自润滑型无铬钝化涂层成膜机制及润滑性能研究

发布时间：2018-04-05 02:05

  本文选题：自润滑膜层　切入点：热镀锌钢板　出处：《昆明理工大学》2016年博士论文

【摘要】：传统的镀锌板表面钝化工艺主要采用六价铬钝化处理。但是,六价铬是剧毒物质,对人体和环境都有严重危害,含有六价铬的产品受到了严格的限制。此外,随着镀锌板加工工艺对膜层的要求逐渐提高,对耐热性、耐水性、自润滑性以及耐腐蚀性等要求越来越苛刻。因此,开发无铬自润滑型钝化工艺技术,解决六价铬的污染问题,是绿色工业技术的大势所趋。1)通过响应面曲线法筛选出最佳无铬自润滑型钝化液配方：复合硅烷偶联剂3.88%,钼酸铵1.55%,纳米硅溶胶3.53%,单宁酸3.15%,水性苯丙乳液3.4%和水性聚乙烯蜡0.15%。最终,自润滑液的固体份为15%-16%、粘度为6.5-7 mPa·S、密度为1.01～1.02kg/dm3、pH值为6.5；2)使用加压辊涂的先进工艺制备了均匀、透明的无铬自润滑膜,并建立自润滑皮膜量工业化生产标准曲线；利用扫描电镜、X射线光电子能谱、辉光放电发射光谱和红外光谱等手段对膜层微观特征进行分析；通过电化学测试及盐雾试验对膜层耐蚀性进行了对比研究,分析了耐指纹性、耐水性和耐热性等表面性能,实验表明自润滑膜层性能优异；3)研究了无铬自润滑膜层的成膜机制：(i)硅烷分子在镀锌板表面形成致密的空间立体网状结构,将无机缓蚀剂包覆在膜的内部；(ii)锌和钼酸铵反应生成的钼酸锌填充在网状硅烷膜内；(iii)水性苯丙乳液和聚乙烯蜡在硅烷膜上形成均匀稳定的自润滑膜层;分析了无铬自润滑型钝化膜层的耐蚀机理：首先水性苯丙乳液形成的均匀膜层,阻挡腐蚀性介质向金属基体的扩散：其次钼酸铵反应形成化合物和单宁酸形成的化合物同时提高自润滑膜层的电阻,抑制腐蚀反应,降低反应速度,从而达到缓蚀目的；4)对无铬自润滑型钝化镀锌板冲压过程进行了数值建模和有限元模拟,表明钝化镀锌板加工生产时,应该尽量考虑使用轧制方法,避免使用大载荷的冲压/挤压方式：得出自润滑型钝化膜最佳使用参数为：填充剂配比为0.48,膜层厚度为900mg/m2,温度150℃,载荷150 N；且具有自润滑性的钝化镀锌板冲压性能明显优于其他产品。无铬自润滑型钝化膜目前已经在工业上得到了实际的应用和推广,本研究获得国家科技部863计划资助,取得的研究成果对自润滑钝化膜的研究和发展具有非常重要的参考价值。
[Abstract]:The traditional galvanized plate surface passivation process mainly adopts hexavalent chromium passivation treatment.However, hexavalent chromium is a highly toxic substance, which is seriously harmful to human body and environment, and the products containing hexavalent chromium are strictly restricted.In addition, with the process of zinc plating, the requirements of coating are gradually improved, and the requirements of heat resistance, water resistance, self-lubricity and corrosion resistance are becoming more and more stringent.Therefore, the development of chromium-free self-lubricating passivation technology to solve the pollution problem of hexavalent chromium,It is the general trend of green industrial technology. 1) the best formula of chromium-free self-lubricating passivation solution is selected by response surface curve method: compound silane coupling agent 3.88, ammonium molybdate 1.55um, nano-silica sol 3.53, tannic acid 3.15g, waterborne styrene-acrylic emulsion 3.4% and waterborne polyethylene wax 0.15.Finally, the solid content of self-lubricating liquid is 15-16, the viscosity is 6.5-7 mPa / s, the density is 1.01 ~ 1.02kg / dm ~ (3) and pH value is 6.5 ~ (2)) the uniform and transparent chromium-free self-lubricating film is prepared by using the advanced technology of pressure roller coating, and the standard curve of industrialized production of self-lubricating film is established.The microcosmic characteristics of the film were analyzed by means of X-ray photoelectron spectroscopy, glow discharge emission spectrum and infrared spectrum, the corrosion resistance of the film was studied by electrochemical test and salt spray test, and the fingerprint resistance was analyzed.Surface properties such as water resistance and heat resistance. The experimental results show that the self-lubricating film has excellent performance. (3) the film forming mechanism of chromium-free self-lubricating film is studied. The silane molecule forms a dense three-dimensional reticular structure on the surface of galvanized sheet.Zinc molybdate, which was formed by the reaction of zinc with ammonium molybdate, was filled in the reticulated silane film with aqueous styrene-acrylic emulsion and polyethylene wax to form a uniform and stable self-lubricating film layer on the silane film.The corrosion resistance mechanism of chromium-free self-lubricating passivation film was analyzed.Secondly, ammonium molybdate reacts to form compound and tannic acid to form compound. Meanwhile, the resistance of self-lubricating film is increased, corrosion reaction is inhibited and reaction speed is reduced.The stamping process of chromium-free self-lubricated passivated galvanized sheet is modeled and simulated by finite element method. It is shown that rolling method should be taken into account when passivation galvanized sheet is produced.Avoid the use of heavy load stamping / extrusion: the best parameters of self-lubricating passivation film are: filling ratio 0.48, thickness of film 900mg / m2, temperature 150 鈩，

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