稀土镁合金微弧氧化深色陶瓷膜的制备
摘要
本文采用微弧氧化技术在SJDM-1稀土镁合金表面获得了不同色度的耐腐蚀性好的陶瓷膜层,膜层显示不同的颜色是由于膜层中着色剂的种类及配比引起的。经过SEM、XRD、膜层测厚仪和点滴实验、盐雾实验等测试,分析结果表明此陶瓷层相组成主要为MgO、ZnO、Zr_3O、Mg_2SiO_4和Mg_(14)(SiO_4)_5O_4和着色剂的氧化物,而且膜层致密度越高,耐蚀性越好,膜层经过盐雾实验96小时,腐蚀级别为10级,微弧氧化后水合封孔的稀土镁合金耐蚀性是未封口的19倍,并且阴极材质、距离、面积对陶瓷层耐蚀性都有影响。
陶瓷层腐蚀的主要原因是膜层表面发生的大阴极小阳极的点腐蚀过程。电解液失效是因为微弧氧化过程中电解质之间、电解质和水及其它介质(如空气)之间发生了复杂的化学反应。
In this dissertation, the different color ceramic coatings of the good corrosion resistance were obtained by micro-arc oxidation technology on the SJDM-1 Rare earth magnesium-alloys surface. The ceramic coatings showed different color is due to the type and the proportion of the coloring agents in the film. After SEM, XRD, the coating thickness tester and drop experiment, the salt spray corrosion experiment, the analysis was shown that this ceramic layer was mainly composed of MgO, ZnO, Zr_3O, Mg_2SiO_4 and Mg_(14)(SiO_4)_5O_4 and the oxides of coloring agents, and the higher the density of the film, the better corrosion resistance of the film. In addition, after 96 hours of salt spray corrosion experiment, the rating of corrosion was 10. The corrosion resistan of the rare earth magnesium-alloys after sealing hydrated was not sealed 19 times after micro-arc oxidation, and the cathode material, distance, area on the corrosion resistance of ceramic layer had implications.
The main reason of ceramic layer corrosion was point corrosion process of the big cathode small anode that happend on the surface of coatings. Failure electrolyte was because there were complex chemical reactions between the electrolyte and electrolyte, the electrolyte and water and other media (such as air) in the micro-arc oxidation process.
陶瓷层腐蚀的主要原因是膜层表面发生的大阴极小阳极的点腐蚀过程。电解液失效是因为微弧氧化过程中电解质之间、电解质和水及其它介质(如空气)之间发生了复杂的化学反应。
In this dissertation, the different color ceramic coatings of the good corrosion resistance were obtained by micro-arc oxidation technology on the SJDM-1 Rare earth magnesium-alloys surface. The ceramic coatings showed different color is due to the type and the proportion of the coloring agents in the film. After SEM, XRD, the coating thickness tester and drop experiment, the salt spray corrosion experiment, the analysis was shown that this ceramic layer was mainly composed of MgO, ZnO, Zr_3O, Mg_2SiO_4 and Mg_(14)(SiO_4)_5O_4 and the oxides of coloring agents, and the higher the density of the film, the better corrosion resistance of the film. In addition, after 96 hours of salt spray corrosion experiment, the rating of corrosion was 10. The corrosion resistan of the rare earth magnesium-alloys after sealing hydrated was not sealed 19 times after micro-arc oxidation, and the cathode material, distance, area on the corrosion resistance of ceramic layer had implications.
The main reason of ceramic layer corrosion was point corrosion process of the big cathode small anode that happend on the surface of coatings. Failure electrolyte was because there were complex chemical reactions between the electrolyte and electrolyte, the electrolyte and water and other media (such as air) in the micro-arc oxidation process.
