镁合金达克罗涂层的制备及性能研究
发布时间：2018-10-12 09:42
【摘要】：作为最轻的金属结构材料,镁合金材料具有比强度、比刚度高,电磁屏蔽性能好等一系列优点,这些优异的特性使其在汽车工业、航空航天、电子制造业、通讯行业等领域也得到越来越广泛的使用,但镁合金较差的耐蚀性能影响其应用发展。达克罗涂层作为一种广泛应用于钢铁材料的绿色清洁型表面处理技术,然而当达克罗技术应用于镁合金时,由于镁合金化学活性高,在成膜过程中达克罗涂液中的酸性物质优先与镁反应生成疏松的腐蚀物,不能形成致密的阻挡层。本文采用扫描电镜(SEM)及能谱仪(EDS)、X射线衍射仪(XRD)、极化曲线测试及电化学阻抗谱、浸泡实验、盐雾试验等多种分析测试手段,以AZ31镁合金板材为实验材料,在优化镁合金达克罗涂层成分配比的基础上,研究了不同硼酸含量对达克罗膜层成分、组织形态结构及耐蚀性能的影响,并制备了硅烷-达克罗复合涂层以进一步提高其耐腐蚀性能,得到的主要结论为:镁合金达克罗涂层优化成分配比为:片状锌粉的含量为300g/L,铬酐含量为80g/L;乙二醇含量为180ml/L。增稠剂为羟乙基纤维素;p H值调节剂为Zn O;消泡剂为异辛醇。最佳的固化工艺为80℃保温10min,升温至300℃固化30min。制备的镁合金达克罗涂层主要由Zn、Mg及其铬酸化合物Mg Cr O_4和氧化物Zn O、Mg O、Cr_2O_3、Cr O_3组成。涂层厚度在10μm左右。添加硼酸取代部分铬酸后,涂层中出现硼的氧化物B_2O_3,随着硼酸含量的增加,Mg、Mg Cr O_4含量降低,Cr_2O_3及Cr O_3的含量先上升后降低,在添加2%硼酸时含量最高;此时涂层表面裂纹孔洞的数量最少,涂层致密性最好。随着硼酸含量的增加使涂层腐蚀电位降低,自腐蚀电流密度先减小后增大,硼酸含量为2%时腐蚀电流密度最小,比未添加硼酸时降低一个数量级。同时,涂层的电荷转移电阻值R_(ct)先升高后降低,含量为2%时达到最大值。添加2%硼酸涂层盐雾腐蚀75h时出现明显的腐蚀现象。在达克罗涂层上二次涂覆硅烷涂料制备了硅烷-达克罗复合涂层。涂层中出现Si O_2和Zn_2Si O_4新相。复合涂层结合紧密,厚度在20μm左右。与达克罗涂层相比,复合涂层极化电阻R_p值由208.1Ω·cm~2提高到770.3Ω·cm~2,腐蚀电流密度I_(corr)大小由5.068×10~(-5)A·cm~(-2)减小至2.716×10~(-6)A·cm~(-2),电荷转移电阻R_(ct)由107.5Ω·cm~2提高到217.2Ω·cm~2。与硼酸取代部分铬酸的达克罗涂层相比,复合涂层的耐盐雾腐蚀性显著增强。
[Abstract]:As the lightest metal structure material, magnesium alloy material has a series of advantages, such as specific strength, high specific stiffness, good electromagnetic shielding performance and so on. Communication industry and other fields have been more and more widely used, but the poor corrosion resistance of magnesium alloy affects the development of its application. Dacromet coating is a kind of green clean surface treatment technology widely used in iron and steel materials. However, when Dacromet technology is applied to magnesium alloy, the chemical activity of magnesium alloy is high. In the process of film formation, the acidic substance in the Dacromet solution preferentially reacts with magnesium to form a loose corrosion substance, which can not form a dense barrier layer. In this paper, (SEM) and (EDS), X ray diffractometer of scanning electron microscope (SEM) and (EDS), X ray diffractometer (EDS), X) were used to measure the polarization curve and electrochemical impedance spectrum (EIS), immersion test, salt spray test and so on. The AZ31 magnesium alloy sheet was used as the experimental material. The effects of different boric acid content on the composition, microstructure and corrosion resistance of Dacromet coating on magnesium alloy were studied. Silane-Dacromet composite coating was prepared to further improve its corrosion resistance. The main conclusions are as follows: the optimum composition of the coating is: the content of zinc powder is 300 g / L, the content of chromium anhydride is 80 g / L, and the content of ethylene glycol is 180 ml / L. The thickener is hydroxyethyl cellulose; p H value regulator Zn O, and the defoamer is isooctanol. The optimum curing process is 80 鈩，
本文编号：2265661
[Abstract]:As the lightest metal structure material, magnesium alloy material has a series of advantages, such as specific strength, high specific stiffness, good electromagnetic shielding performance and so on. Communication industry and other fields have been more and more widely used, but the poor corrosion resistance of magnesium alloy affects the development of its application. Dacromet coating is a kind of green clean surface treatment technology widely used in iron and steel materials. However, when Dacromet technology is applied to magnesium alloy, the chemical activity of magnesium alloy is high. In the process of film formation, the acidic substance in the Dacromet solution preferentially reacts with magnesium to form a loose corrosion substance, which can not form a dense barrier layer. In this paper, (SEM) and (EDS), X ray diffractometer of scanning electron microscope (SEM) and (EDS), X ray diffractometer (EDS), X) were used to measure the polarization curve and electrochemical impedance spectrum (EIS), immersion test, salt spray test and so on. The AZ31 magnesium alloy sheet was used as the experimental material. The effects of different boric acid content on the composition, microstructure and corrosion resistance of Dacromet coating on magnesium alloy were studied. Silane-Dacromet composite coating was prepared to further improve its corrosion resistance. The main conclusions are as follows: the optimum composition of the coating is: the content of zinc powder is 300 g / L, the content of chromium anhydride is 80 g / L, and the content of ethylene glycol is 180 ml / L. The thickener is hydroxyethyl cellulose; p H value regulator Zn O, and the defoamer is isooctanol. The optimum curing process is 80 鈩，
本文编号：2265661
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