铝合金表面稀土转化膜的制备工艺与成膜机理研究
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摘要
本文对铝及其合金表面稀土转化膜的制备工艺进行了初步研究,探讨了化学沉积转化膜的成膜机制和膜层裂纹的产生机理；以减少转化膜表面裂纹和改善其耐腐蚀性为目的,开发了磷酸盐后处理工艺,并对后处理的原理进行了研究。本文主要采取了以下的表征方法：利用扫描电子显微镜(SEM)、能谱仪(EDS)和涂层测厚仪来研究稀土转化膜的微观组织形貌、表面元素组成和膜厚；电化学阻抗谱、极化曲线和全浸腐蚀实验研究了试样表面稀土转化膜的电化学腐蚀行为和耐蚀机理。
利用正交实验确定了化学沉积成膜的最佳工艺参数。通过分析化学沉积过程中的膜层厚度、膜层单位面积质量、表面微观形貌和表面元素组成随沉积时间的关系,进一步研究了不同成膜工艺参数(稀土盐浓度、高氯酸钠的浓度、氧化剂过氧化氢的浓度、成膜时间和溶液的pH值)对稀土转化膜的影响。提出了化学沉积过程转化膜的成膜和裂纹形成机理：首先在溶液中发生的是铝的氧化和过氧化氢的还原过程,之后随着氢氧根离子的增多,靠近试样表面的溶液pH值逐渐升高,通过一系列反应最终形成了氧化铈转化膜,最后由于膜层的脱水会导致膜层开裂。
采用正交实验优化了化学沉积转化膜的磷酸盐后处理工艺,分析了不同后处理工艺参数(磷酸钠浓度、溶液温度、pH值和反应时间)对最终成膜的影响。实验结果表明,化学沉积稀土转化膜在经过磷酸盐后处理后,通过物质的转化形成了新的磷酸铈水合物,膜层的抗开裂性和耐蚀性能获得了很大的提高。
This thesis is aimed at the preparation technology of REM (rare earth metal) conversion coating on the aluminum and its alloy. The mechanism of the growth of spontaneous deposited conversion coatings and the formation of cracks on the surface of the coatings were discussed. For purpose of reducing the cracks on the conversion films and improve the corrosion resistance of these films, phosphate post-treatment process was developed. The theory of the post-treatment was studied. In this paper, characterization methods used mainly included:The microstructure, element composition and thickness have been examined by scanning electron microscopy (SEM), energy spectrometer (EDS) and coating thickness gauge. The corrosion behavior and corrosion mechanism of the substrate with conversion coating were evaluated by polarization curves, electrochemical impedance spectroscopy (EIS) and corrosion test.
The technical parameter of spontaneous deposited conversion coating was optimized by orthogonal tests. The analysis on the relationship between the thickness, mass per unit area, the micro-morphology, the element composition of the conversion coatings and the deposited time, further research on the effects of technical parameters (concentrations of rare earth salts, concentrations of sodium perchlorate, concentrations of oxidizer H2O2, immersion time and pH value of solution). The spontaneous depositing process theory about the formation of conversion films and crack initiation was proposed. At first, the deposition mechanism involves both the oxidation of aluminum and the reduction of hydrogen peroxide in the reactions. Then, the generation of hydroxide ions results in a pH increased near the surface of the substrate, which causes the formation of cerium oxide conversion coating by a series of reactions. At last, after the formation of the film, some cracks induced by dehydration of the coating will appear.
The optimum technical parameter of phosphate post-treatment was obtained by orthogonal tests. The effects of technical parameters (concentrations of sodium phosphate, temperature, treating time and pH value of solution) in post-treatment process were studied in detail. The experimental results showed that after spontaneous deposited Rare Earth conversion coating was post-processed, converted the structure of deposited coatings into hydrated cerium phosphate structure, the number of cracks was reduced and corrosion resistance was improved a lot.
