The difference between China’s aluminum profile standards and Japanese and American standards

GB 5237.3-2008 “Aluminum Alloy Architectural Profile Part 3: Electrophoretic Paint Profile” is mainly based on GB/T 8013-2007 and is formulated with reference to JIS H8602-1992 in Japan and AAMA 612-02 in the United States. At the time of formulation, the performance requirements and indicators of the specification have reached or exceeded the Japanese JIS H8602-1992 rules, and the performance requirements such as hydrochloric acid resistance and mortar resistance have been increased based on the characteristics used in construction. However, the revision of JIS H8602 in Japan has stopped. The new version of JIS H8602-2010 is expected to have very large changes compared with JIS H8602-1992, and the performance requirements have been greatly improved, and the ISO proposal for the aluminum anodized electrophoretic coating composite film standard is in In the past few years, it has been revised and improved from time to time. This article will give a brief overview of the main differences between China’s GB5237.3-2008 specification and the Japanese JIS8602-2010 specification and the ISO proposal of China and Japan.

2.1 Weather resistance

Weather resistance is an important performance index of electrophoretic aluminum alloy profiles for construction. Japanese standards and ISO proposals divide the experimental time of xenon lamp artificially accelerated weather resistance into four levels of 350h, 1000h, 2000h and 4000h, while China’s national standard aluminum profiles will artificially accelerate xenon lamp weather resistance. The experimental time is divided into three gears of 1000h, 2000h and 4000h. Since our country’s standard mainly considers outdoor use, it is compared with the proposal of Japan and ISO. There is no test time of 350h. The other three gears are compatible with Japanese standards and ISO proposal requests. quite.

Although the three specifications have little difference in the weather resistance requirements of composite membranes, there are still differences in the environmental rules for the use of composite membranes in the three specifications. The third-grade composite membrane of China’s standard rules only regulates the weather resistance requirements of each grade, but the application environment of the composite membranes of each grade is not understood. In the Japanese JISH8602-2010 and ISO proposals, the application environment of each grade of composite membranes has stopped guiding clarification. It is recommended that the electrophoretic composite membrane with an experimental time of 350h be used in an indoor environment, and the electrophoretic composite membrane with an experimental time of 1000h should be used in a normal outdoor environment ( Such as ordinary cities, green areas and industrial areas), the electrophoretic composite membrane with an experimental time of 2000h is used in outdoor harsh environments (such as corrosive and degradable areas polluted by sea salt), and the electrophoretic composite membrane with an experimental time of 4000h Used in seaside areas, harsh outdoor environments and strong UV exposure areas. The author believes that the application environment recommended in the Japanese JISH8602-2010 and ISO proposals has certain practical significance and can guide customers to select composite film grades.

2.2 Combined corrosion resistance

Different from China’s standards, the Japanese JISH8602-2010 and ISO proposals specifically stipulate that the artificial accelerated weather resistance test of the fluorescent ultraviolet lamp should be stopped first, and then combined with the corrosion resistance request of the salt spray test. The author believes that there are mainly the following elements.

2.2.1 Operability elements

From an operational point of view, the weather resistance test inspection time is too long, often thousands of hours, many manufacturers do not have time and it is impossible to have so much time to wait for the inspection report, and choose other related performance tests with a shorter time.

2.2.2 Ideal elements

From an ideal point of view, when using a 313nm ultraviolet lamp to manually accelerate the weatherometer to stop the test, choose the test conditions that are closer to the natural situation, that is, the irradiation intensity is 30W/m2, 4h is dry, 4h is humid, the cycle stops for 240h, and then CASS is stopped. The experiment, the combined corrosion resistance experiment, can better reflect the application status of practice. Because aluminum doors, windows and curtain walls are not subject to ultraviolet light, they must also be corroded by natural acid rain, smoke, soil, bird droppings, detergents, etc.

