摘要
目的评价2A12铝合金不同阳极氧化膜在氯离子作用下的腐蚀电化学演变行为。方法以2A12铝合金为基材,分别制备重铬酸盐封闭硫酸阳极氧化(DS-SAA)膜、热水封闭硫酸阳极氧化(HWS-SAA)膜和稀铬酸封闭铬酸阳极氧化(DCS-CAA)膜,采用动电位极化、电化学交流阻抗表征及拟合,并结合体视显微镜等方法,分析不同氧化膜试件的电化学参数在质量分数为3.5%的NaCl溶液中随浸泡时间的变化,对膜层演变规律及机理进行讨论。结果硫酸阳极氧化和铬酸阳极氧化膜的厚度分别约为8μm和3μm,后者表面缺陷更少。在NaCl溶液中浸泡1 h后,DS-SAA、HWS-SAA和DCS-CAA试件的自腐蚀电流密度分别为9.1、0.86、12.9 nA/cm^2,经168 h浸泡后,分别增大为15.5、35.3、2628 nA/cm^2,DS-SAA试件的自腐蚀电位升高了205 mV,DCS-CAA试件的自腐蚀电位从-604 mV降低到-930 mV。随着浸泡时间的延长,DS-SAA试件的Rb和Rp值始终分别高于107Ω·cm^2和105Ω·cm^2。浸泡24 h后,HWS-SAA和DCS-CAA试件的阻抗谱中开始出现韦伯阻抗,Rb和Rp值迅速下降。结论三种氧化膜在浸泡初期的耐蚀性能相当,随着时间的延长,重铬酸盐封闭硫酸阳极氧化膜具有较高的耐蚀性和耐久性,其余两种氧化膜的耐蚀性能则快速下降,168 h后多孔层几乎完全失效。氧化膜耐蚀性能的差异与膜厚和封闭机理有关。
The work aims to evaluate the corrosion electrochemical evolution behavior of 2A12 aluminum alloy with different anodic films under the action of chloride ions.The dichromate sealed sulfuric acid anodizing(DS-SAA)film,hot water sealed sulfuric acid anodizing(HWS-SAA)film and dilute chromic acid sealed chromic acid anodizing(DCS-CAA)film were prepared on 2A12 aluminum alloy.Potentiodynamic polarization and electrochemical impedance characterization and fitting,combined with stereoscopic microscope,were used to analyze the change of electrochemical parameters of different oxide film samples with immersion time in 3.5%NaCl solution and discuss the evolution law and mechanism of film layer.The thickness of SAA film and CAA film was about 8μm and 3μm respectively,and the surface defects of the latter were less.After immersion in NaCl solution for 1 hour,the corrosion current density of DS-SAA,HWS-SAA,and DCS-CAA samples were 9.1,0.86 and 12.9 nA/cm^2,respectively.After 168 hours of immersion,the corrosion current density of DS-SAA,HWS-SAA,and DCS-CAA samples increased to 15.5,35.3 and 2628 nA/cm^2,respectively.The corrosion potential of DS-SAA samples increased by 205 mV,and that of DCS-CAA samples decreased from-604 mV to-930 mV.With the increase of immersion time,the Rb and Rp values of DS-SAA were higher than 107 and 105Ω·cm^2.After immersion for 24 hours,Warburg impedance appeared in impedance spectra of HWS-SAA and DCS-CAA specimens,and Rb and Rp values decreased rapidly.The corrosion resistance of the three kinds of oxide films is equal at the initial stage of immersion.With the extension of time,the dichromate sealed sulfuric acid anodizing(DS-SAA)film has higher corrosion resistance and durability,while the corrosion resistance of the other two kinds of oxide films decreases rapidly,and the porous layer almost completely fails after 168 hours.The difference of corrosion resistance of anodic film is related to film thickness and sealing mechanism.
作者
陈跃良
张杨广
卞贵学
张勇
张柱柱
CHEN Yue-liang;ZHANG Yang-guang;BIAN Gui-xue;ZHANG Yong;ZHANG Zhu-zhu(Naval Aviation University Qingdao Campus,Qingdao 266041,China;The 32102 Unit of PLA,Yantai 265200,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2020年第9期348-356,共9页
Surface Technology
