler life expectancy.

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