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    Original Article
    Inhibition Performance of a New 3,5-dibromosalicylaldehyde-2-thenoyl Hydrazine Schiff Base for Carbon Steel in Oilfield Water and Relevant Molecular Dynamics Simulation
    LIU Jie, LIU Zheng, LIU Jin, XIE Siwei
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 101-111.  DOI: 10.11902/1005.4537.2013.069
    Abstract   HTML   PDF (5764KB) ( 1123 )
    A new 3,5-dibromosalicylaldehyde-2-thenoyl hydrazine Schiff base compounds (L2) was synthesized. Its inhibition performance and adsorption behavior for carbon steel in a simulated oilfield water were investigated by electrochemical methods, scanning electron microscopy and molecular dynamics simulation respectively. The results indicated that L2 exhibits excellent corrosion inhibition performance for carbon steel in the simulated oilfield water, and also that in simulated oilfield waters with various pH values at different temperatures. The molecular dynamics simulation results proved that L2 molecules may parallel be adsorbed on the steel surface firmly via several reactive sites and packed together to form a dense monolayer to prevent the metal surface from water and corrosive medium in the liquid. In addition, L2 molecule monolayer can suppress the inwards migration of corrosive species. That is why L2 exhibits excellent corrosion inhibition performance.
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    Effect of SRB on Corrosion Behavior of X70 Steel in a Simulated Soil Solution
    LIU Tong, ZHANG Yanfei, CHEN Xu, WANG Dan, CHEN Yu, WANG Guangfu
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 112-118.  DOI: 10.11902/1005.4537.2013.220
    Abstract   HTML   PDF (3513KB) ( 453 )
    The corrosion behavior of X70 steel was studied in a simulated soil solution with and without sulfate-reducing bacteria (SRB) by means of weight-loss measurement, SEM-EDS analysis and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion rate increased with time in the solution without SRB, while the corrosion product film was loose and non-protective. In the solution with SRB, however, a compact and homogeneous biofilm formed on the steel surface, which could suppress the mass transfer so that to mitigate the steel corrosion, whilst the corrosion product film became loose and apt to spall because of the increasing amount of absorbed substance and sulfide in the corrosion product with time, in consequence the corrosion of the steel substrate was further promoted. The stability of the inner portion of the corrosion product film was related to the distribution of deposits on the steel in the solution without SRB. The porous extracellular polymeric substances (EPS) formed on the steel in the solution with SRB played a role in barrier action to the mass transfer during the activated process.
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    Oxidation Behavior of Ferritic-martensitic Steel P92 Exposed to Supercritical Water at 600 ℃/25 MPa
    XU Hong, YUAN Jun, ZHU Zhongliang, ZHANG Qian, ZHANG Naiqiang
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 119-124.  DOI: 10.11902/1005.4537.2013.085
    Abstract   HTML   PDF (2656KB) ( 811 )
    The oxidation behavior of ferritic-martensitic P92 steel was studied in supercritical waters containing different dissolved oxygen of 0, 100 and 300 μg/L at 600 ℃ under 25 MPa. The results show that a typical double-layered oxide scale is formed on all the samples, which consists an outer layer Fe-rich magnetite and an inner layer Cr-rich Fe-Cr spinel. Cracks on the surface of oxide scales are found at the initial oxidation stage, which is different from the experimental phenomenon in supercritical water at 550 ℃. A distinct gap between inner oxide layer and substrate alloy is observed in some regions of the sample which is exposed to the supercritical water containing 300 μg/L dissolved oxygen. The mechanism concerning the influence of dissolved oxygen on oxidation behavior and the gap formation is further discussed.
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    Effect of Pentaerythritol Glycoside on Performance of Passive Film Formed on Steel Rebar in Saturated Ca(OH)2 Solution Containing 3.5%NaCl
    ZHOU Xin, CHEN Ren, YANG Huaiyu, WANG Fuhui
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 125-130.  DOI: 10.11902/1005.4537.2013.102
    Abstract   HTML   PDF (4309KB) ( 845 )
    The effect of PG (pentaerythritol glycoside) on the performance of the passive film on steel rebar in Ca(OH)2 saturated solution containing 3.5%NaCl, which was designed to simulate solutions in concrete pores, was investigated by mean of polarization curve measurement, Mott-Schottky analysis technique and surface analysis. The results showed that the PG could enhance the stability of the adsorption film formed on the metal surface. The curves of Csc-2 vs E of the steel rebar electrodes follow a linear Mott-Schottky (M-S) relationship with a positive slope in the range of potential from -0.5 to -0.1 V (vs SCE) in the M-S measurements, suggesting the passive film formed on the steel rebar surface was n-type semi-conductor. Moreover, with increasing concentration of inhibitor, the carrier density in passive film decreases, indicating that the passive film formed on steel rebar surface in the presence of PG was more compact and stable rather than that in the absence of inhibitor, and the corrosion resistance of passive film is gradually enhanced.
