TENDENECY OF MATERIAL :-

Aluminium is known for it’s tendency of undergoing natural oxidation forming a thin layer of aluminium oxide on the surface.

NEED OF CLEANING -

PRESENCE OF OIL AND/OR LAYER OF ALUMINIUM OXIDE ON IT’S SURFACE.

Aluminium has a tendency to undergo natural oxidation forming a thin layer of aluminium oxide on the surface. Apart from this, commonly known process of anodizing also leaves layer of aluminium oxide under the influence of electric current. This is not a good base to apply powder or any other coating. Hence, it must be removed before powder coating.

Apart from this, there may be oil on the surface which may have come during fabrication process. This must be removed to have proper bonding of powder coating.

NEED OF CONVERSION COATING -

TO PREVENT FURTHER OXIDATION OF CLEANED ALUMINIUM SURFACE.

PRECLEANING OF ALUMINIUM

This include :

• Alkaline Cleaning & Acidic Cleaning
• Strong alkaline cleaners
• Mild alkaline cleaners

The aluminium material is very sensitive to alkaline attack. There for alkaline cleaners are milder for aluminium than for mild steel. However, if there is anodizing layer on aluminium, caustic soda based strong alkaline cleaner has to be used. However, this leaves black smut on the surface. To remove this aluminium is deeped in weak bath nitric acid.