一浴法热浸镀铝的后处理及钝化工艺
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摘要
一浴法热浸镀铝时,在镀铝层表面附着一层由KCl-NaCl-NaF-AlF3组成的熔剂和一些污物,使镀铝产品的外表面极不美观,而且对铝镀层有腐蚀作用,还会干扰后面的钝化处理。因此,该熔剂和污物必须要除去,之后再对镀件进行钝化处理。在钝化过程中,广泛使用的铬酸盐,因其毒性高、危害人体健康且污染环境,因此研究新的热浸镀铝层的无铬钝化技术来取代铬酸盐钝化势在必行。
本文系统地研究了热浸镀铝的后处理及钼酸盐钝化工艺,制备出了更加有效的后处理液及钼酸盐钝化液。比较了经新配方后处理与传统后处理所得铝镀层的宏观形貌和它们的防腐性能。并探讨了它们的成膜机制和耐蚀机理；用盐雾腐蚀试验(NSS)、盐水浸泡试验和电化学等测试手段,对钝化膜的耐蚀性能进行了比较。
通过正交试验确定了后处理剂配方的最佳范围：HN03浓度为5%-10%；HF浓度为0.25%-1.5%；表面活性剂A为0.10-0.15g·L-1；表面活性剂B为0.05-0.15g·L-1；处理时间为120-200s。以及钼酸盐钝化剂的最佳范围：pH值为2-3.5, Na2MoO4·2H2O的浓度和NaH2PO4的浓度均为15-20g/L,钝化液处理温度为30-60℃,处理时间为40-60s,适量添加剂。
与传统后处理液相比,采用的新后处理液处理的试样,通过面扫描结果可知,试样表面覆盖盐减少了2/3以上。经恒定湿热试验、交变湿热试验结果表明：新配方后处理试样覆盖盐脱除能力优于传统配方。
通过盐雾试验、盐水浸泡试验和电化学试验可知,钼酸盐钝化后试样的耐蚀性明显优于未钝化的试样。理论上,钝化膜在铝层表面起到了物理屏障作用,能抑制腐蚀过程的发生,推迟铝层产生锈的时间,从而显著提高了热浸渡铝层的耐蚀性。
In the procrss of hot dip aluminizing with the one flux bath method, there are dirts and fluxes composed of KCl-NaCl-NaF-AlF3 on the surface of aluminum coating, which make the appearance of the aluminum production undecorated, and have some corrsion for the aluminum coating. So that,. These dirts and fluxes must be cleared, and do some passivation on the aluminum coating. In the process of passivation, the toxic wildly used chromate not only endangers humans, but pollutes the enviorment. So the research on the hot dip aluminuming without chromium in the passvation is imperative.
The study systematically has incestigated the post-procesing of hot dip aluminum and tha passvation without chromium, and prepared more available post-processing liquid and passvation liquid without chromium, compared the surface morphology of samples with new or traditional post-processing, and their effectiveness of corrsion resistance. With observing and analyzing the component and structure of the molydate passivation film, and discusse the mechanism of filming and anticorrsion; even compare the corrsion resistance of passivating film by the salt spray test, saline immersing test and electrochemical test.
According orthogonal test the optimum range of the post-treatment agent formula is determined:The concentration of HNO3 and HF is 5%-10%, and 0.25%-1.5%.and the concentration of surfactant A and B is 0.10-0.15g·L-1 and 0.05-0.15g·L-1, the passivae time is 60s, with optimum addition.
Compared to tradtional post-processing liquid, the salt on the surface of sample being new post-processed has reduced at lest 2/3, according the result of surface scan. The result of the fixed and alternative damp heat test shows:the salt removing of the sample with new post-processing is better than the traditional one.
The corrsion resistance of the sample with molybdate passivation is better than the one without passivation, according the salt spray test, saline immersing test and electrochemical test. In theory, the passive film resists the corrsion and delays the rusting as a physical barrier on the surface of aluminum coating, that evidently enhance the resistance corrsion.
本文系统地研究了热浸镀铝的后处理及钼酸盐钝化工艺,制备出了更加有效的后处理液及钼酸盐钝化液。比较了经新配方后处理与传统后处理所得铝镀层的宏观形貌和它们的防腐性能。并探讨了它们的成膜机制和耐蚀机理；用盐雾腐蚀试验(NSS)、盐水浸泡试验和电化学等测试手段,对钝化膜的耐蚀性能进行了比较。
通过正交试验确定了后处理剂配方的最佳范围：HN03浓度为5%-10%；HF浓度为0.25%-1.5%；表面活性剂A为0.10-0.15g·L-1；表面活性剂B为0.05-0.15g·L-1；处理时间为120-200s。以及钼酸盐钝化剂的最佳范围：pH值为2-3.5, Na2MoO4·2H2O的浓度和NaH2PO4的浓度均为15-20g/L,钝化液处理温度为30-60℃,处理时间为40-60s,适量添加剂。
与传统后处理液相比,采用的新后处理液处理的试样,通过面扫描结果可知,试样表面覆盖盐减少了2/3以上。经恒定湿热试验、交变湿热试验结果表明：新配方后处理试样覆盖盐脱除能力优于传统配方。
通过盐雾试验、盐水浸泡试验和电化学试验可知,钼酸盐钝化后试样的耐蚀性明显优于未钝化的试样。理论上,钝化膜在铝层表面起到了物理屏障作用,能抑制腐蚀过程的发生,推迟铝层产生锈的时间,从而显著提高了热浸渡铝层的耐蚀性。
In the procrss of hot dip aluminizing with the one flux bath method, there are dirts and fluxes composed of KCl-NaCl-NaF-AlF3 on the surface of aluminum coating, which make the appearance of the aluminum production undecorated, and have some corrsion for the aluminum coating. So that,. These dirts and fluxes must be cleared, and do some passivation on the aluminum coating. In the process of passivation, the toxic wildly used chromate not only endangers humans, but pollutes the enviorment. So the research on the hot dip aluminuming without chromium in the passvation is imperative.
