Chromate, Iridite, and Alodine Conversion coatings passivate the aluminum surface and protect the article from corrosion while retaining conductivity. These coatings can be used as adhesion promoters. The processes are sometimes referred to as chemical film.
Type I: Contains hexavalent chromium. Colors the article yellow.
Type II: Does not contain hexavalent chromium. Colors are typically clear with a blue tint.
The conversion coating can be applied across the entire surface area of a part or can be applied selectively only to certain areas. Conversion coatings are often applied in conjunction with hard anodizing coatings.
Conversion Coatings are used for applications requiring:
• Corrosion resistance (Typically Cl 1A)
• Enhanced bond strength for adhesives and other coatings. (Typically Cl 1A)
• Conductivity / Connectivity. (Typically Cl 3)
• Mil –STD-171, 7.3.1
• Mil –STD-171, 7.3.3
• AMS 2474
• ASTM B449
Can the electrical characteristics of the coating be varied?
Can one weld onto the surface of a conversion coating?
Yes. Using both shielded arc and spot welding.
What is Iridite and what is Alodine?
Both are conversion coatings. One is the brand name of the MacDermid Corporation. The other is the brand name of the Henkel Corporation