Al 5083表面电泳沉积稀土改性膜制备和表征

CHARACTERIZATION AND CATHODE ELECTROPHORESIS DEPOSITION OF CERIUM MODIFIED FILMS ON Al 5083

采用阴极电泳法在铝合金表面快速沉积Ce改性膜,利用SEM,EDS和XRD研究稀土膜的形貌和结构,用电化学阻抗谱(EIS)和极化曲线方法评价改性铝合金在0.1 mol/L NaCl溶液中的耐蚀性能.结果表明,在0.1 mol/L Ce(NO_3)_3乙醇溶液中用12 V电压阴极电泳60 s后再经热处理获得了厚度约0.8μm的均匀CeO_2膜层.电化学测试结果证实,稀土改性膜对Al 5083基体具有优异的保护性能,试样浸泡31 d未见明显腐蚀,且表面膜层裂纹显著减少,呈现自修复特性.随浸泡时间的增加,电荷转移电阻R_p逐渐增大,表面电容C_t基本不变.

Aluminum alloys are extensively used in many fields such as aeronautics,astronautics, vehicle manufactures and living products due to their good mechanical properties and anti-corrosion performance.Traditionally,the most effective corrosion protection technologies are based on the use of Cr^6＋ containing formulations to extend the applications of aluminum alloys in high corrosive media such as chlorides containing solutions.However,the recent recognition that chromates are highly toxic and carcinogenic has led to extensive research to develop new alternatives.Many works have been published using different conditions to obtain rare earth（RE） conversion layers on several aluminum substrates.Unfortunately,these reported anti-corrosion technologies based on RE modified films presented several drawbacks including long formation time,high formation temperature and even high potential in some cases.The goal of the present work is to introduce the novel cathode electrophoresis technique to quickly deposit cerium modified film on the surface of Al 5083.The morphology and structure of the RE film were characterized by SEM,EDS and XRD,the corrosion resistance was investigated by EIS and potentiodynamic polarization curves in 0.1 mol/L NaCl solution.The results showed that uniform CeO2 film of 0.8μm thickness can be prepared by cathode electrophoresis process in 0.1 mol/L Ce（NO3）3 ethanol solution at a voltage of 12 V for 60 s.Polarization curves confirmed its excellent protective property through inhibiting the cathodic reaction.Impedance data collected from EIS in 0.1 mol/L NaCl solution remained capacitive for 31 d,which indicated the lack of localized corrosion.With the increase of exposure time, the charge-transfer resistance Rp became higher,the surface capacitance Ct nearly kept constant and cracks of the film reduced obviously,demonstrating a self-healing property.Apparently local cathodes were covered during the RE modification processes,thereby reducing the driving force for pitting.