[China Aluminum Network] 1 Introduction In order to obtain better corrosion resistance, the general aluminum alloy anodic oxide film has to be sealed. The sealing process is divided into normal temperature sealing (low temperature sealing), medium temperature sealing, boiling water sealing, high temperature steam sealing and so on. Compared to other sealing methods, medium temperature sealing has the advantages of non-fluorine, fast sealing speed, no discoloration, and low cost. It is widely used in the industry.
According to the requirements of the national standard GB5237.2-2008, the weight loss of the sealed hole after the sealing of the profile 120h shall not be greater than 30mg/dm2. Photovoltaic aluminum film thickness requirements higher (≥ 15? M), after the average temperature sealing hole treatment, the general after 120h aging can make the sealed hole weight loss, it is difficult to meet the delivery requirements. Especially in dry weather conditions (the relative humidity of the company's warehouses in December and January is 40-60%), after the aging time (120h) specified in GB5237.2-2008, it is still difficult to guarantee the qualified seal loss.
In order to explore whether the sealing process can be guaranteed by the common medium-temperature sealing process under dry conditions, the effect of different sealing agents on the sealing effect was compared in this paper. In order to overcome the effects of the drying environment, shorten the aging time, and improve the quality of the sealing hole, the company improved the sealing process at medium temperature, that is, increased hot pure water washing. This article then determined the preferred conditions for hot pure water washing by orthogonal test.
2 Test section 2.1 Test 1
2.1.1 Material: The base material is a photovoltaic profile produced by the company with the award number 6063. The sealing agent is selected from the sealing agent A currently used by the company and the sealing agent HY and the sealing agent of well-known brands on the market. HH.
2.1.2 Process: Degreasing—washing—alkaline erosion—two times washing—neutralizing—two times washing—anodizing—two times washing—medium temperature plugging—two times washing.
2.1.3 Process parameters of key processes 2.1.3.1 Anodizing: Free sulfuric acid 170g/L, aluminum ion 13.0g/L, bath temperature 18°C, current density 1.3A/dm2, oxide film thickness 18μm.
2.1.3.2 Medium temperature sealing hole: Nickel ion is 1.2g/L, PH value is 5.7, temperature is 55°C, time is 1μm/min.
2.1.4 Test method: After an anodized profile on the production line, 18 pieces of sample with a length of 5 cm are cut into three different plugging solutions for the medium temperature sealing test.
2.1.5 Medium temperature sealing hole test For the objective comparison, the sealing agent A, HY and HH are uniformly formulated into 3 kinds of sealing solutions according to the process conditions of 2.1.3.2. The above 18 profiles were divided into 3 groups of 6 blocks each, which were sealed in 3 different sealing fluids for 18 minutes. After the sealing is complete, wash twice with tap water and let it dry naturally.
2.1.4 Sealed weight loss test After sealing the profile, the sample is stored in the company's warehouse (relative humidity 40-60%). After each group of samples were aged for 2 hours, 72 hours, and 120 hours, the GB/T 8753.2-2005 nitric acid pre-soaked phosphoric chromic acid method was used to measure the weight loss of the plugging.
2.2 Test 2
2.2.1 Process flow: According to the 2.1.2 process flow, a hot pure water wash is added later.
2.2.2 Test method: After the anodized and medium temperature plugged profiles are cleaned on the production line, 9 pieces of sample with a length of 5 cm are cut into hot pure water at different temperatures and taken out at intervals.
2.2.3 Orthogonal test: Take the temperature and time of hot pure water treatment as process parameters, select three different levels for each parameter, do orthogonal test, and determine the optimal parameters for hot pure water treatment. Sealed hole test was done after 2 hours of sealing.
3 Results and discussion 3.1 Comparison of sealing effect of different sealing agent In the dry environment, the sealing weight loss data measured at different aging times after treatment with different sealing fluids are shown in the following table:
Table 1
QQ screenshot 1.jpg
It can be seen from Table 1 that in the dry environment (relative humidity of 40% -60%), after the aging for 120 hours, the sealing pore weight loss of the samples treated with the three sealing fluids is not enough. After the sealing is completed at medium temperature, the profiles are generally placed for a period of time and are aged using the moisture in the air, and the drying environment slows down the aging. It can be seen that in the dry environment, the ordinary medium temperature sealing process does not guarantee the sealing quality of high-thickness oxide profiles (such as photovoltaic oxidation profiles).
3.2 Process conditions for hot pure water treatment The temperature and time of hot pure water treatment are used as process parameters. Three different levels are selected for each parameter and orthogonal tests are performed.
Table 2 horizontal factor table QQ screenshot 2.jpg
Table 3 Orthogonal test and results QQ screenshot 3.jpg
As can be seen from Table 1, the samples without heat-pure water treatment had a loss of 386-429 mg/dm2 after the sealing was completed. From Table 3, after the treatment with hot pure water, the aging is basically not carried out, and the weight loss of the plugging hole can also be greatly reduced.
It can be seen from the orthogonal test that when the temperature factor is selected at level 3, and the time factor is selected at level 3, the obtained sample is sample 9. The weight loss of the sealing hole is small, but the appearance is ash, and the time is as long as 16 minutes. The efficiency is not high. When the temperature factor is set to level 2 and the time factor is set to level 2, the sample obtained is sample 5, and the weight loss of the plugging hole is close to the sample 9, and the appearance is not ash. Therefore, we determined that the preferred process parameters for hot pure water treatment are: temperature 70°C, time 12 min.
4 Conclusion 4.1 In the dry environment, the ordinary medium temperature sealing process can not ensure the quality of the sealing of high-thickness oxide profiles (such as photovoltaic oxidation profiles).
4.2 The method of adding hot pure water washing after sealing in the middle temperature can accelerate aging, improve sealing quality and shorten delivery time.
4.3 The best process parameters for hot pure water treatment are: temperature 70°C, time 12min.
References [1] Wei Qingan. Study on the strengthening of aging process of aluminum profile oxide film after sealing at low temperature [J]. Light Alloy Processing Technology, 2004, Vol32, No 11:37-38
[2] Feng Gao, Li Cuiling, Liu Chuanxi, Yang Jun, Lan Lin, Ouyang Gui.Temperature Sealing Technology of Anodic Oxidation Film on Aluminum Alloy[J].Journal of Materials Protection,2011,Vol44,No.9:38-39
[3] Zhu Zufang. Anodizing and Surface Treatment of Aluminum Alloys [M]. Beijing: Chemical Industry Press, 2004: 226-232

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