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目录 contents

    摘要

    采用SEM、EDS、电化学测试等方法研究了热浸镀用Zn-5Al-xMn(x=0,0.1,0.2,0.3)合金的铸态组织与耐蚀性能。结果表明:在Zn-5Al合金中加入少量的Mn显著抑制了粗大初生β-Zn相的生成,当Mn含量为0.2%时,初生β-Zn相最少,共晶组织占比最高。试验合金的自腐蚀电位随着Mn含量的提高而增大,自腐蚀电流密度先减小后增大。Zn-5Al-0.2Mn合金自腐蚀电流最小为1.403 μA/cm2,其高频阻抗和低频扩散阻抗均最大。Zn-5Al合金中初生β-Zn相优先腐蚀,Zn-5Al-0.2Mn合金因初生β-Zn相较少,发生均匀性腐蚀,其腐蚀产物在Zn-5Al-xMn合金中最致密。

    Abstract

    The microstructure and corrosion behavior of the as-cast hot-dip Zn-5Al-xMn (x=0,0.1,0.2,0.3) alloys have been investigated by SEM, EDS, electrochemical test techniques, etc. The results indicate that a small addition of Mn in as-cast Zn-5Al alloy can greatly inhibit the formation of primary β-Zn phase. When the Mn addition is 0.2% (in mass), the amount of β-Zn phase is the least and the percentage of eutectic composition reaches the maximum. The corrosion potential of the tested alloy moves positive direction, while the corrosion current density decreases first and then increases as increasing of Mn addition. The corrosion current density of the Zn-5Al-0.2Mn alloy has the minimum value of 1.403 μA/cm2, with which the impedance spectra at both high and low frequencies reach the maximum. The primary β-Zn phase is corroded preferentially in Zn-5Al alloy, but uniform corrosion happens in Zn-5Al-0.2Mn alloy for little amount of β-Zn phase. The corrosion products of Zn-5Al-0.2Mn is the most compact in the Zn-5Al-xMn alloys.

    Galfan(Zn-5Al-0.1RE)合金是20世纪70年代国际铅锌组织(ILZRO)研制开发的具有共晶显微结构特征的热浸镀层合金,共晶Zn-Al合金(共晶成分为质量分数为5.02% Al,共晶温度382 ℃)比纯锌熔点低37.5 ℃,热浸镀工艺温度比Galvalume合金镀层(640 ℃)低200 ℃。在热浸镀生产的快速凝固条件下易造成镀层共晶合金组织中出现初生β-Zn相,因原电池反应优先发生腐蚀而降低了合金的耐蚀性能。加入少量稀土元素尽管有细化晶粒、净化锌液的作用,但难以抑制β-Zn相析[1,2]。Zn-Al合金中添加适量的Mn,与Zn和Al形成A15(MnZn),Al9(MnZn)2等高熔点富锰三元相在基体内或沿晶界呈不连续分布,从而抑制合金中初生β-Zn生长并增加共晶组织含量,提高了合金的耐腐蚀性[3,4,5]。Zhang[6]对纯锌中加入0.4%Mn后的腐蚀试验研究表明,Zn5(CO3)2(OH)6)易沉积于腐蚀膜孔隙中而提高其致密性,从而显著降低了腐蚀反应速率。然而,目前未见关于Mn对共晶Zn-5Al合金耐蚀性能的影响报道,本文研究了微量Mn对Zn-5Al合金铸态组织及耐蚀性能的影响。

  • 1 实验方法

    1

    试验材料为纯锌、纯铝及Al-10Mn中间合金。试验合金按表1所述的配比将纯锌、纯铝和Al-10Mn合金放入坩埚电阻炉中,炉料全部熔化后升温至550 ℃进行搅拌,静置15~20 min后降温至420 ℃时浇注到125 mm×150 mm×25 mm的铜铸模中。试验合金铸态组织和表面腐蚀形貌采用XJP-300型光学显微镜和JSM-6360LV扫描电镜观察。

    表1 Zn-Al合金的名义成分(质量分数)(%)

    Tab.1 Nominal composition of Zn-Al alloy (in mass)(%)

    AlloyAlMnZn
    15Bal.
    250.1Bal.
    350.2Bal.
    450.3Bal.

