Coated aluminum foil is formed after surface treatment on the basis of non-coated aluminum foil. In addition to the chemical composition, mechanical properties and geometric dimensions required by the above-mentioned non-coated aluminum foil, it should also have good shape and coating properties.
1. The shape of the aluminum foil
First of all, the production process of coated aluminum foil requires the aluminum foil to have a good shape, which is a prerequisite for the production of coated aluminum foil. The unit to measure the plate type index is I. General coating production equipment requires a plate shape within 20-40I. If it is greater than this value, a tension straightening system needs to be added in front of the coating equipment. Generally, the aluminum strip running route of the coating equipment is long, and there are many processing procedures and guide rollers. Therefore, if the tension straightening system is not equipped, once the plate shape is not good, it is easy to fold during operation, resulting in failure to produce. The air conditioner production process also has higher requirements on the shape of the aluminum foil. Generally, the production line of heat exchange sheet punching uses vacuum suction cups to transfer aluminum foil. If the shape of the aluminum foil is not good and the surface is uneven, the vacuum suction method of aluminum foil will not work normally. Therefore, the plate shape is not only an important technical indicator of coated aluminum foil, but also non-coated aluminum foil.
2. Coating performance
As mentioned earlier, there are many kinds of coated aluminum foils for heat exchangers. The coated aluminum foils used in the market are mainly hydrophilic aluminum foils. Therefore, only the coating performance indicators of hydrophilic aluminum foils will be discussed here.
3. Coating thickness
There is no hard rule on the thickness of the coating film on the surface of the aluminum foil, and it is generally below 3/1m. Because the price of coatings is generally more expensive, the thinner the coating film thickness is controlled under the premise of meeting the performance requirements, the lower the production cost. The thickness of the coating directly affects the various performance indicators of the coating, so the coating thickness on the surface of the aluminum foil is required to be uniform.
4. Coating adhesion
Coating adhesion is an indicator of how fast an aluminum foil is bonded to its surface coating. If the coating adhesion is too small, the coating film on the surface of the coated aluminum foil will easily fall off during further processing and use, which will seriously affect the weight of the coated aluminum foil. Therefore, the stronger the coating adhesion, the better. Generally, coating adhesion can only be detected qualitatively, and its main detection methods include abrasion resistance test, scratch test and cupping method.
5. Hydrophilic properties
After the hydrophilic aluminum foil is used for a period of time, the hydrophilic performance of the surface will be affected by various environmental factors. Therefore, the hydrophilic performance is generally divided into the initial hydrophilic performance and the hydrophilic performance after the environmental resistance test. The quality of hydrophilic performance is mainly measured by the size of a angle. The initial hydrophilicity requirement of general products is a<100, and the hydrophilicity requirement after the environmental resistance test is a<250. The contact angle a can be measured by using a special contact angle measuring instrument; it can also be calculated from the area occupied by a certain volume of water droplets on the surface of the aluminum foil.
6. Corrosion resistance
Corrosion resistance is mainly reflected in three aspects: one is alkali resistance. Since the lubricating oil on the surface of the heat exchange plate needs to be removed with an alkaline cleaning agent, it is required that the functional coating on the surface of the aluminum foil must have a certain degree of alkali resistance. , It is generally required to soak in 20% NaOH solution for 3 minutes without foaming; the second is salt spray corrosion resistance, generally in the test condition of 35 oC, 3% salt spray environment requires 500 hours without corrosion spots. The salt spray corrosion resistance is directly related to the service life of the heat exchange fins. In coastal areas, due to the high salt content in the air, there are high requirements for the salt spray corrosion resistance of the heat exchange fins; the third is the heat and humidity resistance performance, that is, the corrosion resistance of long-term storage at a certain temperature and humidity. sex. This performance is also an important indicator to measure the weather resistance of heat exchanger fins.