The study systematically has incestigated the post-procesing of hot dip aluminum and tha passvation without chromium, and prepared more available post-processing liquid and passvation liquid without chromium, compared the surface morphology of samples with new or traditional post-processing, and their effectiveness of corrsion resistance. With observing and analyzing the component and structure of the molydate passivation film, and discusse the mechanism of filming and anticorrsion; even compare the corrsion resistance of passivating film by the salt spray test, saline immersing test and electrochemical test.
According orthogonal test the optimum range of the post-treatment agent formula is determined:The concentration of HNO3 and HF is 5%-10%, and 0.25%-1.5%.and the concentration of surfactant A and B is 0.10-0.15g·L-1 and 0.05-0.15g·L-1, the passivae time is 60s, with optimum addition.
Compared to tradtional post-processing liquid, the salt on the surface of sample being new post-processed has reduced at lest 2/3, according the result of surface scan. The result of the fixed and alternative damp heat test shows:the salt removing of the sample with new post-processing is better than the traditional one.
The corrsion resistance of the sample with molybdate passivation is better than the one without passivation, according the salt spray test, saline immersing test and electrochemical test. In theory, the passive film resists the corrsion and delays the rusting as a physical barrier on the surface of aluminum coating, that evidently enhance the resistance corrsion.
引文
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2.范晓明,李凌,刘生发等.钢铁零件热浸镀铝工艺的研究及发展概况[J],铸造工程·造型材料,2003,2：19-20.
3.李国喜.钢材热浸镀工艺的研究与应用[J],材料保护,1993,23(9)：11-12.
4.张翠兰.我国熔剂法热浸镀铝工艺发展概况[J],金属热处理,1995,13(1)：3-5.
5.陈军.工艺变化对热浸镀铝影响的研究[J],热加工工艺,1999,43(2)：38-40.
6.刘邦津.钢材的热浸镀铝[M],北京：冶金工业出版社,1995,1-8,94-96.
7.陈东,金向雷.国内外热浸镀铝技术进展述评[J],河北冶金,1997,17(3)：25-30.
8.顾国成.表面处理钢材的生产与应用[M],北京：科学技术文献出版社,1989,67-68.
9.王德庆,于金龙,段旭东.钢铁表面热浸镀铝技术回顾[J],大连铁道学院学报,2003,24(3)：77-83.
10.郑毅然,高文禄.热浸镀铝钢材料的应用与进展[J],腐蚀科学与防护技术,1996,9(1)：179-183.
11.俞敦义,罗吉媛,杨继林等.渗铝钢在硫化氢盐水体系中的腐蚀研究[J],华中理工大学学报,2000,28(11)：113-116.
12.罗吉媛,俞敦义,杨继林.渗铝钢在Na2S溶液中的腐蚀行为研究[J],材料开发与应用,2000,15(4)：14-25.
13.李华飞,余敦义.热浸镀铝钢的性能及用途[J],材料保护,2001,34(5)：21-23.
14. I. E. Nicholls. Hot-dipped aluminum coatings[J], Corrosion Technology,1964,35(10): 16-21.
15. Li Ya-jiang. Characteristics of phase constitution in the Fe-Al alloy layer of calorized steel pipe[J], Materials Science,1995,30(6):2635-2639.
16. L. Gerhard. The influence nitrogen content of dip aluminized steel sheet on the growth of the Fe2Al5 intermetallic com-pound layer[J], Practical Metallography,1977,14(8): 251-259.
17.夏原,姚枚,李铁藩.Q235钢热浸铝初期镀层组织结构的变化[J],金属热处理学报,1998,19(2)：34-38.
18. T. Heumann, N. Dittrich. Structure character of the Fe2Al5 in-termetallics compound in hot dip aluminizing process[J], Z Metallk,1959,50(6):617-624.
19.林建强,刘海龙,宋诚忠等.钢热浸镀铝的镀层组织分析[J],热加工工艺,1999,15(3)：20-21.
20.曲敬信,汪泓宏.表面工程手册[M],北京：化学工业出版社,1998,637-642.
21.李金桂,吴再思.防腐蚀表面工程技术[M],北京：化学工业出版社,2002,209-211,217-21,228-231.
22. Wilcox, D. R. Gabe, M. E. Warwick. The development of passivation coatings by cathodic reduction in sodium molybdate solutions [J], Corrosion Science,1988,28(6): 577-579.
23.佐藤教男,蒋忠锦.金属的钝化和表面钝化膜[J],表面技术,1980,26(01)：45-47.
24.安茂忠.电镀理论与技术[M],哈尔滨工业大学出版社,2004,9-10.
25.李家柱,林安,甘复兴.取代重污染六价铬电镀的技术及应用[J],电镀与涂饰,2004,18(05)：32-34.
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