    腐蚀速率试样尺寸为10 mm×10 mm×10 mm的试样。将表面打磨并抛光的试样用无水酒精擦洗并烘干,然后将试样放入3.5%NaC1(质量分数,下同)溶液中室温浸泡480 h。浸泡前的试样称重并记为m1,按照GB/T 16545—2015去除浸泡试样表面腐蚀产物后的质量为m2,按式(1)计算腐蚀试样失重率V

    V=m1-m2At × 100%
    (1)

    式中:V为试样腐蚀速率,g/(m2·d);m1为试样浸泡前的质量,g;m2为试样经浸泡并去除腐蚀产物后的质量,g;A为试样表面积,cm2t为试样浸泡时间,d。

    试验合金的电化学性能采用CHI660A型电化学工作站测试,采用铂电极为辅助电极、饱和甘汞电极为参比电极、待测热浸镀用锌铝合金为工作电极的三电极体系。试样用环氧树脂胶封装,工作表面面积为1 cm2,腐蚀介质为3.5% NaCl溶液,待极化电位稳定后测试。极化曲线测量的极化电位范围为−1 800~−500 mV,动电位扫描速率为1 mV/s。电化学交流阻抗谱测量在开路电位下进行,工作电极和铂电极的间距保持约50 mm,激励信号幅值为10.0 mV的正弦波,扫描频率范围为10−2~105 Hz,结果采用ZSimpWin软件拟合分析。

  • 2 实验结果及分析

    2
  • 2.1 Zn-5Al-xMn合金的显微组织

    2.1

    1 所示为铸态Zn-5Al-xMn合金的显微组织。由图1可知,Zn-5Al合金的铸态组织由粗大的初生树枝晶β-Zn相和层片状锌铝共晶组织组成,Zn-5Al-0.1Mn的合金中初生β-Zn相数量减少且晶粒明显细化,Zn-5Al-0.2Mn合金中初生β-Zn相最少,Zn-5Al-0.3Mn合金中出现了条块状的新相。从Zn-5Al-0.3Mn合金铸态组织中条块状相方框区的Al、Mn和Zn的原子比EDS分析结果可知,条块状Al-Mn-Zn新相为Al8(Mn, Zn)5(图2[3,4,5]。从β-Zn相组织形态上看,随着含Mn量的增加,β-Zn相由粗大树枝晶转变为近等轴的颗粒,外形逐渐圆化。综上所述,添加Mn显著抑制了铸态Zn-5Al合金中初生β-Zn相的生成,增加了层状Zn-Al共晶组织占比,当合金中Mn含量为0.2%时,Zn-5Al合金中共晶组织所占比例最大。

    图1
                            铸态Zn-5Al-xMn的显微组织

    图1 铸态Zn-5Al-xMn的显微组织

    Fig.1 Metallographic structure of cast Zn-5Al-xMn alloys

    图2
                            铸态Zn-5Al-0.3Mn合金的SEM像和EDS谱

    图2 铸态Zn-5Al-0.3Mn合金的SEM像和EDS谱

    Fig.2 SEM image and EDS patterns of cast Zn-5Al-0.3Mn alloy

  • 2.2 Zn-5Al-xMn合金的耐腐蚀性能

    2.2
  • 2.2.1 腐蚀失重

    2.2.1

    3为Zn-5Al-xMn合金在3.5% NaCl溶液中浸泡480 h后的腐蚀速率。Zn-5Al合金的腐蚀速率最大(3.88 μg·cm−2·d−1),加入Mn降低了合金的腐蚀速率,其中Zn-5Al-0.2 Mn合金的腐蚀速率最小(1.17 μg·cm−2·d−1),表明添加适量Mn提高了Zn-5Al合金的耐腐蚀性能。

