About Anodizing/Anodizing line

Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal part.
Aluminium alloys are anodized to increase corrosion resistance and to allow dyeing(coloring),improved lubrication,or improved adhesion.However,anodizing does not increase the strength of the aluminium object.The anodic layer is nonconductive.

The anodized aluminium layer is grown by passing a direct current through an electrolytic solution,with the aluminium object serving as the anode(the positive electrode).The current releases hydrogen at the cathode(the negative electrode)and oxygen at the surface of the aluminium anode,creating a build-up of aluminium oxide.Alternating current and pulsed current is also possible but rarely used.The voltage required by various may range from 1 to 300 V DC,although most fall in the range of 15 to 21 V. Higher voltages are typically required for thicker coatings formed in sulfuric and organic acid.The anodizing current varies with the area of aluminum being anodized,and typically ranges from 30 to 300 amperes/meter²(2.8 to 28 ampere/ft²).

Aluminium anodizing is usually performed in an acid solution which slowly dissolves the aluminium oxide.The acid action is balanced with the oxidation rate to form a coating with nanopores,10-150 nm in diameter.These pores are what allow the electrolyte solution and current to reach the aluminium substrate and continue growing the coating to greater thickness beyond what is produced by autopassivation.However,these same pores will later permit air or water to reach the substrate and initiate corrosion if not sealed.They are often filled with colored dyes and/or corrosion inhibitors before sealing.Because the dye is only superficial,the underlying oxide may continue to provide corrosion protection even if minor wear and scratches may break through the dyed layer.

Condition such as electrolyte concentration,acidity,solution temperature,and current must be controlled to allow the formation of a consistent oxide layer.Harder,thicker films tend to be produced by more dilute solutions at lower temperatures with higher voltages and currents.The film thickness can range from under 0.5 micrometers for bright decorative word up to 150 micrometers for architectural applications.


In recent years,manufacturers of mobile phones and other 3C(Computer/Communication/Consumer Electronices)products,extensive use of aluminum alloy as a structural element of their products,so that aluminum anodizing prodess is widely used. 

 

Anodizing of aluminium alloy shell for 3C products process

Loading →Degreasing →Water Rinse →Alkaline Etching →Water Rinse →Black Film Stripping →Water Rinse →Chemical Polishing →Water Rinse →Surface Film Stripping Treatment  →Water Rinse →Anodizing →Water Rinse →Activation →Coloring →Water Rinse →Sealing →Water Rinse →Nitrate Dust Removing →Water Rinse →Sealing →Water Rinse →Nitrate Dust Removing →Water Rinse →Oven  Drying →Unloading 

 

KSDW®Anodizing Line