利用正交实验确定了化学沉积成膜的最佳工艺参数。通过分析化学沉积过程中的膜层厚度、膜层单位面积质量、表面微观形貌和表面元素组成随沉积时间的关系,进一步研究了不同成膜工艺参数(稀土盐浓度、高氯酸钠的浓度、氧化剂过氧化氢的浓度、成膜时间和溶液的pH值)对稀土转化膜的影响。提出了化学沉积过程转化膜的成膜和裂纹形成机理：首先在溶液中发生的是铝的氧化和过氧化氢的还原过程,之后随着氢氧根离子的增多,靠近试样表面的溶液pH值逐渐升高,通过一系列反应最终形成了氧化铈转化膜,最后由于膜层的脱水会导致膜层开裂。
采用正交实验优化了化学沉积转化膜的磷酸盐后处理工艺,分析了不同后处理工艺参数(磷酸钠浓度、溶液温度、pH值和反应时间)对最终成膜的影响。实验结果表明,化学沉积稀土转化膜在经过磷酸盐后处理后,通过物质的转化形成了新的磷酸铈水合物,膜层的抗开裂性和耐蚀性能获得了很大的提高。
This thesis is aimed at the preparation technology of REM (rare earth metal) conversion coating on the aluminum and its alloy. The mechanism of the growth of spontaneous deposited conversion coatings and the formation of cracks on the surface of the coatings were discussed. For purpose of reducing the cracks on the conversion films and improve the corrosion resistance of these films, phosphate post-treatment process was developed. The theory of the post-treatment was studied. In this paper, characterization methods used mainly included:The microstructure, element composition and thickness have been examined by scanning electron microscopy (SEM), energy spectrometer (EDS) and coating thickness gauge. The corrosion behavior and corrosion mechanism of the substrate with conversion coating were evaluated by polarization curves, electrochemical impedance spectroscopy (EIS) and corrosion test.
The technical parameter of spontaneous deposited conversion coating was optimized by orthogonal tests. The analysis on the relationship between the thickness, mass per unit area, the micro-morphology, the element composition of the conversion coatings and the deposited time, further research on the effects of technical parameters (concentrations of rare earth salts, concentrations of sodium perchlorate, concentrations of oxidizer H2O2, immersion time and pH value of solution). The spontaneous depositing process theory about the formation of conversion films and crack initiation was proposed. At first, the deposition mechanism involves both the oxidation of aluminum and the reduction of hydrogen peroxide in the reactions. Then, the generation of hydroxide ions results in a pH increased near the surface of the substrate, which causes the formation of cerium oxide conversion coating by a series of reactions. At last, after the formation of the film, some cracks induced by dehydration of the coating will appear.
The optimum technical parameter of phosphate post-treatment was obtained by orthogonal tests. The effects of technical parameters (concentrations of sodium phosphate, temperature, treating time and pH value of solution) in post-treatment process were studied in detail. The experimental results showed that after spontaneous deposited Rare Earth conversion coating was post-processed, converted the structure of deposited coatings into hydrated cerium phosphate structure, the number of cracks was reduced and corrosion resistance was improved a lot.
引文
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[2]于兴文,曹楚南,林海潮等.铝合金表面稀土转化膜研究进展.中国腐蚀与防护学报,2000,20(5)：298～306
[3]陈道琪,范洪远,陈志文等.稀土在铝合金表面处理中的应用及研究进展.表面技术,2007,36(3)：58～60
[4]许越,陈湘,吕祖舜等.金属表面稀土转化膜的研究进展.稀土,2002,23(3)：58～62
[5]林肇琦.有色金属材料学.沈阳：东北工学院出版社,1986.68
[6]刑淑仪.铝合金和钛合金.北京：机械工业出版社,1987.35
[7]戴起勋.金属材料学.北京：化学工业出版社,2005.186
