摘要
镁合金耐腐蚀性差,氰化镀和化学镀虽能提高其耐蚀性,但分别存在许多问题,如污染环境、工艺复杂、与镀层结合力差、镀液寿命短等。为此,采用直流(DC)、脉冲电流(PC)方法在AZ31B镁合金表面电沉积锌层,以扫描电子显微镜(SEM)、X射线衍射(XRD)、极化曲线(Tafel)和电化学阻抗谱(EIS)等方法研究了沉积方式对镀层表面形貌、结构和耐蚀性的影响。结果表明:随时间的增加,镀层从初期疏松、多孔,逐渐趋于致密、平整;相同时间下,脉冲镀层更致密、孔隙更少;脉冲方式下晶面衍射峰强度较直流方式有所降低,半峰宽有变大趋势,晶粒有所细化,晶面取向由(101)择优取向变为随机取向;经直流和脉冲电镀锌后,镁合金表面腐蚀电势分别正向移动了0.42V和0.48V,腐蚀电流为80.4μA/cm2和34.57μA/cm2,脉冲条件下制备的镀层耐蚀性较直流制备的镀层有所提高。
Galvanizing coating was prepared on the surface of AZ31B magnesium alloy using direct current(DC)and pulse current(PC),respectively.The effects of power source on the appearance,microstructure,and corrosion resistance of the galvanizing coating were analyzed by means of scanning electron microscopy(SEM)and X-ray diffraction(XRD),and by meas-uring polarization curve(Tafel)and electrochemical impedance spectra(EIS)as well.Results show that the loose and porous coatings in the initial stage were gradually transformed to compact and smooth coatings with extending time.At the same duration,the galvanizing coating prepared with pulse current was more com-pact and contained less porosities than that prepared with direct current.The galvanizing coating prepared with pulse current had a relatively lower intensity of XRD diffraction peaks,an increased half width of peaks,and more fine grains as compared with the same coating prepared with direct current,while the(101)ori-entation of the former was transformed to random orientation of the latter.Moreover,the introduction of DC and PC galvanizing coat-ings on Mg alloy led to positive shift of corrosion potential by 0.42 V and 0.48 V,the corresponding corrosion current density was 80.4 μA/cm and 34.57 μA/cm2,indicating that the PC galvanizing coating had better corrosion resistance than DC galva-nizing coating.
出处
《材料保护》
CAS
CSCD
北大核心
2009年第6期1-3,13,共4页
Materials Protection
基金
吉林省科技发展计划项目(20000513)
关键词
无氰镀锌
脉冲镀锌
直流镀锌
AZ31B镁合金
微观结构
腐蚀性能
cyanide-free galvanizing
pulse current plating
direct current plating
AZ31B magnesium alloy
microstructure
corrosion resistance
