Reason analysis of color difference of 7075 aluminum alloy thick plate after sulfuric acid anodizing

doi:10.13251/j.issn.0254-6051.2024.12.047

Abstract

Abstract: In order to solve the problem of color difference caused by sulfuric acid anodizing of the 7075 aluminum alloy thick plate, optical microscope, scanning electron microscope, room temperature tensile testing and other methods were used to study the microstructure and properties of different color parts. The results show that the cooling rate is the main reason for the color difference of the sulfuric acid anodized film layer of the 7075 aluminum alloy thick plate. In the parts that can not reach the required cooling rate during solution treatment, a large number of micron-sized η phases are generated, and the film layer is formed unevenly during the sulfuric acid anodizing, resulting in a gray-black appearance. In the parts that can reach the required cooling rate during solution treatment, the microstructure is dominated by nano-scale η′ metastable precipitated phase, and the film layer is uniform during sulfuric acid anodizing, and the color is normally gray white. The gray-black part after sulfuric acid anodizing is re-heat-treated to regulate the microstructure, ant then the color of the film layer is returned to normal gray white.

Key words: 7075 aluminum alloy, sulfuric acid anodizing, solution treatment and aging, color difference

CLC Number:

TG146.21

Xun Jian, Yang Lei, Liu Meiling, Dong Xiaoyu, Ren Tianqi, Li Zhenghua, Cao Xiaorong, Zhou Liang. Reason analysis of color difference of 7075 aluminum alloy thick plate after sulfuric acid anodizing[J]. Heat Treatment of Metals, 2024, 49(12): 295-300.

