摘要
镁合金是实际应用中最轻的金属结构材料,具有高的比强度、比刚度和减振性,而且易于回收,在汽车、电子、航空等领域得到广泛的应用。但是,镁合金的耐蚀性比较低,使它的应用受到很大的限制。本文着重研究了影响Mg-Al-Zn系合金耐蚀性的内在因素和提高该系合金的耐腐蚀性措施。
采用金相显微镜、扫描电镜、失重法、集气法和极化曲线,研究了主要合金元素铝锌锰、相、铸造缺陷和铸造状态对Mg-Al-Zn合金腐蚀性能的影响。结果表明:铝含量增加,耐蚀性降低;适量的锌可以提高耐蚀性;一定范围内,随着锰含量的增加,耐蚀性增加;第二相的电位比镁基体的电位高,加速了合金的腐蚀;铸造缺陷容易造成局部腐蚀,降低了合金的耐蚀性;快速冷却的合金由于表面组织致密和缺陷少,耐蚀性较高。
采用化学转化、阳极氧化、化学镀镍等表面处理方法,在Mg-Al-Zn系合金上得到保护膜。通过观察表面膜形貌、测量表面膜成分和腐蚀试验研究了表面膜的特性。结果表明:一步处理化学转化法操作简单,使用温度低,槽液稳定,得到的转化膜与基体结合良好,耐蚀性比较好;阳极氧化得到的膜比化学转化得到的膜平整,孔隙率低,与基体的结合力高,耐蚀性好;这两种保护膜大部分不能直接用作防护表面,而是用作其他有机涂层的底层;在不冲洗化学镀镍在进行碱性化学镀镍之前形成一层水膜,这层水膜能够使镀液在试样表面形成良好的镀层,镀层与基体结合良好,性能优越,耐蚀性高。
本文新见解:Mg-Al-Zn系合金的抗腐蚀性比较差;一步处理化学转化得到的保护膜性能优良;阳极氧化得到的保护膜孔隙少,耐蚀性高;不冲洗化学镀镍在碱性化学镀镍之前形成的那层水膜使化学镀镍变得容易,使镀层的质量提高。
As the lightest metal structural material, magnesium alloys are found using widely in automotive, electronic and aeronautical industries because of a number of desirable features, including high strength/weight, high hardness/weight, damping characteristic and recycled easily. However, their applications are limited severely for their low corrosion resistance. The corrosion properties of Mg-Al-Zn alloys and the measures to improve their corrosion resistance are researched in this paper.
The influences of main elements, phases, defects and casting-state to corrosion resistance of Mg-Al-Zn alloys are researched by optical microscope, scan electron microscope, weight-loss test, collecting gas test and polarization curves in this paper. The results show that corrosion resistance reduces with increasing aluminum and improves by adding some zinc and enhances to some extent with increasing manganese. All the secondary phases speed corrosion for their high potentials, defects reduce corrosion resistance because they make localized corrosion happen easily. The corrosion resistance of rapid-cooling alloys is high for their compact structure and little defects.
The protective films on Mg-Al-Zn alloys forms by chemical conversion, anodic oxidation and electroless nickel plating. The properties of the films are researched through observing morphology of films, analyzing compositions of films and corrosive experiments . The results show that one-step treatment chemical conversion has many excellences such as simple operation, low treatment temperature and steady-going solution. The chemical conversion film connects well with matrix and has high corrosion resistance. Anodic oxidation film connects well with matrix and has high corrosion resistance for its much less holes and smooth surface. Most of the two protective flims are used directly as protective surface while used as the bottom of other organic coating. During unwash electroless nickel plating, the water film that forms before the alkaline electroless nickel plating makes plating-coating connect well with matrix. The coating has excellent properties and high corrosion resistance.
