Alodine:

Alodine, IRIDITE, chem-film refers to a chemical conversion coating & Clear, protective, tarnish-resistant chromate film on silver:
Iridite 14 is a chemical process, which produces a clear to yellow corrosion-resistant film on aluminum and its alloys. The film can be used as a final finish or it can be dyed various colors using Iridite Dyes. The Iridite 14 coating is an ideal base for paints and lacquers and can also be used as a base for rubber bonding. Iridite 14 powder is dissolved in water to make the working solution, which can be applied by dip, brush, swab or spray. Iridite 14 can also be used to produce a clear, protective, tarnish-resistant chromate film on silver. It is very economical to use and has a number of advantages over treatments normally used to provide corrosion protection and tarnish resistance to silver. The Iridite 14 film is practically colorless, causes no dimensional change, and can be easily soldered. Its electrical contact resistance is quite low. Iridite 14 in contrast with other protective chemical treatments for aluminum has a minimum effect on the electrical characteristics for either high- or low frequency work. (Iridite 14) is qualified under MIL-DTL-81706, Class 3, Form II, Method C and Class 1A, Form II, Method A, B, C. This specification qualifies products for use in conforming to MIL-DTL-5541