2.2.3 Coating elements

From the point of view of the paint, 240h of UV exposure is equivalent to a brief aging experiment. If the long-carbon chain acrylic monomer with better stability or better is not selected, and the cost is simply reduced, this test is difficult to pass. In addition, the polymerized resin must have good light stability and not be degraded, that is, not powdered in nature. The author once saw windows made of electrophoretic profiles produced by a well-known aluminum factory in Shandong in a commercial house that has not yet been sold on a seaside in Shandong.

In order to eliminate this situation, during the production process, it is necessary to make monomers with different properties respond according to the request of reactivity ratio in the copolymerization process, and adjust the proportion of each monomer fed every hour so that it does not produce a polymerization reaction. The residual amount of free monomers in the polymer is small, and the molecular weight is average (the heating loss can be controlled within 3%), so as to improve the corrosion resistance and weather resistance of the coating film at the same time. Choosing an appropriate long-chain acrylate is good for light stability, and the molecular weight of the polymer can be larger, and the resulting resin will be in a self-emulsifying state. Corrosion resistance, weather resistance and mechanical properties will be improved, and the penetration rate can also be improved, so that the dependence of the coating on the co-solvent is greatly reduced. The reduction of organic solvents is beneficial to environmental maintenance (Japanese paint factory in Japan electrophoretic coating It is basically an emulsified paint).

2.2.4 Elements from a micro perspective

From a microscopic point of view, xenon lamps are often used, and their wavelength is generally selected between 340nm and 410nm (the peak value is 340nm), which also belongs to the category of ultraviolet rays. However, in terms of rays, the particle energy = hν, where h is Planck’s constant and ν is the frequency of the ray. In other words, the shorter the wavelength, the greater the energy of the ray particles, and the better the stability of the coating film can be detected in a short time. If the linked coating film is bombarded by high-energy particles without chain scission (pulverization), the subsequent CASS experiment will show excellent corrosion resistance. On the contrary, if the molecular chain breaks after 240 hours of ultraviolet radiation. (This is not easy to see in a simple weather resistance test), it will have a great impact on its corrosion resistance in the subsequent CASS experiment.

2.2.5 Relevant data provided by Japan

Although the new Japanese specifications do not make clear requirements for the thickness of oxide film and electrophoretic coating film, whether it is oxide film or electrophoretic coating film, if it is too thin, it is difficult to pass the combined corrosion resistance test. At the same time, this is also a newer and higher request for electrophoretic coatings, how to take a step forward in saving energy and improving performance.

2.2.6 Elements of the future development of coatings

From the perspective of the future development of coatings, weather resistance is an important performance index of aluminum alloy architectural profiles. However, due to the differences in the environment and geographic areas in which it is used, different specifications can be adopted, so that coatings can be selected in a targeted manner.

Polymers made of acrylic acid and its esters as raw materials have high weather resistance, which is mainly determined by monomers. It is composed of polymerization methods and has strong stability to light. If the monomer is selected properly, the coating film will have excellent gloss retention. This kind of resin has much better weather resistance than polycondensation polymers. As such a coating, it must also have excellent corrosion resistance. The key is to form the cross-linking of the coating. Using hexamethoxymethyl melamine as the cross-linking agent, it has good cross-linking during the curing process. , So that the coating film has high hardness, gloss, color (non-yellowing) and excellent weather resistance. In recent years, the appearance of cathodic electrophoretic coatings with better light resistance is also a good choice. Its corrosion resistance is better. It is constructed of polypolyamine resin and made of IPDI (isophorone isocyanate) or aliphatic isocyanate. The finished crosslinking agent has excellent weather resistance and can be made into CED. With CED, aluminum alloy oxidation is not used. Because the electrophoretic behavior is toward the cathode during the electro-stacking process, the oxide film will be partially or completely destroyed. However, this coating still has excellent corrosion resistance and weather resistance, and there are many People think that this should be the development trend of the architectural category.

