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 non-coated aluminum foil, it should also have good shape and shape. coating properties.
1. Plate type of aluminum foil:
First of all, the production process of coated aluminum foil requires that the aluminum foil has a good shape, which is a prerequisite for the production of coated aluminum foil. The unit for measuring the shape index is I. The general coating production equipment’s requirements for the plate shape are within 20-40I. If it is greater than this value, a tension straightening system needs to be added before 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 of production. The air-conditioning production process also has higher requirements on the shape of the aluminum foil. The general heat exchange fin punching production line uses the vacuum suction cup method to transfer the aluminum foil. If the shape of the aluminum foil is not good and the surface is not flat, the vacuum suction method of the aluminum foil will not work normally. Therefore, the plate shape is not only an important technical index of coated aluminum foil, but also of uncoated aluminum foil.
2. Coating properties:
As mentioned above, there are many types of coated aluminum foils for heat exchange fins. At present, the coated aluminum foils used in the market are mainly hydrophilic aluminum foils. Therefore, only the coating performance indicators of hydrophilic aluminum foils are discussed here.
3. Coating thickness:
The thickness of the coating film on the surface of the aluminum foil is not strictly specified, and it is generally below 3/1m. Because the price of coatings is generally more expensive, the thinner the coating film thickness is under the premise of meeting the performance requirements, the lower the production cost. The thickness of the coating directly affects the 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 the adhesion fastness of aluminum foil to its surface coating. If the coating adhesion is too small, the surface coating 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. Coating adhesion can generally only be tested qualitatively. The main testing methods include abrasion resistance test, cross-cut test and cupping method.
5. Hydrophilic properties:
After the hydrophilic aluminum foil is used for a period of time, the hydrophilic properties of the surface will be affected by various environmental factors. Therefore, the hydrophilic performance is generally divided into the initial hydrophilicity and the hydrophilicity after the environmental resistance test. The quality of hydrophilic performance is mainly measured by the size of the angle a. The initial hydrophilicity requirements of general products are a<100, and the hydrophilicity requirements after the environmental resistance test are a<250. The contact angle a can be measured by using a special contact angle measuring instrument; it can also be calculated by the size of 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: First, alkali resistance. Since the lubricating oil on the surface of the heat exchange fin needs to be removed with an alkaline cleaning agent, the functional coating on the surface of the aluminum foil must have a certain alkali resistance. , Generally, it is required to soak in 20% NaOH solution for 3 minutes without foaming; the second is salt spray corrosion resistance, generally requiring no corrosion spots for 500 hours in a test condition of 35 ° C and 3% salt spray environment. The resistance to salt spray corrosion 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 higher requirements for the salt spray corrosion resistance of heat exchange fins. sex. This performance is also an important indicator to measure the weatherability of the heat exchanger fins.