[8]朱祖芳.铝合金阳极氧化与表面处理技术.北京：化学工业出版社,1999.58-86
[9]朱祖芳.有色金属的耐腐蚀性及其应用.北京：化学工业出版社,1998.126～135
[10]孙跃,胡津.金属腐蚀与控制.哈尔滨：哈尔滨工业大学出版社,2003.3-10
[11]胡津.晶须增强铝复合材料的腐蚀行为研究：[博士学位论文].哈尔滨：哈尔滨工业大学,2002
[12]沈海军,郭万林,吕志国.NaCl溶液中LC9铝合金应力腐蚀特性的实验研究.腐蚀与防护,2002,23(5)：38
[13]任广军,赵春英.铝合金应力腐蚀裂纹内电化学行为.沈阳工业学院学报,2002,21(2)：110-113
[14]任广军,季雅芳.铝合金应力腐蚀裂纹内氯离子的分部.沈阳工业学院学报,1995,(4)：41
[15]朱日彰等.金属腐蚀学.北京：冶金工业出版社,1989.234
[16]孙宝德等.铝合金抗大气腐蚀表面处理.腐蚀与防护,1999,20(1)：24～30
[17]罗耀宗,巴烽翔.铝的化学氧化工艺探讨.上海电镀,1989,(4)：28～31
[18]胡忠良,马承银,潘春跃.亲水涂料的研究进展.江苏化工,2001,29(5)：14～17
[19]丰濑喜久郎.热交换器用铝散热器材.公开特许报.昭60-103[9],1985-06
[20]鲛写义弘.高亲水性涂料.公开特许报.昭63-258966,1988-10
[21]山田胜芳.铝及铝合金底材表面处理用水溶性组成物.公开特许报.昭62-2536741985-11
[22]周爱娟.铝亲水抗蚀有机膜的制备及亲水性表征.沈阳化工学院学报,1996,(1)：21～24
[23]程长进.耐蚀材料与环境.腐蚀与防护,1998,19(4)：147～150
[24]李凤梅,钱鑫源,李金桂.稀土在航空工业中的应用现状与发展趋势.材料工程,1998,(6)：10～14
[25]Hinton B R W. The inhibition of aluminum alloy corrosion by cerium coatings. Met. Forum, 1984; 7(4):211
[26]Arnott D R. Auger and XPS study of cerium corrosion inhibition on 7075 aluminum alloy. Applications of Surface Science,1984; 22-23(1):236
[27]Arnott D R. Cerium conversion coatings for the corrosion protection of aluminum. Met. Forum,1986; 9(3):162
[28]Hinton B R W. The inhibition of Al alloy corrosion by rare earth metal cations. Corrosion Australas,1985; 10(3):12
[29]Anortt D R. Cationic film-forming inhibitions for the corrosion protection of Al 7075 alloy in chloride solutions. Mater. Perform,1987; 26(8):42-47
[30]Mansfeld F. Pitting and surface modification of silicon carbide aluminum. Corrosion Sci, 1987,27(9):997
[31]Mansfeld F. Surface modification of Al/15%SiC metal matrix composites in molton salts containing CeCl3. Surface coating technology,1996,86-87:449
[32]Hughes A E, Gorman J D, Paterson P J K. The characterization of Ce-Mo based conversion coating on aluminum alloys part Ⅰ. Corrosion Sci.,1996,38(11):1957-1976
[33]Mamsfeld F. The Ce-Mo process for the development of a stainless aluminum. Mater. Sci. Forum.1992,111-112:191
[34]Chen C, Mansfeld F. Corrosion protection of an A16092/SiCp metal matrix compostites. Corrosion Sci,1997,39(6):1075
[35]李久青,等.铝合金表面四价铈盐转化膜及其耐蚀性. 腐蚀科学与防护技术,1996；8(4)：271
[36]李久青,等.铝合金表面稀土铈转化膜. 北京科技大学学报,1995；17(6)：584
[37]李久青,等.铝合金稀土转化膜处理对LC4合金耐SCC性能的影响. 腐蚀科学与防护技术,1996；8(2)：139
[38]于兴文等.见：第十届全国缓蚀剂学术讨论会论文集. 华中理工大学,1997：97
[39]石铁等.铝合金表面电解沉积稀土转化膜工艺研究. 电镀与涂饰,2005；24(6)：22
[40]田清波等.稀土铈转化膜在高氯离子溶液中的缓蚀作用. 材料保护,2005,38(5)：5
[41]曹楚南,张鉴清.电化学阻抗谱. 北京：科学出版社,2002：21-25
[42]Campestrini P, Terryn H, Hovestad A. Formation of a cerium-based conversion coating on AA2024.:relationship with the microstructure. Surface and Coatings Technology 176(3)(2004)365-381
[43]Stoffer O J, O'Keefe J T. Cerium-based spontaneous coating process for corrosion protection of aluminum alloys. US Patent,2004/0028820 A1, Feb.12,2004
[44]巩方玲,黄明智.明胶表面或性的研究. 明胶科学与技术,2000,20(3)：123-129.
[45]Pinc W, Geng S. Effects of acid and alkaline based surface preparations on spray deposited cerium based conversion coatings on Al 2024-T3. Applied Surface Science, 2009.255(2009):4061-4065
[46]Scholes F H, Soste C. The role of hydrogen peroxide in the deposition of cerium-based conversion coatings. Applied Surface Science,253(2006):1770-1780
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