What is the Processing Work Before Forming Aluminum Coils

Before forming the aluminum coil, some pre-treatment sections need to be done to ensure the cleanliness of the surface of the aluminum coil. To avoid the presence of residual oil and smoothing agents on its surface, which may affect the painting and application. So, before forming the aluminum coil, it needs to be pre treated in the following aspects.

Firstly, it is recommended to use hot water to wash the aluminum coil. If the hot water scrubber cleans up the residual degreaser on the surface of the substrate to ensure that these residues can dissolve, in order to prevent these degreasers from forming secondary pollution on the substrate. The application methods are mostly immersion and spray brushing. The hardness of the water used should not be too high, otherwise minerals in the water will form mineral spots on the surface of the substrate.

Secondly, due to the fast pre coating line speed, the degreaser used for hot alkali degreasing usually has a higher concentration. Typical degreasers include sodium hydroxide (NaOH), sodium carbonate (Na2Co3), sodium silicate (Na2SiO3), phosphate and other components. The hot alkali degreasing process is usually divided into two steps to ensure that the surface of the aluminum coil substrate is washed clean, and spray brushing is often used.

Again, passivate it. Passivation treatment is the process of forming a conversion film on the surface of the substrate by means of pressure spraying, immersion coating, or roller coating. Usually, pressurized spraying is used, and the sludge generated by the passivation solution during use often congests the spray hole, thereby affecting the effectiveness of the spraying. Although the immersion coating method addresses this issue, the amount of passivation solution used is relatively large. Both of the above methods require water to clean the excess passivation solution in essential operation, which can lead to wastewater recovery and purification problems. Roller coating is a good passivation construction method, with advantages such as average coating, economic applicability, and no need for rinsing. Aluminum plates usually use chromate/oxide type treatment agents, which contain chromate, chromic acid, phosphoric acid, and promoters fluoride and molybdate. This type of treatment agent must be added with phosphoric acid, otherwise it cannot be used to treat aluminum plates for food and beverages.