    图3
                            Zn-5Al-xMn合金的腐蚀速率

    图3 Zn-5Al-xMn合金的腐蚀速率

    Fig.3 Corrosion rate of Zn-5Al-xMn alloys

  • 2.2.2 电极电位

    2.2.2

    自腐蚀电位是表征金属材料发生腐蚀反应难易程度的一个重要参数,Zn-5Al-xMn合金在3.5% NaCl中性水溶液中自腐蚀电位与浸泡时间的关系曲线如图4所示。由图可知,Zn-5Al-xMn合金的自腐蚀电位随浸泡时间的增加而升高,其原因在于在3.5% NaCl中性水溶液中合金电极表面腐蚀产物使合金自腐蚀电位升高。Zn-5Al合金的自腐蚀电位随着Mn含量的提高而增大,但Mn含量超过0.2%后,Mn对Zn-5Al合金自腐蚀电位的影响减弱。

    图4
                            Zn-5Al-xMn合金在3.5%NaCl中性水溶液中自腐蚀电位与浸泡时间的关系曲线

    图4 Zn-5Al-xMn合金在3.5%NaCl中性水溶液中自腐蚀电位与浸泡时间的关系曲线

    Fig.4 Relationship between the corrosion potential Ecorr and the exposure time in 3.5% NaCl solution

  • 2.2.3 极化曲线

    2.2.3

    5为Zn-5Al-xMn合金在3.5% NaCl溶液中的极化曲线。Mn含量的变化并未改变Zn-5Al合金极化曲线形状,表明其具有相同的电极反应过程。根据法拉第定律,合金的腐蚀速率v与其腐蚀电流密度Icorr成正[4]

    图5
                            Zn-5Al-xMn合金在3.5%NaCl溶液中的极化曲线

    图5 Zn-5Al-xMn合金在3.5%NaCl溶液中的极化曲线

    Fig.5 Polarization curves of Zn-5Al-xMn alloys in 3.5% NaCl solution

    v=MnFIcorr=3.73×10-4×Icorr×M/n
    (2)

    式中:v为合金的腐蚀速率,g·m−2·h−1M为金属的原子质量,g·mol−1n为反应中转移电子的物质摩尔量,mol;F为法拉第常数,其值为26.8 A·h;Icorr为腐蚀电流密度,μA·cm−2

    2为采用Tafel曲线拟合获得的Zn-5Al-xMn合金的阳极塔菲尔斜率ba、阴极塔菲尔斜率bc和腐蚀电流密度Icorr[7,8]。与Zn-5Al合金相比,加入Mn降低了合金的阴、阳极塔菲尔斜率,表明Mn抑制了Zn-5Al合金的阴、阳极反应速率。Zn-5Al合金的自腐蚀电流密度Icorr随着Mn含量的升高先减小后增大,Zn-5Al-0.2 Mn合金的自腐蚀电流密度Icorr最小(1.4 μA·cm−2),结合式(2)分析同样表明,Mn含量为0.2%时的合金耐腐蚀性能最好。

    表2 极化曲线拟合所得的ba, bcIcorr

    Tab.2 Values of Icorr, ba and bc, deduced from polariza-tion measurements

    Alloy

    bc/(mV·

    decade-1)

    ba/(mV·

    decade-1)

    Icorr/(μA·cm-2)
    Zn-5Al56346.4
    Zn-5Al-0.1Mn43274.2
    Zn-5Al-0.2Mn27181.4
    Zn-5Al-0.3Mn32233.2
  • 2.2.4 电化学交流阻抗图谱

    2.2.4

    交流阻抗图谱是用于研究金属腐蚀机理的有效手段,在3.5% NaCl溶液中浸泡不同时间的Zn-5Al-xMn合金Nyquist图如图6所示。Zn-5Al-xMn合金的Nyquist图由高频段容抗弧和低频段斜线组成。高频容抗弧的半径越大,腐蚀反应进行得越缓慢,对应合金的耐蚀性能越[9]。随着浸泡时间的越长,Zn-5Al-xMn合金高频容抗弧半径增大,其原因在于合金表面的腐蚀产物随着腐蚀的进行而越积越厚,导致参与电化学反应的有效活性表面积减小,同时致密的腐蚀产物阻碍了Zn2+,Cl-等离子的扩散,从而保护了合金基体。低频段呈现出Warburg(沃伯格)阻抗特征,因Warburg阻抗出现前有高频容抗弧,其相位角偏离45°[10],表明合金的腐蚀过程由电化学反应控制转变为扩散过程控制,这主要是因为氧的去极化阴极反应(0.5O2+H2O+2e → 2OH)导致溶液中氧含量随着腐蚀的进行而降低,同时合金电极表面生成的较为致密的腐蚀产物Zn(OH)2和ZnAl2O3显著降低了氧(其体积较大且呈中性)的扩散能力,导致腐蚀过程受到抑[2]

