【作者】 王真；

【导师】 刘黎明；

【作者基本信息】 大连理工大学 ， 材料加工， 2009， 硕士

【摘要】 铝合金比强度高、耐蚀性强、可加工性好等优点使得其在航空航海等领域应用越来越广泛。铝合金在空气中具有良好的耐蚀性能,但在大量氯离子存在的环境下,如海洋环境中,容易发生点蚀。为延长大型铝合金构件的使用寿命,本课题采用经济、高效的电弧喷涂技术尝试在铝合金表面制备纯铝涂层,并将涂层封孔,进一步增强其耐蚀性。为进一步提高结构复杂涂层零件的封孔效率和封孔质量,拓展涂层封孔处理方法,首次将纯铝涂层进行沸水封孔,它对水质、操作工艺等要求较低,与阳极氧化膜的沸水封孔相比,更简便、经济。此外,为弥补有机封孔涂层绝缘性的缺陷,尝试制备环氧树脂基富铝导电耐蚀涂料,将其作为铝涂层的封孔剂。本课题主要采用常温浸泡试验及电化学试验等方法以及光学显微镜、扫描电镜、X射线衍射仪、拉曼光谱等分析手段来研究铝涂层与两种封孔涂层的耐蚀行为。运用自主研发的电弧喷涂设备,采用优化后的工艺参数:喷涂电压28V,电流100A,喷涂距离100mm,喷射角度90°,空气压力0.6MPa,成功地在6061铝合金表面制备了组织致密、结合良好的纯铝涂层,涂层起初腐蚀速率较快,但逐渐减慢,对铝合金基体可起到长期的隔离保护作用。通过系列腐蚀试验,建立了铝合金与纯铝涂层的腐蚀模型,为铝合金大型构件在海洋环境下的应用提供了理论依据。在沸水封孔过程中,去离子水与铝涂层发生反应,生成Al（OH）₃,并将大小不均的孔隙部分填补或完全堵塞。部分沸水成功地渗入到涂层内部,在涂层内部也起到了一定的封孔作用。常温浸泡试验显示,沸水封孔涂层与未封孔涂层发生了相似的腐蚀过程,但腐蚀程度明显减小。浸泡90天后,其电化学极化曲线未发生太大的变化,仍有明显的钝化区间,沸水封孔涂层比未封孔涂层有着明显优越的耐蚀性能,沸水封孔技术对电弧喷涂铝涂层是一项成功的封孔技术。在铝涂层表面尝试制备环氧树脂基富铝封孔涂层,在不影响耐蚀效果的前提下,实现封孔涂层的导电性。当铝粉含量为50wt.%时,粒子间形成导电网络,封孔涂层导电性良好。适量铝粉的加入,既没有降低环氧树脂的附着性能,也没有减弱其隔离保护作用。铝粉与环氧树脂之间以及封孔涂层与铝涂层基体之间的紧密结合、铝粉表面腐蚀产物的牢固附着与铝粉潜在的钝化使得环氧树脂基富铝封孔涂层的耐蚀性不低于环氧树脂,封孔涂层发生着缓慢而轻微的腐蚀,对电弧喷涂铝涂层起到了优异的隔离保护作用。更多还原

【Abstract】 Al alloys are more and more extensively used in various fields like aviation and marine applications for their competitive advantages including low weight,high corrosion resistance in combination with their good workability.They have perfect corrosion resistance in the air, however,will be pit corroded in marine atmosphere rich in chloride.To extend the life-span of AI alloy with large structures,the economic and efficient twin-wire arc-spray technology is employed for the deposition of pure aluminium coatings.For further corrosion resistance elevation,two new sealing methods are applied.One is the hydrothermal sealing(HTS),which is more simple and less expensive than the HTS of Al anodic film,and which can fulfill the sealing of comprehensive structures as the boiling water can reach anywhere.The other is Al-rich epoxy resin based paint,electric conductive and corrosion resistant.Here,salt solution immersion test(SSIT) and polarization curves as well as optical microscope,scanning electron microscopy(SEM) coupled with Energy-dispersive X-ray analysis system(EDX),X-Ray diffraction,electron probe microanalysis(EPMA) and Raman spectroscopy are employed for the corrosion behavior investigation of the unsealed coating and the sealed ones with the two new methods.A dense coating well joined with the substrate 6061 Al alloy is achieved using twin wire arc thermal spray system assembled by our laboratory with optimum parameters fixed:voltage 28V,arc current 100A,spraying distance 100mm,spraying angle 90°and air pressure 0.6MPa. The coating corrodes fast and gradually more and more slowly,protecting the substrate in the long run.With the analyses of series of corrosion experiments,a corrosion behavior model is established of the substrate and the coating,providing technological bases for the marine applications of A1 alloys with large structures.The HTS coating is covered with a continuous film of aluminium hydroxide structures, and some deionized water manages to penetrate.Besides,pores in the surface as well as in the inner part get smaller and fewer.In SSIT,the HTS coating has a similar corrosion process to the unsealed one,but corrodes much more slightly.After SSIT,the HTS coating exhibits small changes in polarization curves,and still displays a wide passive region,implying slight corrosion in 90 days immersion and proving much higher corrosion resistance than the unsealed coating in the whole immersion process.In a word,the HTS treatment is a successful sealing treatment for the arc sprayed Al coating.Al-rich epoxy resin based paint with acceptable surface is attempted for the first time to prepare on the arc-sprayed aluminium coating surface,corrosion resistant and electric conductive.When the Al powder reaches 50wt.%,an electrical network is formed,making the paint with good electric conductivity.Proper addition of Al particles neither degrades the adhesive properties of epoxy resin nor weakens its barrier type protection of the coating substrate.Because of the close Al particle-resin integration and the tight adhesion in the paint/coating interface,strong adherence of corrosion products on Al particles,as well as probable passivation of Al particles,the paint showed no worse corrosion resistance properties than the epoxy resin and corroded at a similar rate to the epoxy resin,slowly and slightly, protecting the coating base as a barrier type film.更多还原