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    Effect of Aging Temperature on Microstructure and Corrosion Behavior of 15-5PH Precipitation Hardened Stainless Steel
    HUA Xiaozhen, HUANG Jinhua, NIE Lun, ZHOU Xianliang, PENG Xinyuan
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 131-137.  DOI: 10.11902/1005.4537.2013.080
    Abstract   HTML   PDF (8388KB) ( 401 )
    The effect of aging treatment temperature on the evolution of the microstructure and corrosion resistance of 15-5PH stainless steel was studied by means of XRD, SEM and TEM as well as immersion test and measurements of polarization curve and electrochemical impedance spectroscopy. The results show that the martensitic structure of the steel is gradually decomposed to be finer with the increase of aging temperature, while NbC particles precipitate in between martensitic laths. Spherical particles of Cu-rich phase is separated out at aging temperature 550 ℃. Austenite was observed at 580 ℃ implying the reverse conversion from martensite to austenite occurs due to over ageing. With the increase of aging temperature, the Cu-rich phase change into coherent from incoherent, which gathered to growth as short rod at 620 ℃; the corrosion weight loss rates increase; the corrosion potential decrease; Ac impedance values reduced and therefore the corrosion resistance of the steel degraded.
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    Analysis of Electrochemical Noise by Hilbert-Huang Transform and Its Application
    SHI Wei, DONG Zehua, GUO Xingpeng
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 138-146.  DOI: 10.11902/1005.4537.2013.099
    Abstract   HTML   PDF (3495KB) ( 925 )
    Time-frequency transition plays a key role in the pattern identification of electrochemical noise (EN) signal. In this paper, we studied the EN of carbon steel in simulated concrete pore solution by Hilbert-Huang transform (HHT), and found that, in comparison with discrete wavelet transform (DWT), HHT exhibited much higher resolution and stability at time-frequency domain for the identification of EN transients. Moreover, HHT can improve the resolving accuracy of metastable pit signals coupled in EN. According to the EN characteristics of carbon steel at different corrosion status, such as passive, metastable, and stably growing pits, we proposed a pitting factor (PF) as an index for identification and quantification of localized corrosion type based on HHT algorithm, aiming at the diagnosis of corrosion type and severity of industrial installation by online EN monitoring instrument.
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    Evaluation of Soil Corrosivity for Ground Grid of Substations in an Area by Factor Analysis
    ZHU Zhiping, WANG Leijing, PEI Feng, YIN Zhaohui, WU Fayuan, TIAN Xu
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 147-152.  DOI: 10.11902/1005.4537.2013.074
    Abstract   HTML   PDF (691KB) ( 517 )
    Soils in a depth corresponding to half length of the buried grouding grids are sampled from sites of 123 substations of a 110 kV transmission network in an area. Their physical and chemical properties (11 indexes) are measured, which then are analyzed and processed by using the method of factor analysis. The results show that soil corrosivity for substation ground grid in this area is mainly influenced by calcium and magnesium ions, pH value, chloride ion and water content. A comprehensive evaluation is made based on these five key corrosive factors. It follows that the soil corrosivity for substation ground grids in this area may be divided into four levels as: exceptionally strong (11 substations), strong (86 substations), relatively strong (14 substations) and middle (12 substations). Meanwhile, the corrosivity of all the soil samples are evaluated according to German Beckman standard method. The results of the two methods are in accord with each other, which indicates that factor analysis can be applied to evaluate the soil corrosivity for substation ground grid with a good reliablility.
