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Before the aluminum coil is rolled, some pretreatment work needs to be done to ensure the cleanness of the surface of the aluminum coil, so as to prevent the residual grease and lubricant on the surface from affecting the coating and use. The following aluminum coil processing factory will answer your questions:
1、 The aluminum coil can be cleaned with hot water. 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 mainly 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.
2、 Due to the fast linear speed of the precoating line, the degreasing agent used is generally of high concentration. Typical degreasing agents include 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 the aluminum coil substrate is cleaned, and spray brushing is often used.
3、 The aluminum coil shall be passivated. Passivation treatment is to make the passivator form a conversion film on the substrate surface by pressure spraying, dip coating or roller coating. Generally, pressurized spray is used. The sludge produced by the passivation liquid in the process of use often blocks the spray hole, thus affecting the spray effect. Although the dip-coating method solves this problem, the consumption of passivation solution is large.
The above two methods need to wash the excess passivation solution with water in actual operation, which will cause the problem of wastewater recovery and purification. Roller coating is a good passivation construction method, with the advantages of uniform coating, economic and practical, and no need for rinsing.
Generally, chromate/oxide type treatment agent is used for aluminum coil, 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 cannot be used to treat aluminum rolls for food and drink. Come to our website for more relevant matters http://www.f972.cn Ask!