The new opinions in this paper are that the corrosion resistance of Mg-Al-Zn alloys is very poor. The protective ability of the film formed in one-step treatment chemical conversion is very good. Anodic oxidation film has low holes ratio and high corrosion resistance. The water film that forms before the alkaline electroless nickel plating makes electroless nickel plating easier and improves the quality of the coating .
引文
1.波尔米尔著,陈昌麒,邹愉译.轻合金.北京,国防工业出版社,1994
2.轻金属材料加工手册编写组.轻金属加工手册(上册).北京,冶金工业出版社,1979
3.朱祖芳等.有色金属的耐腐蚀性及其应用.北京-化学工业出版社,1995.6
4.陶令恒等.铸造手册(非铁合金卷).机械工业出版社,1994
5.杨遇春.有色金属在汽车工业中的应用前景[J].材料导报,1993,6(6):19~22
6.卡恩R W,哈森P,克雷默E J,丁道云等译.材料科学与技术丛书,第8卷,非铁合金的结构与性能[M].北京:科学出版社,1999.101~182
7. Raymond F,Decker. The Renaissance in magnesium[J]. Adv Mate Pro, 9/1998, 154(3):31-33
8. Enley E F. Principles of Magnesium Technology[M].Headington Hill Hall, Oxford Pergamon Press Ltd, 1966
9. Barton TF, Johnson CB. The effect of electrolyte on the anodized finish of magnesium alloy [J]. Plating and Surface Finishing, 1995,82(5): 138~141
10. Froes F H, Eliezer D. The Science, Technology and Application of Magnesium[J]. J Mine Metals and Mater Soc. 1998,5(9):30~34
11. Allan Forats, Terje Kr. Aune, David Hawkeetal. Metal Handbook 9th Edition (Vol 12) Corrosion [M]. USA:ASM International, 1987. 740-754
12. Enley E F. Principles of Magnesium Technology[M]. Headington Hill Hall, Oxford: Pergamon Press Ltd, 1966
13.任学佑.有色金属在轿车工业中的应用前景[J].有色金属.1998,50(3):114~119
14.佟丽红.汽车制造业使用镁的现状与潜力.有色金属.2002年第8期
15.王滨.用镁合金铸造的便携式个人计算机外壳[J].轻金属加工技术,1996,24:43.6
16.钟皓,刘培英,周铁淘.镁及镁合金在航空航天中的应用及前景.航空工程与维修,2000.4
17.陈亚莉.航空用铸镁合金的发展.中国航空信息中心.1998年第5期
18.黄少东,唐泉波,赵祖德,刘川林,曹洋,赵军.用镁合金促进兵器装备轻量化.金属成型工艺.Vol.20,No.5,2002
19.刘正,张奎,曾小勤著.镁基轻质合金理论基础及其应用.机械工业出版社,2002.9
20. BARIL G, PEBERE N. The corrosion of pure Magnesium in aerated and sodium sulphate solution [J]. Corrosion Science, 2001,43:471-484
21. Makar G L,Kruger J. Corrosion of Magneium[J].International Materials Reviews. 1993,38(3):138~153
22. Gangling Song, Aanrej Atrens, Matthew Dargusch. Influence of Microstructure on the Corrosion of Die-cast AZ91D[J].Corrosion Science. 1999,41(2):249~273