    图6
                            在3.5%NaCl溶液中浸泡不同时间的Zn-5Al-xMn合金Nyquist图

    图6 在3.5%NaCl溶液中浸泡不同时间的Zn-5Al-xMn合金Nyquist图

    Fig.6 Nyquist diagrams of Zn-5Al-xMn under different exposure times in 3.5% NaCl solution

    注:根据Zn-5Al-xMn合金腐蚀过程特点,对其电化学阻抗谱数据进行拟合,建立了等效电路模型RsQRtZWRl))(图7)。常相位角元件Q=[Y·(n]-1,其中Y为表征Q的导纳,Ω-1·cm-2·s-nj=(-1)1/2ω是角频率;n是与电极表面粗糙度相关的量纲一指数,n值在实验中范围为0.7~0.8[11]Rs为饱和甘汞电极参比电极的鲁金毛细管口到工作电极间的溶液电阻,R1为发生阴极去极化反应时的电荷转移电阻,Rt为发生阳极溶解反应Zn+2OH- → Zn(OH)2+2e-时的电荷转移电阻,ZW为Warburg阻[12]

    根据拟合电路图7,高频容抗弧半径RH=RlRt/( Rl+Rt)值的计算结果如图8[2]。在相同的浸泡时间条件下,加入Mn增大了合金的高频容抗弧半径,但当Mn含量超过0.2%时,合金高频容抗弧半径有所减小;同时,Zn-5Al-xMn合金的高频容抗弧半径随着浸泡时间的延长而增大,其原因在于电极表面的腐蚀产物随着腐蚀的进行而逐渐增多、增厚,造成活性面积减小和离子穿越腐蚀产物膜的阻力增大,从而使R1Rt值增大。

    图7
                            Zn-5Al-xMn合金电化学阻抗谱数据拟合建立的等效电路

    图7 Zn-5Al-xMn合金电化学阻抗谱数据拟合建立的等效电路

    Fig.7 Equivalent circuit for fitting the EIS data of Zn-5Al-xMn alloys

    图8
                            Zn-5Al-xMn合金在3.5%NaCl溶液中RH随浸泡时间的变化

    图8 Zn-5Al-xMn合金在3.5%NaCl溶液中RH随浸泡时间的变化

    Fig.8 Variation of the resistance RH as a function of immersing time for Zn-5Al-xMn alloys in 3.5% NaCl solution

    腐蚀产物膜中的离子扩散主要通过膜中微观通道,腐蚀产物膜的孔隙度与扩散系数D成反比。与扩散过程相关的Warburg阻抗ZW可用式(3)表[13]

    ZW=1Y0jω
    (3)

    式中:Y0是表征ZW的导纳,与扩散系数D1/2成反比。腐蚀产物膜的孔隙度越大,D值因离子越容易穿过腐蚀产物膜而增大,因而表征ZW的导纳Y0越大。从Y0值的拟合结果图可以看出(图9),在相同浸泡时间下,加入Mn降低了合金的导纳值Y0,但当Mn含量超过0.2%时,合金导纳值Y0有所增大,表明Mn含量为0.2%的合金在腐蚀过程中对氧扩散抑制作用最强;此外,合金的导纳Y0值随着浸泡时间的增大而减小,进一步说明腐蚀初期由电化学反应控制,合金表面锌铝腐蚀产物膜随着腐蚀进行而变厚,从而使Y0值变小,腐蚀过程逐渐转变为扩散过程控制。

