ã€China Aluminum Network】
1 Foreword Because hexavalent chromium may cause skin allergies, damage to hereditary genes, and inhalation may also cause cancer, it is now widely recognized as a cause of lung cancer. Therefore, there is a strict regulation on the content of Cr6+ in the EU's ROHS directive. The allowable content of hexavalent chromium (Cr6+) in electrical and electronic equipment is 0.1% (1000ppm). For this reason, the chromium-free processing process is being researched all over the world. Currently, the chromium-free passivation treatment mainly includes the inorganic passivation treatment and the organic passivation treatment. It is said that the corrosion resistance of the film obtained after some chromium-free passivation is close to or even exceeds the chromate passivation treatment in some aspects, and has a good future for development.
Chromium-free processing technology has been widely used in the electronics industry, and it is said that the effect is very good, but there are few engineering examples of non-chrome processing technology applied to aluminum alloy building profiles, and there are also some problems in engineering applications. , China aluminum alloy building profile production enterprises for the application of chromium-free processing technology has some reservations. In recent decades, China’s environmental protection requirements have become more and more stringent. Local governments have also issued some mandatory regulations for the control of Cr6+. As a manufacturer of aluminum alloy building profiles, they are faced with a huge demand for chromium-free products. pressure. In response to the government’s energy-saving emission reduction and industrial upgrading call, we will guide enterprises in upgrading their technology. Nanhai Aluminum Profile Industry Association held two “Aluminum Profile Chromium-Free Processing Technology Seminars†in South China Sea in August and September of this year. Surface treatment experts were invited to attend the meeting. During the meeting, the delegates attended the meeting on issues related to chromium-free processing. There was a lively discussion and we spoke enthusiastically. In the meeting, we can see that the performance of chromium-free products is a concern for everyone. In this paper, the chromium-free processing products and chromium treatment products were compared to test the performance of chromium-free pretreatment spray products to explore the feasibility of chromium-free treatment process.
2 Test section 2.1 Preparation of test samples A total of 11 tests were conducted on this special case test. The sample pretreatment process includes chromate treatment process, phosphorus-chromium treatment process, titanium-zirconium chromium-free treatment (abbreviated as chromium-free treatment) process, and silane non-chromium treatment (abbreviation as silane treatment) process. The treated sample and the phosphorous-chromated sample are processed according to the normal production process. The titanium-zirconium-based chromium-free treated sample is processed according to the process requirements of the titanium-zirconium-based chromium-free treating agent supplier, and the silane-treated sample is based on Process requirements provided by the silane treatment process development unit are processed. For the treatment of the titanium-zirconium non-chromium treatment sample and the silane treatment sample, we simulated the horizontal line soaking treatment and the vertical line spray treatment, and for the chromium treatment sample and phosphorus - Chromium treatment samples due to production practices proved that both the soaking and spraying treatment methods can achieve the desired results, so the subject test only uses the soaking method for sample preparation.
The spray treatment process of the sample includes powder spraying process and fluorocarbon paint spraying process. The powder coating includes flat powder powder coating and sand grain powder coating. The spray treatment of all samples was performed with normal product production. The spray treatment process was controlled according to the paint supplier's requirements.
2.2 Test Operation 2.2.1 Coating Adhesion 2.2.1.1 Dry Adhesion and Wet Adhesion: According to GB5237.5-2008 Adhesion Test Method, dry adhesion and wetness of powder sprayed coating and fluorocarbon paint spray coating Adhesion tests are then performed.
2.2.1.2 Boiling Water Adhesion: According to the provisions of GB/T9286 to make a grid, the spacing between the grid is 1mm, the sample is placed in a beaker and boiled for 1h, and a clean tile is placed at the bottom of the beaker. After the test, the sticky tape was used to test whether the sample was peeled off. It was rated according to the provisions of GB/T9286. The grade 0 was required to be qualified.
2.2.2 Salt spray corrosion resistance 2.2.2.1 AASS test The AASS test is to be carried out in accordance with the provisions of GB/T 10125 for the salt spray test, and then in accordance with the relevant provisions of GB 5237.4. The test solution was prepared as follows: Dissolve sodium chloride in distilled water at a concentration of 50 g/L ± 5 g/L, and add an appropriate amount of glacial acetic acid so that the initial pH of the solution is 3.0 to 3.1. Before the test, two intersecting lines deep to the metal substrate are drawn on the examined surface of the sample, and the line segments do not cross the diagonal. The test was conducted using a salt mist box of Shanghai Qishan Testing Equipment Co., Ltd. The test temperature was 35°C ± 2°C and the test time was set to 1000 hours.
2.2.2.2 NSS test The NSS test is carried out according to the provisions of the neutral salt spray test in GB/T 10125 and then inspected in accordance with the relevant provisions of GB 5237.5. The test solution was prepared as follows: Dissolve sodium chloride in distilled water at a concentration of 50 g/L ± 5 g/L. After the preparation, ensure that the pH of the solution is between 6.5 and 7.2. Before the test, two intersecting lines deep to the metal substrate are drawn on the examined surface of the sample, and the line segments do not cross the diagonal. The test was conducted using a salt spray box of Dongguan Quanti Detection Equipment Co., Ltd. The test temperature was 35°C±2°C and the test time was set to 4000h (since this report, the neutral salt spray test has not yet ended, so this time The actual test time for each sample will be listed in the test).
