Er(NO_(3))_(3)掺杂对镁合金微弧氧化涂层形貌和耐蚀性能的影响

Effect of Er(NO_(3))_(3)Doping on Morphology and Corrosion Resistance of Microarc Oxidation Coatings on Magnesium Alloys

通过微弧氧化技术对镁合金表面改性,旨在获得拥有优良抗腐蚀性的陶瓷涂层。在硅酸盐电解液体系下对AZ31镁合金进行微弧氧化处理,研究Er(NO_(3))_(3)掺杂量变化对改性涂层相组成、微观结构、表面粗糙度、润湿角以及电化学性能的影响。结果表明,在电解液中掺杂和未掺杂稀土盐Er(NO_(3))_(3),获得的镁合金涂层均由MgO、MgSiO_(3)和Mg_(2)SiO_(4)等晶相组成,未检测到Er的氧化物相。掺杂稀土盐Er(NO_(3))_(3)后涂层中的MgSiO3相含量有所增加。未掺杂Er(NO_(3))_(3)时,涂层具有火山口状的微孔结构。随着Er(NO_(3))_(3)掺杂量增加,涂层表面的微孔数量呈现出先增加后降低的趋势。当Er(NO_(3))_(3)掺杂量超过4‰时,微弧氧化涂层微孔尺寸明显减小,出现较大区域的裂纹分布表面。在不同Er(NO_(3))_(3)掺杂量后获得涂层表面粗糙度在1.6~2.1μm。在电解液中引入Er(NO_(3))_(3)后,涂层腐蚀电位正向移动。与未添加Er(NO_(3))_(3)试样相比,掺杂Er(NO_(3))_(3)后获得的涂层腐蚀电流降低约1个数量级,涂层耐蚀性略有提高。

The surface of magnesium alloys was modified by micro-arc oxidation technology in order to obtain a ceramic coating with excellent corrosion resistance.The effect of Er(NO_(3))_(3)doping on the phase composition,microstructure,surface roughness,wetting angle and electrochemical properties of AZ31 magnesium alloy was investigated by micro-arc oxidation treatment in silicate electrolyte system.The results showed that the magnesium alloy coatings obtained by doping and undoping the rare earth salt Er(NO_(3))_(3)in the electrolyte were all composed of MgO,MgSiO_(3)and Mg_(2)SiO_(4)crystal phases,and oxide phase of Er was not detected.The MgSiO3 phase content in the coating increased after doping Er(NO_(3))_(3).Without doping Er(NO_(3))_(3),the coating had a crater-like microporous structure.With the increase of Er(NO_(3))_(3)doping amount,the number of micropores on the coating surface firstly increased and then decreased.When the doping amount of Er(NO_(3))_(3)was more than 4‰,the micropore size of micro-arc oxidation coating decreased obviously and a large area of crack surface appeared.The surface roughness of the coating varies from 1.6μm to 2.1μm with different Er(NO_(3))_(3)doping amount.When Er(NO_(3))_(3)was introduced into the electrolyte,the corrosion potential of the coating moved forward positive potential.Compared with the specimen without doping Er(NO_(3))_(3),the corrosion current of the coating obtained by doping Er(NO_(3))_(3)decreased by about one order of magnitude,so the corrosion resistance of the coating was slightly improved.