    图9
                            Zn-5Al-xMn合金在3.5%NaCl溶液中Y0随浸泡时间的变化

    图9 Zn-5Al-xMn合金在3.5%NaCl溶液中Y0随浸泡时间的变化

    Fig.9 Variation of Y0 as a function of immersing time for Zn-5Al-xMn in 3.5% NaCl solution

  • 2.3 Zn-5Al-xMn合金的腐蚀形貌

    2.3

    Zn-5Al合金组织若全部为层状共晶组织体时,在腐蚀过程中其整体均匀的组织能够避免合金组织中初生相和共晶体因电极电位不同而优先发生选择性腐蚀。图10为Zn-5Al-xMn合金在3.5%NaC1溶液中静置不同时间后的腐蚀显微组织图。Zn-5Al合金优先在初生β-Zn相处腐蚀,初生β-Zn相表面随着静置时间的延长逐渐被呈团絮状腐蚀产物覆盖;添加0.3%Mn的合金中初生β-Zn的数量大大减小(图1),并且形成的Al-Mn-Zn三元相因其耐腐蚀性较高而难以发生优先腐蚀。

    Zn-5Al-xMn合金在中性3.5% NaCl溶液中浸泡480 h后SEM腐蚀形貌如图11所示。Zn-5Al合金表面形成疏松的块状腐蚀产物,Zn-5Al-0.1Mn合金在块状腐蚀产物下的腐蚀产物变得细小致密,Zn-5Al-0.2Mn合金表面上的腐蚀产物最为细小、均匀致密,而对Zn-5Al-0.3Mn合金表面的腐蚀产物再次变大,同时出现的孔洞又为离子向合金内部扩散提供了通道而有利于进行腐蚀反应。因此,Zn-5Al-0.2Mn合金表现出最好的耐蚀性。

    图10
                            实验合金在3.5%NaCl溶液中静置不同时间后的腐蚀显微组织

    图10 实验合金在3.5%NaCl溶液中静置不同时间后的腐蚀显微组织

    Fig.10 Corrosion morphology of experimental alloys etching in 3.5% NaCl solution

    图11
                            Zn-5Al-xMn合金在中性3.5%NaCl溶液中浸泡480 h后SEM腐蚀形貌

    图11 Zn-5Al-xMn合金在中性3.5%NaCl溶液中浸泡480 h后SEM腐蚀形貌

    Fig.11 SEM morphology of Zn-5Al-xMn alloys after 480 h exposure in 3.5% NaCl solution

  • 3 结 论

    3

    (1) Zn-5Al合金铸态组织由粗大的初生树枝晶β-Zn相和层片状锌铝共晶组织组成,加入少量的Mn显著抑制了粗大初生β-Zn相的生成,当Mn含量为0.2%时,初生β-Zn相最少,共晶组织占比最高;Zn-5Al-0.3Mn合金中出现了条块状的Al8(Mn, Zn)5新相。

    (2) 加入少量Mn显著降低了Zn-5Al合金的腐蚀速率,Zn-5Al-0.2Mn合金腐蚀速率和自腐蚀电流密度最小,分别为1.17 mg·cm-2·d-1和1.403 μA/cm2;Zn-5Al-xMn合金的高频阻抗和低频扩散阻抗均随浸泡时间的延长而增大,Zn-5Al-0.2Mn合金的高频及低频阻抗均最大。

    (3) Zn-5Al-xMn合金优先从初生β-Zn相处发生选择性腐蚀, Zn-5Al-0.2Mn合金表面产生的腐蚀产物最致密。

  • 参考文献

    • 1

      刘子利, 刘希琴, 王怀涛, 等.Ti 对Zn-5Al 合金组织及耐腐蚀性能的影响[J].中国腐蚀与防护学报,2014,34(6):515-522.

      LIU Zili, LIU Xiqin, WANG Huaitao, et al. Effect of Ti addition on microstructure and corrosion property of Zn-5Al alloy[J]. Journal of Chinese Society Corro-sion Protection, 2014,34(6):515-522.

    • 2

      ROSALBINO F, ANGELINI E, MACCIO D, et al. Application of EIS to assess the effect of rare earths small addition on the corrosion behaviour of Zn-5%Al (Galfan) alloy in neutral aerated sodium chloride solution[J]. Electrochimica Acta, 2009, 54(4):1204-1209.

