次磷酸钠对锌-镍合金电沉积和镀层耐蚀性的影响  

Effect of sodium hypophosphite on electrodeposition behavior and corrosion resistance of Zn-Ni alloy coating

作　　者：刘军松 潘秀 田驰 LIU Junsong;PAN Xiu;TIAN Chi(China Zhenhua Group Yunke Electronic Co.,Ltd.,Guiyang 550018,China)

机构地区：[1]中国振华集团云科电子有限公司,贵州贵阳550018

出　　处：《电镀与涂饰》2022年第2期77-84,共8页Electroplating & Finishing

摘　　要：在乙酸盐−铵盐体系电镀锌–镍合金镀液配方中添加次磷酸钠,以45钢为基体电沉积锌–镍–磷合金。通过循环伏安法和小槽电镀实验研究了pH、温度和电流密度对镀层成分的影响,采用扫描电镜、能谱、X射线荧光、X射线衍射等技术对镀层形貌和微观组织进行表征,采用Tafel极化曲线和电化学阻抗谱对镀层的耐蚀性进行测试。结果表明:在不含主盐的基础镀液中,次磷酸钠的P不能被还原出来,而次磷酸钠与Zn^(2+)、Ni^(2+)共存时有助于Ni的沉积,对Zn的沉积无明显影响;温度升高则镀层中Zn减少,Ni和P增多;降低pH有利于锌–镍共沉积;镀层的P含量随电流密度增大而减少。P元素的掺入能完全消除锌−镍合金的裂纹,细化镀层晶粒。低P含量(P质量分数低于1%)的锌–镍–磷合金镀层具有比高P含量(P质量分数大于10%)的镀层更好的耐蚀性。Sodium hypophosphite was added to a Zn–Ni alloy plating solution comprising acetate and ammonium salt for electroplating to prepare a Zn–Ni–P alloy coating on 45 steel.The effects of pH,temperature,and current density on elemental composition of the coating were studied by cyclic voltammetry and small-tank electroplating experiment.The morphology and microstructure of the coating were characterized by scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS),X-ray fluorescence(XRF)spectrometry,and X-ray diffraction(XRD).Tafel polarization curve measurement and electrochemical impedance spectroscopy were used to test the corrosion resistance of the coating.The results showed that the element P of sodium hypophosphite in the base solution without nickel and zinc salts could not be reduced.The presence of sodium hypophosphite in a solution containing Zn^(2+)and Ni^(2+)facilitates to the deposition of Ni,but has no obvious effect on the deposition of Zn.When the temperature is raised,the content of Zn in the coating is decreased and the contents of Ni and P are increased.The decrease of pH is beneficial to the codeposition of zinc and nickel.The contents of P in the coating is decreased with the increasing of current density.The incorporation of P eliminates the cracking of Zn–Ni alloy and refines its grains.The Zn–Ni–P alloy coating with low P content(mass fraction of P less than 1%)has better corrosion resistance than that with high P content(mass fraction of P more than 10%).

关 键 词：锌–镍–磷合金 电沉积 次磷酸钠 耐蚀性 电化学 磷含量 

分 类 号：TU512.2[建筑科学—建筑技术科学]