Definition and functions of chemical pretreatmentTaking advantage of the technique with chemical solution or solvent to have pretreatment towards the aluminum
surface can be effectively remove the greasy dirt、pollutants、natural oxide film of the original aluminum product
surface to have a wetting 、even、cleaning
surface.
1. Common process flow of chemical pretreatmentCommon process flow of chemical pretreatment includes many methods such as derosination、alkali washing、ash disposal、rough
surface preparation of fluoride and washing. Based on the application、the requirement of
surface quality of unsolved aluminum products, we can adopt different process flow of chemical pretreatment.
2. The principles and functions of derosinatiionGrease will have hydrolysis reaction to generate glycerol and rather higher fatty acid during acidic degreasing solution. With the help of a small amount of wetting agent and emulsifier, grease can be dissolved more easily and to achieve the better greasing effect. Greasing treatment can remove the grease and dust of the aluminum
surface, which makes the later alkali washing become comparable even.
3. The principles and functions of alkali washingPutting aluminum into alkaline solution whose major component is caustic soda to carry on
etch reaction helps remove the smudge on the
surface. To wipe off the natural oxide film on the aluminum
surface thoroughly will appear pure metallic matrix so that follow—up anticathode oxidation can be moving .
4. The principles and functions of removing fluorideAfter the alkali washing, the product
surface will attach intermetallic compound with a layer of insoluble caustic washing tank solution and its alkali washing product, which are layers of taupe or dark gray dusting. The goal of removing the dusting is that it can prevent the follow—up anticathode oxidation procedure bath solution from polluting.
5. The principles and functions of rough surface preparation of fluorideThe meaning of rough
surface preparation of fluoride is a kind of acid etching technique using fluoride ion to make the aluminum product
surface produce highly even and high density pitting corrosion, whose purpose is to eliminate the extrusion mark on the product
surface and to have a smooth one. However, due to its serious pollution to the environment, it hasn’t been promoted the use any more.