23. Nakatsugawa I, Martin R, Knystautas E J. Improving Corrosion Resistanceof AZ91D Magnesium Alloy by Nitrogen Ion Implantation[J].Corrosion. 1996,52(12):921~926
24. Rudd A L, Breslin C B, Mansfeld F. The Corrosion Protection Afforded by Rare Earth Conversion Coatings Applied to Magnesium [J].Corrosion Science. 2000,42(2):275~288
25.中国腐蚀与防护学会主编.化学转化膜[M].北京:化学工业出版社,1988
26.张洪生.无毒植酸在金属防护中的应用[J].电镀与精饰.1999,18(4):38~41
27.陈洪希.肌醇六磷酸酯在低温磷化液中的应用[J].四川化工与腐蚀控制.2000,3(4)
28.曾爱平,薛颖,钱宇峰等.镁合金表面改性新技术[J].材料导报.2000,14(3):19 20
29.曾华梁,杨家昌编译.电解和化学转化膜.轻工业出版社.1987.4
30.高云震.任继嘉,宁福元编译.表面处理.冶金工业出版社.1991.8
31. Alex J Z, Duane E B. Anodized Coatings for Magnesium Alloys[J].Metal Finishing. 1994,92(3):39~44
32.姜晓霞,沈伟著.化学镀理论及实践.国防工业出版社.2000.6
33. Guang Ling Song, Andrej Atrens. Corrosion mechanisms of magnesium alloys. ADERVANCED ENGINEERING MATERIALS
34. H.B. Yao, Y. Li,A.T.S. Wee. An XPS investigation of the oxidation and corrosion of melt-spun Mg. Applied Surface Science 158.2000
35. Z. Lu, A. Schechter, M. Moshkovich, D. Aurbach. On the electrochemical behavior of magnesium electrodes in polar aprotic electrolyte solution. Journal of Electroanalytical Chemistry 466(1999)203-217
36. G. SONG, A. ATRENS, D. STJOHN, J. NAIRN and Y. LIT. THE ELECTROCHEMICAL CORROSION OF PURE MAGNESIUM IN I N NaCI. Corrosion Science. Vol. 39, No. 5,855-875,1997
37.林高用,彭大署,张辉等.AZ91D镁合金锭耐腐蚀性能研究.矿业工程.Vol.21,No.3,2001
38. Genevi_eve Baril, Nadine P_eb_ere. The corrosion of pure magnesium in aerated and deaerated sodium sulphate solutions Corrosion Science 43 (2001) 471±484
39. S. Mathieu, C. Rapin, J. Steinmetz, P. Steinmetz. A corrosion study of the main constituent phases of AZ91 magnesium alloys Corrosion Science 45 (2003) 2741-2755
40. M. Vilarigues, L.C. Alves, I.D. Nogueira, N. Franco, A.D. Sequeira, R.C. da Silva. Characterisation of corrosion products in Cr implanted Mg surfaces. Surface and Coatings Technology 158-159 (2002) 328-333
41. J. I. Skar. Corrosion and corrosion prevention of magnesium alloys. Materials and Corrosion 50, 2±6 (1999)
42. M. Andrei, F. di Gabriele, P.L. Bonora and D. Scantlebury. Corrosion behaviour of magnesium sacrificial anodes in tap water. Materials and Corrosion 54,5-11(2003)
