铝及铝合金无铬钝化工艺及性能研究

发布时间：2018-04-30 05:41

  本文选题：铝合金 + 钝化　； 参考：《沈阳理工大学》2017年硕士论文

【摘要】：铝及铝合金是目前工业上应用较为广泛的轻金属,由于其储量大、来源广、熔点高、具有很好的延展性,因此在汽车工件、飞机机身等机械工业领域有大量需求。铝合金具有很高的塑性,可被加工成各种板材、型材、铸件应用在工业生产中。铝合金本身能够与氧气接触形成一层防止腐蚀的氧化膜,但在工业和大气环境中酸性物质、盐类物质的侵蚀程度较强,而自身氧化膜远远不能够满足防腐蚀的需要,在生产中腐蚀会造成严重的经济损失和安全隐患,因此铝及铝合金的防腐研究越来越受到人们的重视。以高效、绿色环保、简化工艺为目标,对目前存在的锆酸盐、稀土盐、钼酸盐、有机物等几类钝化体系比较优劣,筛选出氟锆酸钾钝化体系。氟锆酸钾及强氧化物组成的钝化体系具有较强的氧化性,膜层的耐腐蚀性能较好,但钝化液不稳定。因此以氟锆酸钾为主要成膜物质,研究使用添加剂来替代强氧化物,使得膜层耐蚀性能提升,并制备出稳定可重复使用的的钝化液。首先通过铝合金耐盐雾腐蚀实验和电化学极化测试的单因素试验确定氟锆酸钾的含量为2.0g/L,并优化其钝化工艺得到钝化时间7min,温度25℃,pH值3.2的钝化条件。在此基础上研究添加剂Mn(NO_3)_2和LaCl_3对膜层耐蚀性能提高的作用。确定了Mn(NO_3)_2浓度为2.4g/L时,其氧化性可使铝合金的耐蚀性能提高,达到87小时。LaCl3在0.3g/L时可促进成膜过程,使得钝化膜更加致密,耐蚀性能提高20%,达103小时。树脂作为有机物有很好的封闭作用和疏水性,能够对铝合金起到防护作用,因此本文还研究了以氟锆酸钾-树脂为主要成膜物质的无机-有机复合钝化体系。在单独氟锆酸钾最优钝化工艺的基础上,通过单因素实验确定复合体系钝化液配方,通过正交试验优化得到树脂的量为10g/L,添加偏钒酸钠1.0g/L、硅烷3ml/L,固化条件为:80℃,60min。此钝化体系及工艺可使铝合金耐盐雾腐蚀时间大大提高,达138小时,复合膜层的疏水性有所提高,附着力可达1级。并通过SEM及EDS研究了膜层的微观形貌以及膜层的元素组成分析成膜过程。
[Abstract]:Aluminum and aluminum alloys are widely used in industry at present. Because of their large reserves, wide sources, high melting point and good ductility, aluminum and aluminum alloys have a large demand in the field of mechanical industry such as automobile parts, aircraft fuselage and so on. Aluminum alloy has high plasticity, can be processed into various plates, profiles, castings used in industrial production. Aluminum alloy itself can contact with oxygen to form a corrosion resistant oxide film, but in the industrial and atmospheric environment, the corrosion degree of acid substances, salt substances is relatively strong, and its own oxide film is far from meeting the need of corrosion prevention. Corrosion in production will cause serious economic losses and safety risks, so people pay more and more attention to the corrosion protection of aluminum and aluminum alloys. Aiming at high efficiency, green environmental protection and simplified technology, the passivation system of potassium zirconate, potassium zirconate, molybdate, organic compound and so on was selected. The passivation system was compared with that of zirconate, rare earth salt, molybdate and organic matter. The passivation system composed of potassium fluoride zirconate and strong oxides has strong oxidation property and good corrosion resistance, but the passivation solution is unstable. Therefore, using potassium zirconate as the main film-forming material, the additive was used to replace the strong oxide to improve the corrosion resistance of the film, and a stable and reusable passivation solution was prepared. Firstly, the content of potassium zirconate was determined to be 2.0 g / L by single factor test of salt spray corrosion resistance and electrochemical polarization test of aluminum alloy, and the passivation conditions of passivation time of 7 min and pH value of 3.2 at 25 鈩，

本文编号：1823343