As we all know the cleaning of aluminum coil surface is very important, so before aluminum coil is formed, some pee-treatment section is needed to ensure the surface of the aluminum coil cleaning. In order to avoid the existence of residual oil and lubricants impact on painting and use. It is mainly about 3 steps as follows.

First of all, the hot water can be used for cleaning aluminum coil. Hot water washing is mainly to clean residual decreasing agent of substrate surface, to ensure that residues can be dissolved, in case the decreasing agent cause secondary pollution to the substrate. The clean method are dip and spray scrub, so the water hardness is better not too high, otherwise, the minerals in the water will be generated ore spot on the substrate surface.

Secondly, as the pre-coating lines speed of hot alkali decreasing is fast, so the decreasing agent concentration is high, the typical decreasing agent contains sodium hydroxide (NaOH), sodium carbonate (Na2Co3), sodium silicate(Na2SiO3), phosphate and other components. Hot alkali decreasing process generally divided into two steps to ensure that the aluminum coil substrate surface is clean, and the method is multi-purpose spray scrub.

At last, the passivation treatment. Passivation treatment is using pressure spray, dip coating or roller methods to make passivating agent form conversion coating in the substrate surface. Generally with spray pressure, passivation sludge tend to plug nozzle, which influence the spraying effect. Dip coating method can solve the problem, but the consumption of passivation solution is bigger. The above two methods need to flush redundant passivation solution with water in practice, the problem of recovery and purification of waste water comes out, so roller coating is the best way of passive construction, it has advantages of uniform coating, economical and practical, do not need leaching, etc.