43.李金桂,赵闺彦等.腐蚀与腐蚀控制手册.北京,国防工业出版社.1988.7
44. Guangling Song, David StJohn. Corrosion behaviour of magnesium in ethylene glycol.
Corrosion Science (2003)
45. R. Lindstrom, L.G. Johansson, J.E. Svensson. The influence of NaCl and CO_2, on the atmospheric corrosion of magnesium alloy AZ91. Materials and Corrosion 54, 587-594 (2003)
46. H. Inoue, K. Sugahara, A. Yamamoto, H. Tsubakino. Corrosion rate of magnesium and its alloys in buffered chloride solutions. Corrosion Science 44(2002)603-610
47. Rakel Lindstrom, Lars-Gunnar Johansson, George E. Thompson, Peter Skeldon, Jan-Erik Svensson. Corrosion of magnesium in humid air. Corrosion Science (2004)
48. GUANGLING SONG, ANDREJ ATRENS, XIANLIANG WU, BO ZHANG. CORROSION BEHAVIOUR OF AZ21, AZ501 AND AZ91 IN SODIUM CHLORIDE. Corrosion Science, Vol. 40, No. 39, pp. 1769-1791,1998
49.林秋华.可溶性盐对镁与水反应的影响.中学化学教学参考.2000年第4期
50.卢燕平,屈祖玉.化学转化膜的改性与耐蚀性研究.材料保护.Vol.36,No.4,Apr.2003
51. Kwo Zong Chong, Teng Shih Shih. Conversion-coating treatment for magnesium alloy by a permanganate-phosphate solution. Materials Chemistry and Physics 80 (2003) 191-200
52. Hongwei Huo, Ying Li, Fuhui Wang. Corrosion of AZ91D magnesium alloy with a chemical conversion coating and electroless nickel layer. Corrosion Science (2003)
53. Manuele Dabala, Katya Brunelli, Enrico Napolitani, Maurizio Magrini. Cerium-based chemical conversion coating on AZ63 magnesium alloy. Surface and Coatings Technology 172(2003)227-232
54. Y.Mizutani, S.J. Kim, R. Ichino, M. Okido. Anodizing of Mg alloys in alkaline solutions. Surface and Coatings Technology 169-170(2003) 143-146
55. F.A. Bonilla, A. Berkani, P. Skeldon, G.E. Thompson, H. Habazaki, K. Shimizu , C. John, K. Stevens. Enrichment of alloying elements in anodized magnesium alloys. Corrosion Science 44 (2002) 1941-1948
56. X.W. Guo, W.J. Ding, C. Lu, C.Q. Zhai. Influence of ultrasonic power on the structure and composition of anodizing coating formed on Mg alloys. Surface and Coatings Technology (2003)
57. V. Fournier, P. Marcus. and I. Olefjord. Oxidation of magnesium. Surf. Interface Anal. 2002, 34:494-497
58. H. Umehara, M. Takaya, S. Terauchi. Chrome-free surface treatments for magnesium alloy. Surface and Coatings Technology 169-170(2003)666-669
59. Yongjun Zhang, Chuanwei Yan, Fuhui Wang, Hanyi Lou, Chunan Cao. Study on the environmentally friendly anodizing of AZ91D magnesium Alloy. Surface and
Coatings Technology 161(2002)36-43
60. Oscar Khaselev, Danny Weiss, Joseph Yahalom. Structure and composition of anodic films formed on binary Mg-Al alloys in KOH-aluminate solutions under continuous sparking. Corrosion Science 43 (2001) 1295-1307
61. Y. Mizutani, S.J. Kim, R. Ichino, M. Okido. Anodizing of Mg alloys in alkaline solutions. Surface and Coatings Technology 169-170(2003) 143-146
62.叶宏,冯燕熹,王希山.镁合金化学镀镍工艺研究.SURFACE TECHNOLOGY.Vol.31,NO.6,Dec.2002
63.戴长松,吴宜勇,王殿龙,胡信国.镁及镁合金的化学镀镍.兵器材料科学与工程.第20卷,第4期.1997年7月
64.向阳辉,刘新宽,胡文彬,赵昌正,丁文江.镁合金化学镀镍的磷含量控制.电镀与保护.第21卷第2期,2001.3
65.向阳辉,胡文彬,沈彬,赵昌正,丁文江.镁合金直接化学镀镍活化表面状态对镀速的影响.电镀与环保.2000年3月
66.向阳辉,胡文彬,沈彬,赵昌正,丁文江.镁合金直接化学镀镍的初始沉积机制.上海交通大学学报.第34卷第12期,2000年12月
67.霍宏伟,李瑛,王福会.AZ91D镁合金化学镀镍.中国腐蚀与防护学报.第22卷第1期,2002年2月
68.薛方勤,韩夏云,郭忠诚.镁及镁合金表面化学镀Ni-P合金新工艺.材料保护.第35卷第9期,2002年9月
69. Rajan Ambat, W. ZHOU. Electroless nickel-plating on AZ91D magnesium alloy: effect of substrate microstructure and plating parameters. Surface and Coatings Technology (2003)
70. A.K. Sharma, M.R. Suresh, H. Bhojraj, R.P. Sahu. Electroless Nickel Plating onMagnesium Alloy