Regarding the coating process, the use of electro-accumulation is an ideal method, which is beneficial to automated consumption and has high efficiency. The application rate of coatings is as high as 95% (the aluminum anode electrophoretic coatings consumed in China are generally 82%, and the efficiency reduction is mainly related to the viscosity of the coating solution. Related to the anti-interference performance), the quality of the consumer coating film is relatively stable. It is a film formed by ED. The process is that under the action of an electric field, it is first coated on the part with high current density. After the film is formed, the resistance becomes larger, and the film is not formed. The adjacent part becomes the part with high current density, and the coating is continued, so that each part of the workpiece constitutes a high resistance, and the coating film will not thicken after prolonging the ED time. Regarding the complicated geometric shape of the profile, it can be used in each part. The part gets the average film thickness of the coating, which is called the ED penetration rate performance, and makes it excellent in corrosion resistance, and also improves the weather resistance.

3 Other issues that need attention in the specification

3.1 Hardness

The hardness of the coating film is a fundamental performance index of the electrophoretic composite film. There are two main methods for testing the hardness of the aluminum alloy surface treatment film at home and abroad, one is the indentation hardness test, and the other is the pencil hardness test. Generally speaking, the indentation hardness is usually used to stop the detection of the thicker coating film, and the pencil hardness test is usually used to stop the detection of the thinner coating film. Due to the relatively thin film thickness of electrophoretic aluminum alloy profiles, the pencil hardness test is used in China’s GB5237.3-2008 standard and the ISO proposal to stop testing the hardness of the electrophoretic paint film (the Japanese standard does not regulate the hardness of the film). However, the performance indicators of the two specifications are somewhat different. The hardness of the composite membranes of grade A and B in our country’s standard rules should reach at least 3H, and the hardness of grade S composite membranes should reach at least 1H; while the ISO proposal rules all composite membranes have a hardness of at least 3H.

When using the pencil hardness test to stop the test, pay attention to the choice of the pencil. The experiment should choose the special pencil for the coating film hardness test to stop. The test result uses the hardness of the pencil to indicate the hardness of the coating film. In the pencil hardness experiment, the hardness and stability of the pencil used in the experiment have a greater impact on the results of the experiment. The hardness of the pencils consumed in various countries also has certain differences. Brand pencils and Japanese Mitsubishi pencils are relatively softer. If these two pencils must be compared, the Japanese Mitsubishi pencils are harder from a statistical point of view.

The hardness of the coating film is mainly related to the performance of the coating and depends on the degree of crosslinking of the curing. In addition, the thickness of the coating film has a great impact on the hardness. When the thickness of the coating film is relatively thin, the hardness is relatively higher.

3.2 Gloss

Neither our country nor the Japanese standard has a gloss stop rule. The ISO proposal stipulates a gloss test method, but its quality and data requirements are negotiated by both the supplier and the buyer. Gloss is usually measured with a 60-degree gloss meter. If it is more subdivided, a multi-angle gloss meter can be used to measure and distinguish between several angles. When measuring, it is requested that the inspected surface must be flat, and the flatness should be below 0.18.

3.3 Adhesion

China’s standards, Japanese standards, and ISO proposals all have rules on adhesion, and the indicators of the three specifications are all equivalent, and all require that the adhesion should reach level 0 (25/25). Adhesion has a great influence on the physical properties of the coating film. The effect of corrosion resistance should not be ignored. The cross-cut method is more commonly used. However, it is necessary to pay attention to the selection of the cross-cut device to ensure that the tool is sharp. The coating film can be scratched to expose the metal substrate. The secondary adhesion test after immersion is to simulate the impact on it after being washed by rain. If there is a lot of fall, it means that the coating film has not been completely bonded to the substrate material or has been swollen.

3.4 Salt spray corrosion resistance

There are usually three methods of salt spray corrosion resistance test, namely, neutral salt spray test (NSS test), acetic acid salt spray test (AASS test) and copper accelerated acetic acid salt spray test (CASS test), in which CASS test accelerates corrosion Sex is faster. The CASS experiment is a salt spray experiment that accelerates the destruction under the action of copper salt. This experiment must be done, especially in coastal subtropical areas.

The salt spray corrosion is quite serious under the operating conditions in the area. Nowadays, the environment is polluted.