2.2.3 Damp heat resistance Damp heat resistance test is carried out according to the provisions of GB/T1740 and GB5237.5, and the test time is set to 4000h (due to this report, the heat and humidity resistance test is not yet over, so this test will be List the actual test time for each sample). The specific method of operation is: The sample is hung in the hot and humid test box of Dongguan Quanti Detection Equipment Co., Ltd. The test temperature is set to 47°C, the relative humidity is set to 96%, and then the continuous test is performed.
2.2.4 Machu Test This test refers to Qualicoat for testing. Two cutting lines with a width of about 1 mm were drawn on the sample using a knife. The test was then placed in a solution in Machuo (Mackey's solution: sodium chloride 50 g/L, glacial acetic acid 10 mL/L, hydrogen peroxide 5 mL/L, The pH value was 3.0-3.3). The test temperature was maintained at 37°C±1°C. After immersed for 24 hours, 5 mL/L of hydrogen peroxide was added. The sample was then immersed for 24 hours and then the sample was taken out and washed for evaluation.
2.3 Test results Tests performed in this test sample include: dry adhesion, wet adhesion, boiling water adhesion, AASS test, NSS test, hygrothermal test, and Machu test. The test results are shown in Table 1 below.
3 Analysis of test results (1) Dry adhesion, wet adhesion, and boiling water adhesion of chromate or phosphorus-chromatized samples 11 samples were tested, and all samples were 0; 13 samples were detected in the AASS test. The test results of all the samples have reached the specifications in GB5237.4-2008 and Qualicoat specifications; 11 samples have been tested in the NSS test; the samples are still under test, and all the samples have been tested for more than 1000 hours. The corrosion of the surface was very few, and some of the samples had no obvious corrosion; 11 samples were tested for damp-heat resistance. The samples were still under test. All the samples were tested for more than 1000 hours. None of the samples were tested. Significant corrosion occurred; a total of 4 samples were tested in the Machu test, and no obvious corrosion occurred in all samples, which meets the Qualicoat specifications.
(2) The dry adhesion, wet adhesion, and boiling water adhesion of the silane-treated samples were examined. Twelve samples were tested, and all of the samples were of grade 0; 12 samples were detected in the AASS test. The batch of samples was tested for 768 hours. At present, there are two serious corrosion samples, the remaining samples have reached the test results in GB5237.4-2008 and Qualicoat specifications; NSS test detected a total of 12 samples, the batch is still testing, all the current sample surface The corrosion was very few, and some samples had no obvious corrosion; a total of 12 samples were tested for resistance to heat and humidity. The batch of samples was still under test. All the samples were tested for more than 1000 hours, and all the samples did not appear. Significant corrosion; The Machu test detected a total of 12 samples, all of which did not show significant corrosion, meeting the Qualicoat specifications.
(3) 36 samples of titanium-zirconium non-chromatized samples were tested for dry adhesion, and all samples were of class 0; 33 samples were tested for wet adhesion; all samples were of class 0; boiling water adhesion was tested separately Of the 36 samples, 5 of them had the phenomenon of release film, the rest of the samples were 0, and the passing rate was 86.1%; 39 samples were detected in the AASS test, of which 22 had completed the 1000h test, and the results of all samples were tested. All of them meet the requirements of GB5237.4-2008 and Qualicoat specifications. There are 17 samples that have not yet completed the 1000h test. According to the assessment of GB5237.4-2008, there are currently 4 unqualified; the NSS test has detected a total of 32 samples. The batch of samples is still undergoing tests. At present, there are only two large bubbles appearing on the surface of one sample. The surface of the rest of the samples has little corrosion, and some of the samples have not yet shown significant corrosion; a total of 32 samples were tested for dampness and heat resistance. The batch of samples is still undergoing tests. At present, all samples have been tested for more than 1000 hours. No obvious corrosion has occurred in all samples. There are 24 samples detected in the Machu test, of which 3 samples are not judged by the Qualicoat specification. qualified The remaining samples are qualified, a pass rate of 87.5%.
(4) For the 10th test, the abnormal results of the chromium-free samples that were treated by the spray method were suspected to be caused by the unused time and the human factors during operation. Therefore, we use the same The 11th test was conducted on the spray process and it was found that the sample from the 11th test was much better than the spray sample from the 10th test without chrome treatment. At present, all the test results showed no abnormalities.
(5) For fluorocarbon paint spraying products, if the pretreatment process uses a titanium-zirconium chromium-free treatment process, the primer uses a chromium-free primer, and as a result, the two boiling water adhesion tests are found to be unacceptable.
4 Conclusions From the above test results, we can draw the following conclusions:
(1) Under the conditions of scientific production management, most of the titanium-zirconium-based chromium-free products should be able to achieve or approach the performance of conventional chromium-based and phosphorus-chromatized products.
(2) For fluorocarbon paint spraying products, if the pretreatment process uses a titanium-zirconium chromium-free treatment process, care should be taken when using primers with chromium-free primers to avoid unacceptable production.
(3) For the silane treatment process, relevant units are still in the test. Because the silane treatment process used in this experiment may not be an ideal process, the data listed in this article is only for reference. According to a chemical supplier in the United States, silane treatment products have good performance, so the silane treatment process may be another development direction that we are looking forward to.
1.8G Guided Wave Radar Level Meter
1.8G Guided Wave Radar Level Meter,High Precision Flow Rate Meter,1.8G Liquid Level Gauge,High Precision Flow Volume Meter
Jiangsu Pinpai Technology Co., Ltd. , https://www.jspingpa.com