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摘要
In order to study the effect of surface nano-structuring of aluminum alloy on the corrosion performance of MAO coating, ultrasonic cold forging technology (UCFT) was used as a pretreatment to produce a refined layer before a MAO coating was prepared on the surface of 2024 Al alloy (AA2024). The surface roughness was evaluated by atomic force microscope (AFM), and the average surface roughness value of the 5.00 x 5.00 mu m area of UCFT treated sample is 7.477 nm. The grain size of the modified layer were observed by transmission electron microscope (TEM). The result showed that UCFT can refine the grains. The microstructure and phase component of the coated samples were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The observations showed that the micro-pore size of the MAO coating on UCFT treated Al alloy is smaller than that of MAO coating on untreated alloy. The phases of the coated samples with and without UCFT remain the same. The hardness of the samples measured by the micro-hardness tester showed that the UCFT-MAO sample possesses the highest micro-hardness among all the samples. The potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were employed to characterize the corrosion rate and the electrochemical impedance in a 3.5% NaCl solution. For the PDP testing, the sweep rate was 5 mV/s starting from -1.4 V to 0 V, while the EIS tests were carried out in the range of 0.01 Hz-100 kHz with AC voltage amplitude of 10 mV. The PDP and EIS results show that the UCFT-MAO sample has the best corrosion resistance with the lowest corrosion current density, 0.412 A/cm(2). The largest electrochemical impedance is attributed to UCFT pretreatment prior to MAO process on aluminum alloys. The corrosion model of MAO coated AA2024 pretreated by UCFT was proposed.
- 出版日期2016-10-5
- 单位北京石油化工学院; 北京工商大学; 青海民族大学; 中国地质大学（北京）