Contamination issues have also increased requests for data preservation. China’s specifications, Japanese specifications, and ISO proposals all have requirements for salt spray experiments, and regulate the scope of application of different levels. However, it should be noted that China’s specifications only regulate the test time to two levels of 24h and 48h, while the Japanese specifications and The ISO proposal stipulates that the experiment time is 24h, 72h, and 120h. At the same time, it requests that the outdoor area with corrosion should reach the specification of 120h. The performance request is more stringent than the Chinese standard.

3.5 Alkali resistance

The requirements for alkali resistance in China’s specifications, Japanese specifications, and ISO proposals are basically the same. The alkali resistance test should be stopped at 20°C, because different temperatures have a great influence on the results. However, the experimental results collected by the author show that under the premise of complete curing, all coatings in our country can pass the alkali resistance test. If you are in a rainy, humid, hot and polluted area, you can think about stopping the second alkali resistance test, that is, do the boiling water resistance test first, and then do the alkali resistance test within one hour after drying. The results are very different. The different resins selected by the manufacturer will also have a great impact on the results.

3.6 Thickness of the composite membrane

According to the new Japanese regulations, the thickness of the oxide film should be above 5μm, and there is no requirement for the thickness of the electrophoretic paint film. In fact, as everyone knows, the big difference between electrophoresis and other coating methods is that there is no dead corner of the coating, and the entire oxide film can be evenly coated. During coating, the central resistance of the coating film becomes larger. Therefore, the paint particles will accumulate in the center of the small resistance, but if the oxide film is too thin, the oxide film itself will form a serious uneven resistance. The experiment shows that if you want to get an even electrophoretic coating film, the oxide film on the main decorative surface The thickness should be at least 6μm or more. Therefore, what I want to say is that although the Japanese regulations require the oxide film thickness to be 5μm or more, the classification should be stopped according to performance; but according to my understanding, the film thickness controlled by Japanese companies when they stop consumption in practice is above 8μm, which is also in line with the theory. explain. At the same time, we carefully analyzed the data of Mr. Katsuji Yajima and found that at least for now, if you want to pass the corrosion resistance test, the better data choice is 9+7. However, due to the uneven oxidation conditions and quality of electrophoretic coatings in Chinese factories, this data should be applied to China. We have no data to prove it. As for the thickness of the electrophoretic coating film, the new Japanese specification only stopped the performance request, which caused panic among Japanese coating manufacturers. Everyone should reduce the film thickness as much as possible under the condition that the coating film performance meets the requirements. And we know that the electrophoretic coating film Many of its properties, such as CASS, weather resistance, etc., have a lot to do with film thickness.

3.7 Natural weatherability

Regarding electrophoretic aluminum profiles, weather resistance is very important. Since the possibility of changing doors and windows in buildings is relatively small except for villas, we often request aluminum doors and windows to have the same life span as buildings. Both China’s GB5237.3-2008 specification and ISO proposal have rules for natural weather resistance, but the detailed request rules are not clear enough. The performance indicators and experimental methods of China’s regulatory rules are negotiated and affirmed by both the supplier and the demander. Although the ISO proposal stipulates the experimental methods for natural weather resistance, the performance indicators are requested to be negotiated and affirmed by both the supplier and the demander.

In fact, natural weather resistance is more capable of reflecting the durability of the product, and the artificial accelerated weather resistance tested in the laboratory can certainly reflect the weather resistance of the product to a certain level, but due to the rapid acceleration of the experiment, there is a certain amount of distortion. risk. For this reason, the author believes that China’s specifications should focus on the study of natural weather resistance. Although the natural weather resistance request is not suitable for quality inspection, the research and development of coatings still has practical significance.

4 summary

Of course, there are still some differences between the Chinese standard GB5237.3-2008 and the Japanese standard JIS8602-2010 and the ISO proposal. But we have reason to believe that with the development of industry and the spread of economic globalization, our country will pay more attention to improving quality in the formulation of regulations, reducing the difference with the norms of advanced countries, and even be able to take the lead and propose the so-called advanced countries today. There are no standard items and testing methods. Efforts to improve various standards. It constitutes an advanced standard that is more in line with China’s national conditions, and provides an even more favorable reference and legal basis for the development of China’s industry.