引文
1范才河,陈刚,严红草,等.稀土在镁合金中的作用.材料导报.2005,219(7):61～62
2李卫平,朱立群.镁及其合金表面防护性涂层国外研究进展.材料保护.2005,38(2):41～45
3祁庆琚,刘永兵,杨晓红.镁合金的研究及其在汽车工业中的应用与展望.汽车工程.2002,24(2):94～100
4李德辉,董杰,曾小勤,等.高性能稀土镁合金研究进展.材料导报.2005,19(8):51～53
5郭旭涛,李培杰,刘树勋,等.稀土耐热镁合金发展现状及展望.铸造.2002,51(2):68～68
6郭旭涛,李培杰,曾大本.稀土在耐热镁合金中的应用.稀土.2002,23(2):63～63
7陈振华.镁合金.北京:化学工业出版社,2004:219～223
8 Anselm Kuhn. Plasma Anodizing of Magnesium Alloys. Metal Finishing. 2003, (9):44～50
9陈振华.变形镁合金.北京:化学工业出版社,2005:326～329
10张永君.镁及镁合金环保型阳极氧化表面改性技术研究:[博士学位论文].沈阳:中国科学院金属研究所,2003
11 J.E. Gray, B. Luan. Protective Coatings on Magnesium and Its Alloys-A Critical Review. Journal of Alloys and Compounds. 2002, 336: 88～113
12 Sundararajan G, Ramakrishna L. Mechanisms underlying the formation of thick aluminum coatings through the MAO coating technology. .Surface and Technology. 2003, 167: 269～277
13 Schreckenbach J, Schlottig F, Marx G, et al. Preparation and microstructure characterization of anodic spark deposited barium titanate films. J Mater Res. 1993, 13: 1437～1443
14 Gnedenkov S. V, Gordienko P. S, Sinnebryukhov S. L, et al. Antiscuff coatings obtained by micro-arc oxidation of titanium alloys. Russian Journal of Applied Chemistry. 2000, 73: 6～9
15边风刚,李国禄,刘金海,等.镁合金表面处理的发展现状.材料保护.2002,35(3):2～2
16 Yerokhin A L, Nie X, Leyland A, et al. Plasma electrolysis for surface engineering. Surface and Coating Technology. 1999, 122: 73～79
17许越,陈湘,吕祖舜,等.AZ91镁合金表面稀土转化膜的制备及耐蚀性能研究.中国稀土学报.2005,23(1):40～42
18陈长军,王茂才,刘一鸣.镁合金表面改性新技术.腐蚀科学防护技术.2004,16(4):215～217
19蒋永锋,翟春泉,郭兴伍,等.聚苯胺膜在AZ91镁合金表面的生长过程.材料导报.2003,17(4):70～72
20 P. Schmutz, V. Guillaumin, R.S. Lillard, et al. Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium. Journal of the Electrochemical Society. 2003, 150(4): B99～B110
21张津,孙智富,汪崧扬,等.镁合金表面热喷铝工艺及防腐性研究.表面技术.2003,32(3):8～9
22张津,孙智富.AZ91D镁合金表面热喷铝涂层研究.中国机械工程.2002,13(23):2057～2058
23张津,孙智富,叶宏.镁合金表面喷铝防腐蚀层的微观组织分析.材料保护.2003,36(6):17～18
24张永君,严川伟,王福会.镁阳极氧化膜微观结构和防护性能的比较.腐蚀科学与防护技术.2004,16(4):218～220
25 P I Butyagin, Ye V Khokhryakov. Microplasma systems for creating coatigs on aluminium alloys . Materials Letters. 2003, (57): 1748～1751
26 L Rama Krishna, K R C Somaraju. The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation. Surface and Coatings Technology. 2003, 163: 484～487
27 J.P. Schreckenbach, N. Meyer, G. Marx, et al. Strontium Hafnate Phases by Anodic Spark Conversion. Applied Surface Science. 2003, 205: 97～101
28薛文斌,邓志威.ZM5镁合金微弧氧化膜的生长规律.金属热处理学报.1998,19(3):42～45
29 P. Terleeva, A.I. Slonova, G.A. Markov. Electrochemical Microplasma Processes of Wear and Corrosion Resistant Coatings Formation on Parts of the Oil Equipment. Chemistry and Chemical Technologies. 2002: 344～346
30 Güntherschulze A, Betz H. Neue Untersuchungenüber die elektrolytische Ventilwirkung. Z. Phys. 1932, 78: 196～210
31 Güntherschulze A, Betz H. Die Elektronenstromung in Isolatoren bei extremen Feldstarken. Z. Phys. 1934, 91: 70～96
