Some preparatory work need to be done to ensure that the surface of the aluminum coil clean. In order to prevent the residual vegetable oil and lubricant on its surface, which will affect the spraying and application.
Before forming, the aluminum coil should be treated as follows:
1.The aluminum coil can be cleaned with boiling water. The key of boiling water cleaning is to clean up the residual degreaser on the surface of the substrate to ensure that the residual can be dissolved in it and prevent the secondary pollution of the degreaser on the substrate. The application mode is mainly composed of bubble invasion and self spray cleaning. The strength of commonly used water body need not be too high, otherwise, the minerals in water will transform into mineralization spots on the surface of substrate.
2.Due to the rapid linear speed of dip coating, the commonly used degreaser has a high concentration. The typical degreaser has two components: caustic soda (NaOH), sodium carbonate (Na2CO3), sodium silicate (Na2SiO3) and polyphosphate. The hot alkali deoiling process is generally divided into two steps to ensure that the surface of aluminum coil substrate is clean and tidy, and the method of self spray cleaning is used.
3. Carry out stainless steel passivation. Passivation of stainless steel is to produce conversion film on the surface of plate by means of pressurized self spraying, dip coating or roller coating. In general, the way of pressurized self spraying is usually used, and the sludge caused by passivation liquid in the whole application process will block the nozzle, thus harming the actual effect of self spraying. Although the dip coating method can solve this problem, the passivation solution is widely used. The above two methods have to clean the unnecessary passivation solution with tap water in the operation process, which will cause the acquisition and cleaning problems of sewage. Roller coating is a better passivation treatment method, which has the advantages of uniform sizing, high cost performance and no need of washing. Generally, chromate / metal oxide type modifier is selected for aluminum alloy plate, which contains chromate, chromic acid, ammonium sulfate, curing accelerator chloride and molybdate. This kind of modifier must add ammonium sulfate, otherwise it can not be used to solve the problem of aluminum alloy plate for food and drink.
Post time: Oct-23-2020