Chemical Conversion Coatings

Pre-treatment of aluminum by conversion coatings

Chemical film coating is also referred to as Chem Film, Chromate Conversion, Iridite and Alodine. These are essentially the same process. Chemical  conversion coatings are deposited on aluminum by different methods such as dipping or spraying. The purpose is to form a continuous film, normally an oxide, which provides a good base for painting and adhesive bonding. Desirable properties of the conversion coatings are:

• Ability to form physical and chemical bonds to paints and adhesives

• Good resistance against hydration

• High stability over a wide pH range

• Corrosion protection of the aluminum substrate

The Alodine Product Family:

The name, “Alodine” is a registered trade name of Henkel Surface Technologies.  This family of compounds is formulated to provide a conversion coating on aluminum that will meet a military specification, MIL-DTL-5541F, which describes “Chemical Conversion Coatings on Aluminum and Aluminum Alloys,” and MIL-DTL-81706 that describes the processes certified for use.  These products are certified and listed in the “Qualified Products List,” QPL-81706-15.

Alodine T 5900 (Trivalent Chromium):

Alodine T 5900 is a trivalent chromium formulation that produces an iridescent blue to gold chromate conversion coating on aluminum alloys.   Neither the product compound nor the resulting coating contains hexavalent chromium.  It is generally recommended as an excellent base for organic finishes and adhesives.