    • 3

      王先德, 王建华, 苏旭平, 等. 锰对ZZnAl4Y锌合金显微组织和力学性能的影响[J]. 铸造, 2010, 59 (3):312-314.

      WANG Xiande, WANG Jianhua, SU Xuping, et al. Effect of manganese on microstructure and mechanical properties of ZZnAl4Y zinc alloy[J].Foundry,2010,59(3):312-314.

    • 4

      LI Y Y, LUO J M, LUO Z Q, et al. The microstructure and wear mechanism of a novel high-strength, wear-resistant zinc alloy (ZMJ)[J]. J Mater Process Tech, 1995, 55(3/4):154-161.

    • 5

      MUNZ R, WOLF G K, GUZMAN L, et al. Zinc/manganese multilayer coatings for corrosion protection[J]. Thin Solid Films, 2004, 459(1/2):297-302.

    • 6

      ZHANG B, ZHOU H B, HAN E H, et al. Effects of a small addition of Mn on the corrosion behaviour of Zn in a mixed solution[J]. Electrochimica Acta, 2009, 54(26):6598-6608.

    • 7

      SHI Z, LIU M, ATRENS A. Measurement of the corrosion rate of magnesium alloys using Tafel extrapolation[J]. Corrosion Science, 2010, 52(2): 579-588.

    • 8

      曹楚南. 腐蚀电化学原理[M]. 北京: 化学工业出版社, 2004.

      CAO Chunan. Corrosion theory[M]. Beijing: Chemical Industry Press, 2004.

    • 9

      SOUTO R M, FERNANDEZ M L, GONZALEZ S, et al. Comparative EIS study of different Zn-based intermediate metallic layers in coil-coated steels[J]. Corrosion Science, 2006, 48(5): 1182-1192.

    • 10

      孙敏, 肖葵, 董超芳, 等. 带腐蚀产物超强度钢的电化学行为[J]. 金属学报, 2011, 47(4):442-448.

      SUN Min, XIAO Kui, DONG Chaofang, et al. Elec-trochemical behaviors of ultra high strength steels with corrosion products[J]. Acta Metallurgica Sinica, 2011, 47(4):442-448.

    • 11

      HAMLAOUI Y, PEDRAZA F, TIFOUTI L. Corrosion monitoring of galvanized coatings through electrochemical impedance spectroscopy[J]. Corrosion Science, 2008, 50(6):1558-1566.

    • 12

      李党国, 冯耀荣, 白真权, 等. 温度对N80碳钢CO2腐蚀产物膜性能的影响[J]. 中国腐蚀与防护学报, 2008, 28(6):369-373.

      LI Dangguo, FENG Yaorong, BAI Zhenquan, et al. Effect of temperature on properties of CO2 corrosion scale of N80 carbon steel[J]. Journal of Chinese Society Corrosion Protection, 2008, 28(6):369-373.

    • 13

      陈长风, 路民旭, 赵国仙, 等. 腐蚀产物膜覆盖条件下油套管钢CO2腐蚀电化学特征[J]. 中国腐蚀与防护学报, 2003, 23(3):139-143.

      CHEN Changfeng, LU Minxu, ZHAO Guoxian, et al. Electrochemical characteristics of CO2 corrosion of well tube steels with corrosion scales[J]. Journal of Chinese Society Corrosion Protection, 2003,23(3):139-143.

崔军

机 构:常熟开关制造有限公司, 常熟,215500

Affiliation:Changshu Switch Manufacturing Co Ltd, Changshu, 215500, China

角 色:通讯作者

Role:Corresponding author

邮 箱:1535686840@qq.com

作者简介:崔军,女,工程师,E-mail:1535686840@qq.com。

刘子利

机 构:南京航空航天大学材料科学与技术学院,南京,211106

Affiliation:College of Materials Science and Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing, 211106,China

刘希琴

机 构:南京航空航天大学材料科学与技术学院,南京,211106

Affiliation:College of Materials Science and Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing, 211106,China

