Chemical Film or “Chromate” is a chemical process that produces a protective chromate conversion film on aluminum and aluminum alloys. Chem-Film is a widely used process for the protection on aluminum. (It is also known by brand names Alodine® and Irridite®.) Chromate coatings can be used as a finial finish or can also serve as a base for paints, high performance topcoats, powder coats, lacquers, or as a base for rubber bonding. It can also be used in conjunction with masking of an anodized finish for conductivity properties.
Advantages of Conversion Coatings
- Economical & easy to use
- Can lend in extending service life of parts
- Minimize Surface Oxidation of Aluminum Parts
- Very Thin Coating: No Dimensional Change
- Primer for Paint Adhesion and other topcoats
At AOTCO, we offer both Hexavalent Chem-film
and, RoHS Hex-Free Chem-film coatings
Traditional Hexavalent chem-film can be applied on the aluminum surface with or without color to form a surface corrosion resistant film when it is dried. Typical color specification (class) for traditional hexavalent chromate is either “clear” or “gold”.
(per Mil-C-5541) Chemfilm “Classification” is determined by the exposure time of the aluminum part to the Chemical Film solution, where darker/more yellow coatings spend more time in the solution for greater corrosion protection.
ROHS chem-film does not contain Lead, Cadmium, Chromium (hexavalent or trivalent), Mercury or PBB/PBDE compounds, and is a more environmentally friendly option that produces a protective conversion coating on aluminum and it’s alloys.
(per Mil-DTL-5541) ROHS chem-film is always “clear” in color, but longer exposure to the solution can make the coat more visibly discernible in daylight, while providing corrosion protection.