石墨烯对无铬达克罗涂层耐蚀性能影响  

Effect of Graphene on Corrosion Resistance of Chromium-free Dacromet Coatings

作　　者：蔡家斌[1] 肖齐洪 杨绿[1] CAI Jiabin;XIAO Qihong;YANG Lv(School of Mechanical Engineering,Guizhou University,Guiyang 550025,China)

机构地区：[1]贵州大学机械工程学院

出　　处：《腐蚀科学与防护技术》2019年第6期565-575,共11页Corrosion Science and Protection Technology

基　　金：贵州省科技计划项目(黔科合LH字[2017]7245号);贵州省科技支撑计划项目(黔科合支撑[2018]2168)~~

摘　　要：针对无铬达克罗防腐性能较差的问题,向涂液中添加不同含量石墨烯制备复合涂层以期提升涂层的耐蚀性能。实验采用硝酸铵快速腐蚀实验、浸泡实验、中性盐雾实验测试了涂层的耐蚀性能,利用SEM、EDS、XRD、Raman等方法观察分析了涂层腐蚀前后的组织形貌以及成分变化,明确了石墨烯在无铬达克罗涂层中的形貌与状态,并结合电化学实验,测试了4种涂层在模拟海水(3.5%(质量分数)NaCl溶液)中的Tafel极化曲线以及电化学阻抗谱,对其结果进行比较且应用相应的等效电路分析了其提高防腐性能的机理。结果表明:在腐蚀过程中Zn最先被消耗,Al与其他物质发生化学反应生成难溶于水的致密腐蚀产物;石墨烯以片状的结构嵌在锌铝粉之间,与片状锌铝粉相互交叠、保持平行,增加了涂层的致密性;加入少量石墨烯能够使无铬达克罗涂层的自腐蚀电位升高,腐蚀电流密度降低;涂层Nyquist低频半径和Bode幅值在同一时间段内的最大值均为0.12%石墨烯增强涂层,耐盐雾能力最佳。石墨烯加强了无铬达克罗涂层机械的壁垒保护作用,延缓了电解质溶液渗入的进程。Composite coatings based on Cr-free Dacromet coating with addition of different amount of graphene were prepared aiming to increase the corrosion resistance of Cr-free Dacromet coating.The corrosion performance of the coatings was assessed via ammonium nitrate rapid corrosion test,immersion test and salt spray test.The state of graphene in composite coatings was characterized by means of SEM,EDS,XRD and Raman spectroscope.While the electrochemical behavior of coatings in artificial seawater(3.5%(mass fraction)NaCl solution)was comparatively examined via open-circuit potential measurement and Tafel polarization curve and electrochemical impedance spectroscopy,and the corrosion mechanism was analyzed with the corresponding equivalent circuits.The results show that:(1)Zn is first consumed in the corrosion process,and Al reacts with other substances to form dense corrosion products,which are insoluble in water;(2)graphene as sheet-like structure is embedded between Znand Al-powder,which is overlapping and paralleling with Zn flake and Al powder,thereby,increases the compactness of coatings;(3)a small amount of graphene can increase the corrosion potential and decrease the corrosion current density of Cr-free Dacromet coating,and accordingly;(4)the capacitive arc radius and impedance of the composite coatings reached the maximum when the graphene content was 0.12%,and the salt spray resistance of the coatings was the best.In conclusion,the graphene can strengthen the barrier effect of Cr-free Dacromet coatings and delay the inward migration process of the corrosive species from the electrolyte.

关 键 词：无铬达克罗 石墨烯 耐蚀性 电化学 

分 类 号：TG174.44[金属学及工艺—金属表面处理]