32 S. Ono, H. Kijima, N. Masuko. Microstructure and Voltage-current Characteristics of Anodic Films Formed Magnesium Alloy in Electrolytes Containing Fluoride. Materials Transactions. 2003, 44(4): 539～545
33 M. Boinet, S. Verdier, S. Maximovitch. Application of Acoustic Emission Technique for In Situ Study of Plasma Anodizing. NDT&E International. 2004, 37: 213～219
34 A.D. Pogrebnjak, Y.N. Tyurin. The Structure and Properties of Al2O3 and Al Coatings Deposited by Microarc Oxidation on Graphite Substrates. Technical Physics. 2004, 49(8): 1064～1067
35 L.S. Saakiyan, A.P. Efremov, A.V. Epelfeld. Further Development of Ideas of G.V. Akimov on the Surface Oxide Films and Their Effect on the Corrosion and Mechanical Behavior of Aluminum Alloys. Protection of Metals. 2002, 38(2): 186～191
36 D.I. Slovetskii, S.D. Terentev. Parameters of An Electric Discharge in Electrolytes and Physicochemical Process in An Electrolyte Plasma. High Energy Chemistry. 2003, 37(5): 310～316
37 G.A. Markov, G.V. Markova. Method for Forming Anodes of Electrolytic Capacitors. USSR, 526961. 2[P]. 1976―11-12
38 Yerokhin A L, Nie X, Leyland Aet a. Plasma elect rolysis for surface engineering. Surface and Coatings Technology. 1999, 122: 73～79
39 Kuhn A. Plasma anodizing of magnesium alloys. Metal Finishing. 2003, 101(9): 44～50
40 Beauvir, J acques. Oxidizing elect rolytic method for obtaining a ceramic coating at the surface of a metal. US, 6808613. 2[P]. 2004-10-26
41张文华,胡正前,马晋.俄罗斯微弧氧化技术研究进展[J].轻合金加工技术.2004,32(1):25～28
42李建中,邵忠财,田彦文,等.微弧氧化技术在Al、Mg、Ti及其合金中的应用.腐蚀科学与防护技术.2004,16(4):218～220
43 Zozulin A J, Bartak D E. Anodized Coatings for Magnesium Alloys. Metal Finishing. 1994, 92(3): 39～43
44王立世,蔡启舟等.国外镁合金微弧氧化研究状况.材料保护.2004,37(7):61～63
45刘耀辉,李颂.微弧氧化技术国内外研究进展.材料保护.2005,38(6):36～38
46梁军,郭宝刚,田军,等.氢氧化钾对镁合金微弧氧化的影响.材料保护.2005,38(4):12～14
47梁军,郭宝刚,田军,等.工艺参数对AZ91C镁合金生成微弧氧化膜层的影响.材料科学与工程学报.2005,23(2):262～265
48郝建民,陈宏,张荣军.电参数对镁合金微弧氧化陶瓷层致密性和电化学阻抗的影响.腐蚀与防护.2003,24(6):249～251
49刘君,谈政,甄华霞,等.AZ91D镁合金的微弧氧化研究.煤矿机械.2004,12:49～52
50姚美意,周邦新,王均安.电压对镁合金微弧氧化膜组织及耐蚀性的影响.材料保护.2005,38(6):7～10
51 X. Nie, C. Tsotsos, A. Wilson, et al. Tribological Evaluation of AISI 304 Stainless Steel Duplex Treated by Plasma Electrolytic Nitrocarburising and Diamond-like Carbon Coating. Wear. 2002, 253(9-10): 986～993
52 Allan Matthews, Adrian Leyland, Andrew Wilson. Plasma Immersion Ion Implantation as A Technique in Duplex and Hybrid Processing. Vacuum. 2003, 68: 57～64
53蒋百灵,张淑芬.镁合金微弧氧化陶瓷层耐蚀性的研究.中国腐蚀与防护学报.2002,22(5):300～303
54卫中领,陈秋荣,郭散聪,等.镁合金微弧氧化膜的微观结构及耐蚀性研究材料保护[J].2003, 36(10):21～23
55 S. Ono, H. Kijima, N. Masuko. Microstructure and Voltage-current Characteristics of Anodic Films Formed Magnesium Alloy in Electrolytes Containing Fluoride. Materials Transactions. 2003, 44(4): 539～545