王怀涛

机 构:南京航空航天大学材料科学与技术学院,南京,211106

Affiliation:College of Materials Science and Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing, 211106,China

胥橙庭

角 色:中文编辑

Role:Editor

AlloyAlMnZn
15Bal.
250.1Bal.
350.2Bal.
450.3Bal.
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F001.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F002.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F003.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F004.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F005.jpg
Alloy

bc/(mV·

decade-1)

ba/(mV·

decade-1)

Icorr/(μA·cm-2)
Zn-5Al56346.4
Zn-5Al-0.1Mn43274.2
Zn-5Al-0.2Mn27181.4
Zn-5Al-0.3Mn32233.2
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F006.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F007.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F008.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F009.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F010.jpg
html/njhkht/201901018/alternativeImage/e4ae91b6-010b-4359-bfb7-12b1482a2658-F011.jpg

表1 Zn-Al合金的名义成分(质量分数)(%)

Tab.1 Nominal composition of Zn-Al alloy (in mass)(%)

图1 铸态Zn-5Al-xMn的显微组织

Fig.1 Metallographic structure of cast Zn-5Al-xMn alloys

图2 铸态Zn-5Al-0.3Mn合金的SEM像和EDS谱

Fig.2 SEM image and EDS patterns of cast Zn-5Al-0.3Mn alloy

图3 Zn-5Al-xMn合金的腐蚀速率

Fig.3 Corrosion rate of Zn-5Al-xMn alloys

图4 Zn-5Al-xMn合金在3.5%NaCl中性水溶液中自腐蚀电位与浸泡时间的关系曲线

Fig.4 Relationship between the corrosion potential Ecorr and the exposure time in 3.5% NaCl solution

图5 Zn-5Al-xMn合金在3.5%NaCl溶液中的极化曲线

Fig.5 Polarization curves of Zn-5Al-xMn alloys in 3.5% NaCl solution

表2 极化曲线拟合所得的ba, bcIcorr

Tab.2 Values of Icorr, ba and bc, deduced from polariza-tion measurements

图6 在3.5%NaCl溶液中浸泡不同时间的Zn-5Al-xMn合金Nyquist图

Fig.6 Nyquist diagrams of Zn-5Al-xMn under different exposure times in 3.5% NaCl solution

图7 Zn-5Al-xMn合金电化学阻抗谱数据拟合建立的等效电路

Fig.7 Equivalent circuit for fitting the EIS data of Zn-5Al-xMn alloys

图8 Zn-5Al-xMn合金在3.5%NaCl溶液中RH随浸泡时间的变化

Fig.8 Variation of the resistance RH as a function of immersing time for Zn-5Al-xMn alloys in 3.5% NaCl solution

图9 Zn-5Al-xMn合金在3.5%NaCl溶液中Y0随浸泡时间的变化

Fig.9 Variation of Y0 as a function of immersing time for Zn-5Al-xMn in 3.5% NaCl solution

图10 实验合金在3.5%NaCl溶液中静置不同时间后的腐蚀显微组织

Fig.10 Corrosion morphology of experimental alloys etching in 3.5% NaCl solution

图11 Zn-5Al-xMn合金在中性3.5%NaCl溶液中浸泡480 h后SEM腐蚀形貌

Fig.11 SEM morphology of Zn-5Al-xMn alloys after 480 h exposure in 3.5% NaCl solution

image /

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根据Zn-5Al-xMn合金腐蚀过程特点,对其电化学阻抗谱数据进行拟合,建立了等效电路模型RsQRtZWRl))(图7)。常相位角元件Q=[Y·(n]-1,其中Y为表征Q的导纳,Ω-1·cm-2·s-nj=(-1)1/2ω是角频率;n是与电极表面粗糙度相关的量纲一指数,n值在实验中范围为0.7~0.8[11]Rs为饱和甘汞电极参比电极的鲁金毛细管口到工作电极间的溶液电阻,R1为发生阴极去极化反应时的电荷转移电阻,Rt为发生阳极溶解反应Zn+2OH- → Zn(OH)2+2e-时的电荷转移电阻,ZW为Warburg阻[12]

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  • 参考文献

    • 1

      刘子利, 刘希琴, 王怀涛, 等.Ti 对Zn-5Al 合金组织及耐腐蚀性能的影响[J].中国腐蚀与防护学报,2014,34(6):515-522.