References

[1]Zhang M, Liu T, He C, et al. Evolution of microstructure and properties of Al-Zn-Mg-Cu-Sc-Zr alloy during aging treatment[J]. Journal of Alloys and Compounds, 2016, 658: 946-951.
[2]Sun W, Zhu Y, Marceau R, et al. Precipitation strengthening of aluminum alloys by room-temperature cyclic plasticity[J]. Science, 2019, 363: 972-975.
[3]许志龙, 何林玥, 于乃川, 等. 典型阳极氧化铝合金在热带海洋大气环境下的腐蚀行为研究[J]. 电镀与涂饰, 2023, 42(20): 48-57.
Xu Zhilong, He Linyue, Yu Naichuan, et al. Study on corrosion behavior of typical anodized aluminum alloys in tropical marine atmosphere[J]. Electroplating and Finishing, 2023, 42(20): 48-57.
[4]何建平, 袁庆铭. 7075铝合金阳极氧化膜的结构和性能研究[J]. 机械工程材料, 2003, 27(9): 5-8.
He Jianping, Yuan Qingming. Microstructure and properties of anodic films of 7075 aluminum alloy[J]. Materials for Mechanical Engineering, 2003, 27(9): 5-8.
[5]Miera M S D, Curioni M, Skeldon P, et al. Modelling the anodizing behaviour of aluminium alloys in sulphuric acid through alloy analogues[J]. Corrosion Science, 2008, 50(12): 3410-3415.
[6]Okene S U, Abdullahi M, Gana A. Corrosion improvement of AA7075 through precipitation hardness and anodization[J]. Materials Today Proceedings, 2020, 38(4): 729-736.
[7]韩君利, 郝钢, 冮竹茵, 等. 某铝制件硫酸阳极氧化膜层灰黑色斑点问题技术分析及研究[J]. 中国设备工程, 2022(1): 12-13.
[8]李博. 2A12铝合金硫酸阳极氧化膜黑斑原因分析及改进方法[J]. 电镀与精饰, 2020, 42(2): 44-46.
Li Bo. Cause analysis and quality improvement of black patches of sulfuric acid anodic coating on 2A12 aluminum alloy[J]. Plating and Finishing, 2020, 42(2): 44-46.
[9]张华云, 任卫斌, 刘治国. 7A04CS板材阳极氧化表面局部发黑分析及解决措施[J]. 电镀与精饰, 2022, 44(7): 70-73.
Zhang Huayun, Ren Weibin, Liu Zhiguo. Analysis of local nigrescence on anodic oxide film surface of 7A04CS plate[J]. Plating and Finishing, 2022, 44(7): 70-73.
[10]冉林果. 7A04-T6热挤压铝合金棒材阳极氧化表面色差成因分析[J]. 铝加工, 2022(5): 14-17.
Ran Linguo. Analysis of color difference on anodized surface of 7A04-T6 hot extruded aluminum alloy bar[J]. Aluminum Fabrication, 2022(5): 14-17.
[11]赵洪凯. 铝及铝合金硫酸阳极氧化常见故障的原因及排除措施[J]. 材料保护, 2012, 45(12): 63.
[12]熊俊良. 铝合金硫酸阳极氧化膜斑点故障的原因分析[J]. 电镀与涂饰, 2020, 39(17): 1187-1189.
Xiong Junliang. Cause analysis on spot defect of anodization film formed on aluminum alloy from sulfuric acid[J]. Electroplating and Finishing, 2020, 39(17): 1187-1189.
[13]武平方, 刘冰, 张勤, 等. 铝合金硬质阳极氧化膜故障原因分析及对策[J]. 新技术新工艺, 2022(2): 77-80.
Wu Pingfang, Liu Bing, Zhang Qin, et al. Fault analysis and countermeasures of hard anodic oxide films of aluminum alloy[J]. New Technology & New Process, 2022(2): 77-80.
[14]董辉跃, 柯映林, 孙杰, 等. 铝合金厚板淬火残余应力的有限元模拟及其对加工变形的影响[J]. 航空学报, 2004, 25(4): 429-432.
Dong Huiyue, Ke Yinglin, Sun Jie, et al. Finite element method simulation for residual stress in quenched aluminum alloy thick-plate and its effect on machining distortion[J]. Acta Aeronautica et Astronautica Sinica, 2004, 25(4): 429-432.
[15]Wang Y, Wu X, Yue L, et al. Aging precipitation behavior and properties of Al-Zn-Mg-Cu-Zr-Er alloy at different quenching rates[J]. Transactions of Nonferrous Metals Society of China, 2022, 32: 1070-1082.
[16]张平, 李奇, 赵军军, 等. 7A52 铝合金中第二相分析及微区电位测试[J]. 中国有色金属学报, 2011, 21(6): 1251-1257.
Zhang Ping, Li Qi, Zhao Junjun, et al. Analysis of secondary phases and measurement of volta potential of 7A52 aluminum alloy[J]. The Chinese Journal of Nonferrous Metals, 2011, 21(6): 1251-1257.
[17]谭鑫, 徐芬, 钟叶清, 等. 室温停放时间对Al-Zn-Mg 合金组织与性能的影响[J]. 中国有色金属学报, 2021, 31(4): 815-825.
Tan Xin, Xu Fen, Zhong Yeqing, et al. Effect of parking time at room temperature on microstructure and properties of Al-Zn-Mg alloy[J]. The Chinese Journal of Nonferrous Metals, 2021, 31(4): 815-825.
[18]Ren J, Wang R, Feng Y, et al. Microstructure evolution and mechanical properties of an ultrahigh strength Al-Zn-Mg-Cu-Zr-Sc (7055) alloy processed by modified powder hot extrusion with post aging[J]. Vacuum, 2019, 161: 434-442.
[19]Miera M S D, Curioni M, Skeldon P, et al. The behaviour of second phase particles during anodizing of aluminium alloys[J]. Corrosion Science, 2010, 52(7): 2489-2497.
[20]Huang Y S, Shih T S, Wu C E. Electrochemical behavior of anodized AA6063-T6 alloys affected by matrix structures[J]. Applied Surface Science, 2013, 264: 410-418.
[21]Bozza A, Giovanardi R, Manfredini T, et al. Pulsed current effect on hard anodizing process of 7075-T6 aluminium alloy[J]. Surface and Coatings Technology, 2015, 270: 139-144.
[22]Sano T, Wakabayashi Y, Asoh H. Formation of hard anodic films on the 7075-T6 aluminum alloy by anodization in sulfuric acid and ethylene glycol[J]. SSRN Electronic Journal, 2023, 459: 1-8.
[23]秦会常, 贾波, 安柯, 等. 变形铝合金表面处理后浅色条纹产生的原因分析[J]. 精密成形工程, 2013, 5(3): 79-85.
Qin Huichang, Jia Bo, An Ke, et al. Analysis of the causes of light-colored stripe after surface treatment to wrought aluminum alloys[J]. Journal of Netshape Forming Engineering, 2013, 5(3): 79-85.
[24]刘诗超, 单俊杰. 铝合金锻件阳极氧化膜发黑缺陷控制技术研究[J]. 直升机技术, 2013(2): 46-51.
Liu Shichao, Shan Junjie. Research of control technology of aluminum alloy black color anodizing film defects[J]. Helicopter Technique, 2013(2): 46-51.