56 V. Birss, S. Xia, R. Yue, et al. Characterization of Oxide Films Formed on Mg-based WE43 Alloy Using AC/DC Anodization in Silicate Solutions. Journal of the Electrochemical Society. 2004, 151(1): B1～B10
57 P. Schmutz, V. Guillaumin, R.S. Lillard, et al. Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium. Journal of the Electrochemical Society. 2003, 150(4): B99～B110
58焦树强,旷亚非.镁及其合金的腐蚀与阳极化处理.电镀与环保.2002,22(3):3～5
59 Albella.J.M, Montern I, Martine Duart J.M. Electron injection and avalancke during the anodic oxidation of tantalum . Electrochem.Soc. 1984, 131: 1101～1108
60 Schwartz M. Plasrna electrolysis for surface engineering. Proc.Amer, Electropplat.Soc. 1960, 47: 176～179
61 John S. Barium titrance films synthesiszed by an anodic oxidation based electrochemical method. Metal Finishing. 1982, 80(4): 47～50
62魏同波,田军.液相等离子体电沉积表面处理技术.材料科学与工程学报.2003,21(3):450～452
63 Wu Hanhua, Jin Zengsun, Long Beiyu. Charaterization of Microarc Oxidation Process on Aluminum Alloy. Chin. Phys. Lett. 2003, 20(10): 1815～1818
64 T.H. Teh, A. Berkani, S. Mato, et al. Initial stages of Plasma Electrolytic Oxidation of Titanium. Corrosion Science. 2003, 45: 2757～2768
65 F.A. Bonilla, A. Berkani, Y. Liu, et al. Formation of Anodic Films on Magnesium Alloys in An Alkaline Phosphate Electrolyte. Journal of the Electrochemical Society. 2002, 149(1): B4～B13
66 O.P. Terleeva, V.I. Belevantsev, A.I. Slonova. Types of Discharges in Electrochemical Microplasma Processes. Protection of Metals. 2003, 39(1): 50～54
2李卫平,朱立群.镁及其合金表面防护性涂层国外研究进展.材料保护.2005,38(2):41～45
3祁庆琚,刘永兵,杨晓红.镁合金的研究及其在汽车工业中的应用与展望.汽车工程.2002,24(2):94～100
4李德辉,董杰,曾小勤,等.高性能稀土镁合金研究进展.材料导报.2005,19(8):51～53
5郭旭涛,李培杰,刘树勋,等.稀土耐热镁合金发展现状及展望.铸造.2002,51(2):68～68
6郭旭涛,李培杰,曾大本.稀土在耐热镁合金中的应用.稀土.2002,23(2):63～63
7陈振华.镁合金.北京:化学工业出版社,2004:219～223
8 Anselm Kuhn. Plasma Anodizing of Magnesium Alloys. Metal Finishing. 2003, (9):44～50
9陈振华.变形镁合金.北京:化学工业出版社,2005:326～329
10张永君.镁及镁合金环保型阳极氧化表面改性技术研究:[博士学位论文].沈阳:中国科学院金属研究所,2003
11 J.E. Gray, B. Luan. Protective Coatings on Magnesium and Its Alloys-A Critical Review. Journal of Alloys and Compounds. 2002, 336: 88～113
12 Sundararajan G, Ramakrishna L. Mechanisms underlying the formation of thick aluminum coatings through the MAO coating technology. .Surface and Technology. 2003, 167: 269～277
13 Schreckenbach J, Schlottig F, Marx G, et al. Preparation and microstructure characterization of anodic spark deposited barium titanate films. J Mater Res. 1993, 13: 1437～1443
14 Gnedenkov S. V, Gordienko P. S, Sinnebryukhov S. L, et al. Antiscuff coatings obtained by micro-arc oxidation of titanium alloys. Russian Journal of Applied Chemistry. 2000, 73: 6～9
15边风刚,李国禄,刘金海,等.镁合金表面处理的发展现状.材料保护.2002,35(3):2～2
16 Yerokhin A L, Nie X, Leyland A, et al. Plasma electrolysis for surface engineering. Surface and Coating Technology. 1999, 122: 73～79
17许越,陈湘,吕祖舜,等.AZ91镁合金表面稀土转化膜的制备及耐蚀性能研究.中国稀土学报.2005,23(1):40～42
