来源：http://www.jndclyyxgs.com 发布时间：2021-07-29 14:35:50
Before the aluminum coil is rolled, some pretreatment sections need to be done to ensure the cleanness of the surface of the aluminum coil. To avoid residual grease and lubricant on the surface, which will affect the coating and use. Therefore, the aluminum coil should be pretreated in the following aspects before forming.
1、 Hot water can be used to clean the aluminum coil. Hot water cleaning is mainly to clean the residual degreasing agent on the surface of the substrate to ensure that these residues can be dissolved, so as to prevent these degreasing agents from causing secondary pollution to the substrate. The use methods are mostly immersion washing and spray brushing. The hardness of the water used should not be too high, otherwise the minerals in the water will form mineral spots on the surface of the substrate.
2、 Due to the fast line speed of precoating, the degreaser used for hot alkali degreasing generally has a high concentration. The typical degreaser contains sodium hydroxide (NaOH), sodium carbonate (Na2CO3), sodium silicate (Na2SiO3), phosphate and other components. The hot alkali degreasing process is generally divided into two steps to ensure that the surface of aluminum coil substrate is cleaned, and spray brushing is often used.
3、 Passivate it. Passivation treatment is to form a conversion film on the surface of the substrate by means of pressurized spraying, dip coating or roll coating. Generally, pressurized spraying is used. The sludge generated during the use of passivation liquid often blocks the spray hole, thus affecting the spraying effect.
Although dip coating solves this problem, the consumption of passivation solution is large. In practice, the above two methods need to wash the excess passivation solution with water, which will produce the problem of wastewater recovery and purification. Roll coating is a passivation construction method, which has the advantages of uniform coating, economy and practicality, no leaching and so on. Chromate / oxide treatment agent is generally used for aluminum plate, which contains chromate, chromic acid, phosphoric acid and accelerator fluoride and molybdate. This kind of treatment agent must be added with phosphoric acid, otherwise it can not be used to treat aluminum plates for food and beverage.