石墨烯浓度对镁基陶瓷膜生长及耐蚀性的影响

Effect of Graphene Concentration on Growth and Corrosion Resistance of Magnesium Based Ceramic Coating

目的研究石墨烯浓度对AZ91D镁合金微弧氧化陶瓷膜生长及耐蚀性的影响。方法通过超声分散获得石墨烯分散液,添加到锆盐体系电解液中,采用微弧氧化技术,在AZ91D镁合金表面制备微弧氧化陶瓷膜。采用SEM、EDS对陶瓷膜微观结构进行分析,采用XRD对陶瓷膜物相组成进行分析,采用电化学工作站测量陶瓷膜在3.5%NaCl溶液中的极化曲线,并对其耐蚀性进行分析。结果随着石墨烯浓度增加,陶瓷膜微孔中的C含量先增加后减小,微孔外的C含量增加,陶瓷膜表面孔径和粗糙度先减小后增加,孔隙率增加,厚度几乎没有变化。并且石墨烯浓度对陶瓷膜相成分没有影响,主要相组成为MgF2、ZrO2、MgO和Mg2Zr5O12。与未添加石墨烯的试样相比,添加石墨烯后,腐蚀电流密度降低了1~2个数量级,极化电阻增加了1~2个数量级。在石墨烯质量浓度为0.15g/L时,陶瓷膜表面微孔孔径达到最小,腐蚀电流密度最小,为9.46×10^-7A/cm^2,极化电阻最大,为1.95×10^6W·cm^2,耐蚀性最好。结论一定浓度石墨烯能够减小微弧氧化陶瓷膜微孔孔径,增加孔隙率,提高陶瓷膜的耐蚀性。

The work aims to study the effect of graphene concentration on the growth and corrosion resistance of micro-arc oxidation ceramic coating of AZ91D magnesium alloy. Graphene dispersion was obtained by ultrasonic dispersion and added to the zirconium salt electrolyte to prepare the micro-arc oxidation ceramic coating on the surface of the magnesium alloy by micro-arc oxidation technique. The microstructure of the ceramic coating was analyzed by SEM and EDS, and the phase composition of the ceramic coating was analyzed by XRD. The polarization curves of the ceramic coating in 3.5%NaCl solution were measured by electrochemical workstation, and the corrosion resistance was analyzed. With increasing graphene concentration, the C content in the micropores of the ceramic coating firstly increased and then decreased, and the C content outside the micropores increased. The pore diameter of the ceramic coating and surface roughness decreased firstly and then increased. The porosity increased, but the thickness hardly changed. Moreover, the concentration of graphene had no effect on the phase composition of the ceramic coating, and the main phase composition was MgF2, ZrO2, MgO and Mg2Zr5O12. Compared with the sample without graphene, the corrosion current density was reduced by 1~2 orders of magnitude and the polarization resistance was increased by 1~2 orders of magnitude. When the concentration of graphene was 0.15 g/L, the pore diameter of the ceramic coating was the smallest, the corrosion current density was the smallest of 9.46×10^-7 A/cm^2, and the polarization resistance was the largest of 1.95×10^6 W·cm^2. Thus, the coating had the best corrosion resistance. A certain concentration of graphene can reduce the micropore diameter of micro-arc oxidation ceramic coating, increase the porosity of ceramic coating and improve the corrosion resistance of ceramic coating.