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    Polarization Performance of Two Aluminium AlloySacrificial Anodes
    LIANG Hu, DU Min, ZHANG Youhui
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 153-159.  DOI: 10.11902/1005.4537.2013.091
    Abstract   HTML   PDF (1499KB) ( 828 )
    The polarization performance of two kinds of Al-Zn-In-Mg-Ti sacrificial anodes at different potential was studied by open circuit potential, constant current test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the anodes were difficult to dissolve because of an oxide scale could form at open circuit potential. After an impressed current was applied to the anodes, the electric double layer capacitance gradually increased, the polarization resistance was gradually reduced, the oxide film gradually ruptured. With the increasing of polarization potential, the anode current increased rapidly, while the polarization resistance decreased and finally became stable. The anode with smaller polarization resistance exhibited a good electrochemical performance, which was consistent with the 4 d evaluation results by an accelerated test.
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    Electrochemical Noise Analysis of Local Pitting Corrosion Behavior of Pure Aluminum
    LIU Shiqiang, WANG Lida, ZONG Qiufeng, ZHANG Cheng, LIU Guichang
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 160-164.  DOI: 10.11902/1005.4537.2013.056
    Abstract   HTML   PDF (1313KB) ( 608 )
    The local pitting corrosion behavior of the pure aluminum in 3.5%NaCl solution was characterized by electrochemical noise analysis technique. The corrosion processes for aluminum were studied in detail by analyzing time-domain and frequency-domain characteristics of electrochemical noise together with morphology features. The results show that the time-domain spectroscopy of the electrochemical noise can be used to predict the occurrence of local corrosion and qualitatively distinguish the type of corrosion. It was found that the current standard deviation σI, noise resistance Rn and current white noise levels W can reflect the corrosion intensity. When the corrosion occurs, σI and W tend to increase, but Rn tends to decrease.
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    Corrosion Behavior of N6 and Monel400 Nickel Alloy in Deep Sea Environment of South China Sea
    SUN Feilong, LU Lin, LI Xiaogang, XIAO Kui, WU Junsheng, WANG Song
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 165-170.  DOI: 10.11902/1005.4537.2013.104
    Abstract   HTML   PDF (5009KB) ( 1033 )
    The corrosion behavior of N6 nickel and Monel400 nickel alloy in 800 and 1200 m deep sea environment of South China Sea was studied by field test. The morphology and composition of corrosion product were examined by means of SEM, EDS and XRD techniques. The results indicated that the resistance to localized corrosion of Monel400 nickel alloy was better than that of N6 nickel. The green corrosion product of N6 nickel was composed of NiCl26H2O with a small amount of CaCO3 and MgCO3, under which severe tunnel corrosion occurred, while localized corrosion induced perforation even took place on N6 nickel samples. However, shallow and large size corrosion pits formed on Monel400 nickel alloy, which were covered by green corrosion product consisted of (CuNi)2Cl(OH)3. Comparing with the data of literatures, the maximum pit depth of N6 and Monel400 nickel alloy decreased as the depth of test side increased.
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    Corrosion Resistance of Zr-1Nb-xGe Alloys in Superheated Steam at 400 ℃
    ZHANG Jinlong, TU Liming, XIE Xingfei, YAO Meiyi, ZHOU Bangxin
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 171-177.  DOI: 10.11902/1005.4537.2013.084
    Abstract   HTML   PDF (2620KB) ( 664 )
    The corrosion resistance of Zr-1Nb-xGe(x=0, 0.05, 0.1, 0.2, mass fraction, %) alloys was investigated in superheated steam at 400 ℃, 10.3 MPa by autoclave tests. The microstructures of the alloys and oxide scales on the corroded specimens were observed by SEM and TEM. The results show that the corrosion resistance of the Zr-1Nb alloy in superheated steam at 400 ℃, 10.3 MPa may be enhanced by Ge addition. The alloy with 0.05% Ge shows the best corrosion resistance. In Zr-1Nb-xGe alloys, there are four types of second phase particles (SPPs), including β-Nb, Zr(Nb,Fe,Cr)2, Zr(Nb,Fe,Cr,Ge)2 and coarse Zr3Ge SPPs, and the maximum solid solubility of Ge in the α-Zr matrix of Zr-1Nb alloy is 0.05%~0.1%. It is noted that the Ge solid soluted in the α-Zr matrix can effectively slow down the microstructural evolution of oxide scale, thereby enhancing the corrosion resistance of the alloy. When the Ge content exceeds its solid solubility, Ge was precipitated as Zr(Nb,Fe,Cr,Ge)2 and Zr3Ge SPPs. The coarse Zr3Ge SPPs will decrease the corrosion resistance of the alloys.
