Ni-Co-Zn三元合金的共沉积行为及耐蚀机制  

Codeposition Behaviors and Anti-Corrosive Mechanism of Ni-Co-Zn Ternary Alloys

作　　者：周小卫[1] 荆雪艳 傅瑞雪 王宇鑫[1] ZHOU Xiaowei;JING Xueyan;FU Ruixue;WANG Yuxin(School of Materials Science and Engineering,Jiangsu University of Science and Technology,Zhenjiang 212003,China)

机构地区：[1]江苏科技大学材料科学与工程学院,镇江212003

出　　处：《金属学报》2024年第11期1499-1511,共13页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.51605203。

摘　　要：鉴于电沉积Ni-Co-Zn三元合金中Zn^(2+)与Ni^(2+)、Co^(2+)标准还原电势差异大,优先析出的Zn会吸附在电极表面并形成Zn(OH)2沉淀膜,阻碍后续Ni^(2+)和Co^(2+)还原放电,不利于合金共沉积,本工作以抗坏血酸(H_(2)Asc)作为络合剂,通过调控镀液中Ni^(2+)∶Co^(2+)∶Zn^(2+)摩尔浓度比,旨在实现Ni-Co-Zn三元共沉积。利用SEM、XRD等方法分析了离子摩尔浓度比和H_(2)Asc浓度对电沉积Ni-Co-Zn合金表面形貌和织构生长的影响。结果表明,当Ni^(2+)∶Co^(2+)∶Zn^(2+)摩尔浓度比为4∶5∶1时,合金镀层中Ni含量高达12.2%(质量分数),晶粒细化致密。当H_(2)Asc浓度为5 g/L时,织构生长呈类菜花球状,晶粒尺寸约为300 nm,具有最小的生长应力9.04 MPa。镀层中Zn含量随H_(2)Asc浓度增加而显著降低,而Ni+Co含量则逐渐上升,这主要归因于镀液中Zn^(2+)与HAsc^(-)络合成了配位化合物[ZnHAsc]^(+)并抑制了Zn的择优生长,留给Ni或Co更多的活性位点。合金中存在γ-Ni_(5)Zn_(21)、CoZn_(13)和Ni_(3)Zn_(22)等金属间化合物,说明适量H_(2)Asc的加入有助于实现合金共沉积。添加H_(2)Asc后试样的自腐蚀电位(E_(corr))均大幅正移,降低了腐蚀驱动力;当H_(2)Asc添加量为5 g/L时,显示出最佳的耐腐蚀性能,其中E_(corr)正移了约200 mV,自腐蚀电流较未添加时降低了约75%。添加H_(2)Asc后试样的电化学阻抗谱(EIS)均由大半径的容抗弧和感抗弧组成,这是由于合金镀层中存在γ-Ni_(5)Zn_(21)相以及浸泡过程中形成的[Zn(OH)_(4)]^(2-)胶质微溶腐蚀产物,通过絮凝作用沉淀下来并包覆在活性Zn溶解后的活性表面,减少Cl-向镀层内部扩散渗透的渠道,提高了其抗腐蚀性能。Zinc-metal alloys with ferrous group metals such as Ni,Co,and Fe have been used for industrial applications due to their better corrosion performance compared to pure Zn.Among them,ternary Zn-Ni-Co alloys,which have superior corrosion resistance and magnetic features,have attracted extensive attention,and have been used as functional films in electro-mechanical system(EMS)devices and magnetic recording media.However,large differences in the reduction peak potential between Zn^(2+),Ni^(2+),and Co^(2+)restrict their codeposition because Zn-competitive adsorption hinders the discharge transfer of Ni^(2+)or Co^(2+).In view of the aforementioned statements,the effects of molar concentration ratios of Ni^(2+):Co^(2+):Zn^(2+)and the ascorbic acid(H_(2)Asc)concentrations in the bath on the surface features and textures of the Zn-Ni-Co alloys were assessed and characterized using FE-SEM,XRD,etc.Results showed that under the optimized condition of Ni^(2+):Co^(2+):Zn^(2+)=4:5:1,the Ni content in the Ni-Co-Zn deposits reached 12.2%,which was instrumental in grain refinement.From the cyclic voltammetry curves,the potential of the reduction peak positively shifted from−1.47 V to−1.28 V,validating better codeposition with an appropriate H_(2)Asc concentration.SEM observations depicted a cauliflower-like texture with a crystal size of~300 nm at a minimum growing stress of 9.04 MPa for the samples with 5 g/L H_(2)Asc concentration.From EDS analysis,with increasing H_(2)Asc concentration from 1 g/L to 5 g/L,the Ni+Co content in the Ni-Co-Zn deposits gradually increased but their Zn content decreased,which was attributed to the addition of H_(2)Asc in the form of[ZnHAsc]^(+)to offer more active sites for Ni or Co growth.Intermetallic compounds such asγ-Ni_(5)Zn_(21),CoZn_(13),and Ni_(3)Zn_(22)were determined using XRD.The anticorrosive behavior was evaluated via potentiodynamic polarization(Tafel)tests in a 3.5%NaCl solution.The free corrosion potential(E_(corr))positively shifted by~200 mV for the samples with 5 g/L H_(2)Asc

关 键 词：Ni-Co-Zn三元合金 异常共沉积 H_(2)Asc络合剂 耐腐蚀性 

分 类 号：TB332[一般工业技术—材料科学与工程]