18陈长军,王茂才,刘一鸣.镁合金表面改性新技术.腐蚀科学防护技术.2004,16(4):215～217
19蒋永锋,翟春泉,郭兴伍,等.聚苯胺膜在AZ91镁合金表面的生长过程.材料导报.2003,17(4):70～72
20 P. Schmutz, V. Guillaumin, R.S. Lillard, et al. Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium. Journal of the Electrochemical Society. 2003, 150(4): B99～B110
21张津,孙智富,汪崧扬,等.镁合金表面热喷铝工艺及防腐性研究.表面技术.2003,32(3):8～9
22张津,孙智富.AZ91D镁合金表面热喷铝涂层研究.中国机械工程.2002,13(23):2057～2058
23张津,孙智富,叶宏.镁合金表面喷铝防腐蚀层的微观组织分析.材料保护.2003,36(6):17～18
24张永君,严川伟,王福会.镁阳极氧化膜微观结构和防护性能的比较.腐蚀科学与防护技术.2004,16(4):218～220
25 P I Butyagin, Ye V Khokhryakov. Microplasma systems for creating coatigs on aluminium alloys . Materials Letters. 2003, (57): 1748～1751
26 L Rama Krishna, K R C Somaraju. The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation. Surface and Coatings Technology. 2003, 163: 484～487
27 J.P. Schreckenbach, N. Meyer, G. Marx, et al. Strontium Hafnate Phases by Anodic Spark Conversion. Applied Surface Science. 2003, 205: 97～101
28薛文斌,邓志威.ZM5镁合金微弧氧化膜的生长规律.金属热处理学报.1998,19(3):42～45
29 P. Terleeva, A.I. Slonova, G.A. Markov. Electrochemical Microplasma Processes of Wear and Corrosion Resistant Coatings Formation on Parts of the Oil Equipment. Chemistry and Chemical Technologies. 2002: 344～346
30 Güntherschulze A, Betz H. Neue Untersuchungenüber die elektrolytische Ventilwirkung. Z. Phys. 1932, 78: 196～210
31 Güntherschulze A, Betz H. Die Elektronenstromung in Isolatoren bei extremen Feldstarken. Z. Phys. 1934, 91: 70～96
32 S. Ono, H. Kijima, N. Masuko. Microstructure and Voltage-current Characteristics of Anodic Films Formed Magnesium Alloy in Electrolytes Containing Fluoride. Materials Transactions. 2003, 44(4): 539～545
33 M. Boinet, S. Verdier, S. Maximovitch. Application of Acoustic Emission Technique for In Situ Study of Plasma Anodizing. NDT&E International. 2004, 37: 213～219
34 A.D. Pogrebnjak, Y.N. Tyurin. The Structure and Properties of Al2O3 and Al Coatings Deposited by Microarc Oxidation on Graphite Substrates. Technical Physics. 2004, 49(8): 1064～1067
35 L.S. Saakiyan, A.P. Efremov, A.V. Epelfeld. Further Development of Ideas of G.V. Akimov on the Surface Oxide Films and Their Effect on the Corrosion and Mechanical Behavior of Aluminum Alloys. Protection of Metals. 2002, 38(2): 186～191
36 D.I. Slovetskii, S.D. Terentev. Parameters of An Electric Discharge in Electrolytes and Physicochemical Process in An Electrolyte Plasma. High Energy Chemistry. 2003, 37(5): 310～316
37 G.A. Markov, G.V. Markova. Method for Forming Anodes of Electrolytic Capacitors. USSR, 526961. 2[P]. 1976―11-12
38 Yerokhin A L, Nie X, Leyland Aet a. Plasma elect rolysis for surface engineering. Surface and Coatings Technology. 1999, 122: 73～79
39 Kuhn A. Plasma anodizing of magnesium alloys. Metal Finishing. 2003, 101(9): 44～50
40 Beauvir, J acques. Oxidizing elect rolytic method for obtaining a ceramic coating at the surface of a metal. US, 6808613. 2[P]. 2004-10-26
