成膜温度对镁合金镧盐转化膜耐蚀性的影响  

Effects of Film Forming Temperature on Corrosion Resistance of Lanthanum Salt Conversion Film on Magnesium Alloys

作　　者：许满足 邹忠利[1] XU Man-zu;ZOU Zhong-li(School of Materials Science and Engineering,North Minzu University,Yinchuan 750021,China)

机构地区：[1]北方民族大学材料科学与工程学院,宁夏银川750021

出　　处：《材料保护》2021年第4期90-93,117,共5页Materials Protection

基　　金：2019年度北方民族大学校级重点项目(2019KJ10);2020年度宁夏回族自治区自然科学基金项目(2020AAC03193)资助。

摘　　要：为了探究镁合金表面单纯镧盐转化膜的最佳成膜温度,采用不同成膜温度在镁合金表面制备了镧盐转化膜,利用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)对膜层表面形貌及成分组成进行观察分析,采用点滴试验和电化学方法对膜层耐蚀性能进行了探究。结果表明:镁合金试样表面生成了镧盐转化膜,不同成膜温度所得试样的表面存在大小不一的裂纹,其中20℃获得的镧盐转化膜表面裂纹最少;EDS结果表明镁合金表面形成的镧盐转化膜主要组成为La和O元素,XRD结果表明转化膜主要组成是氢氧化镧;点滴试验结果显示20℃获得的镧盐转化膜耐蚀效果最好,电化学测试结果与点滴试验结果存在一致性,相对未处理镁合金试样,自腐蚀电位正移了865 mV,自腐蚀电流密度下降了4个数量级,阻抗模量增加了约4个数量级。In order to find out the best film forming temperature of pure lanthanum salt conversion film on the surface of magnesium alloy,lanthanum salt conversion film was prepared on the surface of magnesium alloy at different film forming temperatures.Scanning electron microscopy(SEM),energy dispersive x-ray spectrometer(EDS)and X-ray diffraction(XRD)were used to observe and analyze the surface morphology and composition of the film,the corrosion resistance of the coating was studied by drop test and electrochemical method.Results showed that lanthanum salt conversion film was formed on the surface of magnesium alloy,and there were cracks with different sizes on the surface of the samples under the different film forming temperatures,among which the surface cracks of lanthanum salt conversion film obtained at 20℃were the least;EDS results showed that the lanthanum salt conversion film on the surface of magnesium alloy was mainly composed of La and O elements,XRD results showed that lanthanum hydroxide was the main component of the conversion film;The results of drop experiment showed that the lanthanum salt conversion film obtained at 20℃had the best corrosion resistance,and the electrochemical test results were consistent with the drop experiment results.Compared with the untreated magnesium alloy samples,the self-corrosion potential shifted 865 mV positively,the self-corrosion current density was decreased by 4 orders of magnitude,and the impedance modulus was increased by about 4 orders of magnitude.

关 键 词：硝酸镧 化学转化膜 成膜温度 镁合金 耐蚀性 

分 类 号：TG147.45[一般工业技术—材料科学与工程]