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    Corrosion Behavior of Equal-channel-angular-pressedZn-22Al Alloys in NaCl Aqueous Solution
    ZENG Xuduo, YANG Lijing, ZHANG Yangming, SONG Zhenlun
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 178-184.  DOI: 10.11902/1005.4537.2013.096
    Abstract   HTML   PDF (8632KB) ( 272 )
    The influence of equal-channel-angular-press (ECAP) process on the corrosion behavior of Zn-22Al alloy in 3.5% (mass fraction) NaCl solution has been studied by means of immersion test and electrochemical measurement. The results showed that the microstructure of the alloy was refined by ECAP process with much uniform grain size distribution rather than that of the as-cast one. Al-rich phase of the ECAP alloy was preferentially corroded in the corrosion process, leading to the isolation and then falling off from the alloy of the Zn-rich phase surrounded by Al-rich phase, therewith the corrosion rate was enhanced. This phenomenon might be ascribed to the increase of grain boundaries, stress and defects of the alloy induced by ECAP process. In general, with the increasing pass of ECAP, the weight loss of the alloy in immersion test increased, while the corrosion current density increased and the corrosion potential decreased, therewith the corrosion resistance was degraded with the increasing ECAP pass for the alloy.
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    Effect of Nd Addition on Corrosion Resistance of AM60 Magnesium Alloy
    ZHOU Jing, FENG Zhiyong, ZHANG Jinling, WANG Shebin
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 185-191.  DOI: 10.11902/1005.4537.2013.095
    Abstract   HTML   PDF (3781KB) ( 399 )
    The corrosion behavior of AM60 alloy with different Nd content (0%~1.2%, mass fraction) in 3.5%NaCl solution was studied by means of immersion test and potention dynamic polarization measurement, as well as scanning electronic microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). The results show that the addition of rare earth Nd in AM60 alloy can refine grains and strengthen grain and phase boundaries of the alloy. The addition of rare earth Nd may play rolls in shifting positively the corrosion potential of the alloy, decreasing the contact area between the activated Mg and H+, and slowing down the effect of Mg17Al12 on the corrosion of α phase in the alloy. Therefore, the corrosion resistance of AM60 alloy is enhanced by the addition of Nb effectively.
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    Effect of Zn Addition on Behavior of Deposited Co in Oxide Scales of Alloys in PWR Primary Water
    DUAN Zhengang, ZHANG Lefu, JIANG Suqing, SHI Xiuqiang, XU Xuelian
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 192-194.  DOI: 10.11902/1005.4537.2013.090
    Abstract   HTML   PDF (2752KB) ( 596 )
    In order to simulate the deposition of Co oxide on the surface of PWR structural materials during service, oxide scales doped with Co on stainless steels 316 and 304, and alloy 690 were prepared by soacking them in a high temperature solution containing Co ions. Then the effect of Zn addition on the behavior of the deposited Co in oxide scales was studied in a simulated PWR primary water with Zn addition at 315 ℃. The results show that the presence of Co changes the morphology of oxide scales, while in the simulated PWR water the added Zn may displace the deposited Co in the oxide scales.
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    Performance of FeCl3 Etching Solution Renewed by Ion-exchange Membrane Electrolysis
    BAO Jiqing, SHEN Xiaofang, XU Jie, YU Tian
    Journal of Chinese Society for Corrosion and protection, 2014, 34 (2): 195-198.  DOI: 10.11902/1005.4537.2013.100
    Abstract   HTML   PDF (638KB) ( 514 )
    In order to recycle the etching solution, the waste FeCl3 etching solution of a plant was renewed by a process of ion-exchange membrane electrolysis. Then the performance of the renewed etching solution was evaluated in terms of the effect of etching time, temperature, concentration of the etching solution and the free acid content in the etching solution on the redox potential and the etching rate for etching solutions such as new etching solution, the online etching solution and renewed etching solution. The results showed that the renewed etching solution met the demands of the etching process. An optimal etching efficiency may be reached when the etchant contains 90% of the renewed etching solution and free acid concentration higher than 0.3 mol/L at etching temperatures within a range 50~60 ℃.
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