41张文华,胡正前,马晋.俄罗斯微弧氧化技术研究进展[J].轻合金加工技术.2004,32(1):25～28
42李建中,邵忠财,田彦文,等.微弧氧化技术在Al、Mg、Ti及其合金中的应用.腐蚀科学与防护技术.2004,16(4):218～220
43 Zozulin A J, Bartak D E. Anodized Coatings for Magnesium Alloys. Metal Finishing. 1994, 92(3): 39～43
44王立世,蔡启舟等.国外镁合金微弧氧化研究状况.材料保护.2004,37(7):61～63
45刘耀辉,李颂.微弧氧化技术国内外研究进展.材料保护.2005,38(6):36～38
46梁军,郭宝刚,田军,等.氢氧化钾对镁合金微弧氧化的影响.材料保护.2005,38(4):12～14
47梁军,郭宝刚,田军,等.工艺参数对AZ91C镁合金生成微弧氧化膜层的影响.材料科学与工程学报.2005,23(2):262～265
48郝建民,陈宏,张荣军.电参数对镁合金微弧氧化陶瓷层致密性和电化学阻抗的影响.腐蚀与防护.2003,24(6):249～251
49刘君,谈政,甄华霞,等.AZ91D镁合金的微弧氧化研究.煤矿机械.2004,12:49～52
50姚美意,周邦新,王均安.电压对镁合金微弧氧化膜组织及耐蚀性的影响.材料保护.2005,38(6):7～10
51 X. Nie, C. Tsotsos, A. Wilson, et al. Tribological Evaluation of AISI 304 Stainless Steel Duplex Treated by Plasma Electrolytic Nitrocarburising and Diamond-like Carbon Coating. Wear. 2002, 253(9-10): 986～993
52 Allan Matthews, Adrian Leyland, Andrew Wilson. Plasma Immersion Ion Implantation as A Technique in Duplex and Hybrid Processing. Vacuum. 2003, 68: 57～64
53蒋百灵,张淑芬.镁合金微弧氧化陶瓷层耐蚀性的研究.中国腐蚀与防护学报.2002,22(5):300～303
54卫中领,陈秋荣,郭散聪,等.镁合金微弧氧化膜的微观结构及耐蚀性研究材料保护[J].2003, 36(10):21～23
55 S. Ono, H. Kijima, N. Masuko. Microstructure and Voltage-current Characteristics of Anodic Films Formed Magnesium Alloy in Electrolytes Containing Fluoride. Materials Transactions. 2003, 44(4): 539～545
56 V. Birss, S. Xia, R. Yue, et al. Characterization of Oxide Films Formed on Mg-based WE43 Alloy Using AC/DC Anodization in Silicate Solutions. Journal of the Electrochemical Society. 2004, 151(1): B1～B10
57 P. Schmutz, V. Guillaumin, R.S. Lillard, et al. Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium. Journal of the Electrochemical Society. 2003, 150(4): B99～B110
58焦树强,旷亚非.镁及其合金的腐蚀与阳极化处理.电镀与环保.2002,22(3):3～5
59 Albella.J.M, Montern I, Martine Duart J.M. Electron injection and avalancke during the anodic oxidation of tantalum . Electrochem.Soc. 1984, 131: 1101～1108
60 Schwartz M. Plasrna electrolysis for surface engineering. Proc.Amer, Electropplat.Soc. 1960, 47: 176～179
61 John S. Barium titrance films synthesiszed by an anodic oxidation based electrochemical method. Metal Finishing. 1982, 80(4): 47～50
62魏同波,田军.液相等离子体电沉积表面处理技术.材料科学与工程学报.2003,21(3):450～452
63 Wu Hanhua, Jin Zengsun, Long Beiyu. Charaterization of Microarc Oxidation Process on Aluminum Alloy. Chin. Phys. Lett. 2003, 20(10): 1815～1818
64 T.H. Teh, A. Berkani, S. Mato, et al. Initial stages of Plasma Electrolytic Oxidation of Titanium. Corrosion Science. 2003, 45: 2757～2768
65 F.A. Bonilla, A. Berkani, Y. Liu, et al. Formation of Anodic Films on Magnesium Alloys in An Alkaline Phosphate Electrolyte. Journal of the Electrochemical Society. 2002, 149(1): B4～B13
66 O.P. Terleeva, V.I. Belevantsev, A.I. Slonova. Types of Discharges in Electrochemical Microplasma Processes. Protection of Metals. 2003, 39(1): 50～54