AZ31表面含铈疏水涂层制备及腐蚀行为研究

发布时间：2018-05-31 10:07

本文选题：镁合金 + 稀土铈　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：在镁合金表面制备疏水涂层是目前一种研究广泛的防护手段;众多研究表明稀土铈的缓蚀性在镁合金上作用明显。本实验采用阴极电沉积的方法直接在AZ31镁合金表面制备出单一的十四酸钙和十四酸铈以及钙铈混合的疏水涂层,涂层的存在显著提高了镁合金的腐蚀性能。通过研究制备工艺参数(沉积电压和沉积时间)对单一Ca盐(或Ce盐)涂层形态以及腐蚀行为的影响,以及Ca-Ce复合涂层沉积时间比和Ca-Ce摩尔比对Ca-Ce复合涂层的形态及腐蚀行为的影响,发现涂层的制备工艺参数显著影响涂层的形貌及腐蚀性能,但并不影响涂层的物相组成。Ca盐涂层的物相组成为(CH3(CH2)12COO)2Ca,Ce盐涂层的物相是由(CH3(CH2)12COO)4Ce和(CH3(CH2)12COO)3Ce组成的。研究结果表明,沉积电压为50V时,无论是单一Ca盐涂层还是Ce盐涂层,其耐蚀性能最好;对于单一Ca盐涂层,沉积时间越长,其耐蚀性能越优异;对于单一Ce盐涂层,沉积时间60min时的耐蚀性能最好。当在50V电压下沉积60min,且Ca-Ce沉积时间比为2:1,摩尔比为99:1时制得的疏水涂层(即99Ca-1Ce涂层)耐蚀性能最佳,点蚀电位可达0.94V,比耐蚀性较好的Ca盐涂层的点蚀电位还高出0.61V,且其在浸泡11d后才出现点蚀坑。99Ca-1Ce涂层具备优良的疏水性能,且其厚度最大,与基体之间的结合力也是所有涂层中最强的,可见Ce的加入提升了Ca盐涂层的厚度、疏水性能以及涂层与基体的结合力,并进而提高了涂层的耐蚀性;但Ce含量过多会增加涂层缺陷,降低涂层与基体之间的结合力并影响其缓蚀作用的发挥,从而降低涂层的耐蚀性能。在含Ce的电解液中,由于离子迁移存在一个快慢顺序,Ce4+Ce3+Ca2+,而Ca2+一直存在于溶液中,故在涂层沉积后阶段实际发生的是Ca盐和Ce盐的共沉积。(CH_3(CH_2)_(12)COO)_2Ca涂层在Na Cl溶液的浸泡过程中可转化为(CH3(CH2)12COO)2Ca·4H2O,Ce盐涂层在浸泡过程中物相不发生转变。在长时间的浸泡下,由于涂层的溶解与脱落,基体遭受腐蚀,腐蚀产物为Mg(OH)_2。
[Abstract]:The preparation of hydrophobic coatings on magnesium alloys is a widely studied means of protection, and many studies show that the corrosion inhibition of rare earth cerium on magnesium alloys is obvious. In this experiment, a single hydrophobic coating of calcium tetradecrate, cerium tetradecanoate and cerium tetradecanoate was prepared directly on the surface of AZ31 magnesium alloy by cathodic electrodeposition, and the corrosion resistance of magnesium alloy was greatly improved by the existence of the coating. The effect of process parameters (deposition voltage and deposition time) on the morphology and corrosion behavior of single Ca salt (or ce salt) coating was studied. The effect of deposition time ratio of Ca-Ce composite coating and Ca-Ce molar ratio on morphology and corrosion behavior of Ca-Ce composite coating was also studied. It was found that the preparation process parameters of the coating significantly affected the morphology and corrosion performance of the coating. However, the phase composition of the coating does not affect the phase composition of the coating. The phase composition of the coating is that of the Ch _ 3H _ 3H _ 2o _ (12) COO _ (2) Ca _ (Ce) coating, which is composed of Ch _ (3) (Ch _ (2), Ch _ (2), (12COO) _ (4Ce) and Ch _ (3H _ (3) Ch _ (2) O _ (2) O _ (12) COO _ (3Ce). The results show that the corrosion resistance of the single Ca salt coating and ce salt coating is the best when the deposition voltage is 50 V, the longer the deposition time is, the better the corrosion resistance is for the single ce salt coating, and the better the corrosion resistance is for the single ce salt coating, the longer the deposition time is, the better the corrosion resistance is. The corrosion resistance of 60min is the best. When the deposition time ratio of Ca-Ce is 2: 1 and the molar ratio is 99:1, the hydrophobic coating (i.e. 99Ca-1Ce coating) has the best corrosion resistance. The pitting potential can reach 0.94V, which is higher than that of Ca salt coating with better corrosion resistance, and the pitting pit. 99Ca-1Ce coating has excellent hydrophobicity and its thickness is the largest. The adhesion between the coating and the substrate is also the strongest. It can be seen that the addition of ce enhances the thickness, hydrophobic property and adhesion between the coating and the substrate, and thus improves the corrosion resistance of the coating. However, excessive ce content will increase the coating defects, reduce the adhesion between the coating and the substrate, and affect the exertion of corrosion inhibition, thus reducing the corrosion resistance of the coating. In the electrolyte containing ce, there is a slow and fast sequence of ce 4 Ce3 Ca2 due to ion migration, while Ca2 exists in the solution all the time. Therefore, in the post-coating stage, the codeposition of Ca salt and ce salt is actually. Ch _ 3H _ 3H _ 2H _ 2 / C _ (12) COO _ (2H) 2Ca coating can be transformed into Ch _ 3H _ 2H _ 2CO _ 2O _ 2Ca _ 4H _ e salt coating during immersion in NaCl solution, and the phase does not change during soaking. After immersion for a long time, the substrate was corroded due to the dissolving and shedding of the coating, and the corrosion product was MgOH-2.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

【参考文献】