      LIU Zili, LIU Xiqin, WANG Huaitao, et al. Effect of Ti addition on microstructure and corrosion property of Zn-5Al alloy[J]. Journal of Chinese Society Corro-sion Protection, 2014,34(6):515-522.

    • 2

      ROSALBINO F, ANGELINI E, MACCIO D, et al. Application of EIS to assess the effect of rare earths small addition on the corrosion behaviour of Zn-5%Al (Galfan) alloy in neutral aerated sodium chloride solution[J]. Electrochimica Acta, 2009, 54(4):1204-1209.

    • 3

      王先德, 王建华, 苏旭平, 等. 锰对ZZnAl4Y锌合金显微组织和力学性能的影响[J]. 铸造, 2010, 59 (3):312-314.

      WANG Xiande, WANG Jianhua, SU Xuping, et al. Effect of manganese on microstructure and mechanical properties of ZZnAl4Y zinc alloy[J].Foundry,2010,59(3):312-314.

    • 4

      LI Y Y, LUO J M, LUO Z Q, et al. The microstructure and wear mechanism of a novel high-strength, wear-resistant zinc alloy (ZMJ)[J]. J Mater Process Tech, 1995, 55(3/4):154-161.

    • 5

      MUNZ R, WOLF G K, GUZMAN L, et al. Zinc/manganese multilayer coatings for corrosion protection[J]. Thin Solid Films, 2004, 459(1/2):297-302.

    • 6

      ZHANG B, ZHOU H B, HAN E H, et al. Effects of a small addition of Mn on the corrosion behaviour of Zn in a mixed solution[J]. Electrochimica Acta, 2009, 54(26):6598-6608.

    • 7

      SHI Z, LIU M, ATRENS A. Measurement of the corrosion rate of magnesium alloys using Tafel extrapolation[J]. Corrosion Science, 2010, 52(2): 579-588.

    • 8

      曹楚南. 腐蚀电化学原理[M]. 北京: 化学工业出版社, 2004.

      CAO Chunan. Corrosion theory[M]. Beijing: Chemical Industry Press, 2004.

    • 9

      SOUTO R M, FERNANDEZ M L, GONZALEZ S, et al. Comparative EIS study of different Zn-based intermediate metallic layers in coil-coated steels[J]. Corrosion Science, 2006, 48(5): 1182-1192.

    • 10

      孙敏, 肖葵, 董超芳, 等. 带腐蚀产物超强度钢的电化学行为[J]. 金属学报, 2011, 47(4):442-448.

      SUN Min, XIAO Kui, DONG Chaofang, et al. Elec-trochemical behaviors of ultra high strength steels with corrosion products[J]. Acta Metallurgica Sinica, 2011, 47(4):442-448.

    • 11

      HAMLAOUI Y, PEDRAZA F, TIFOUTI L. Corrosion monitoring of galvanized coatings through electrochemical impedance spectroscopy[J]. Corrosion Science, 2008, 50(6):1558-1566.

    • 12

      李党国, 冯耀荣, 白真权, 等. 温度对N80碳钢CO2腐蚀产物膜性能的影响[J]. 中国腐蚀与防护学报, 2008, 28(6):369-373.

      LI Dangguo, FENG Yaorong, BAI Zhenquan, et al. Effect of temperature on properties of CO2 corrosion scale of N80 carbon steel[J]. Journal of Chinese Society Corrosion Protection, 2008, 28(6):369-373.

    • 13

      陈长风, 路民旭, 赵国仙, 等. 腐蚀产物膜覆盖条件下油套管钢CO2腐蚀电化学特征[J]. 中国腐蚀与防护学报, 2003, 23(3):139-143.

      CHEN Changfeng, LU Minxu, ZHAO Guoxian, et al. Electrochemical characteristics of CO2 corrosion of well tube steels with corrosion scales[J]. Journal of Chinese Society Corrosion Protection, 2003,23(3):139-143.

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