Golden yellow finish on aluminum

A. Your question is vague to me, Mr. Venkataraman. A yellow gold finish can be achieved with paint, with tinted lacquer, with electrophoretic coatings, with a chromate conversion coating, with a dyed anodized finish, with brass electroplating, with gold plating, with titanium nitride sputtering, and probably a number of other ways as well. A few of these finishes (electrophoretic lacquer, anodizing, and electroplating) would involve electricity applied in a bath. What are the components in question, and what is required of the finish besides looking "yellow gold" in color?

Thanks.

A. Hi, Suresh.

Yes, a simple chromate conversion coating (which does not use electricity) can be applied to aluminum for corrosion resistance and conductivity, and it is often a yellowish color. The steps usually involve alkaline non-etch cleaning, alkaline etching, and desmutting (to remove non-aluminum alloy materials) before the conversion coating.

These days many finishes must be RoHS compatible, and that yellow color comes from hexavalent chromium, so it is not used as much as formerly. There are trivalent chromate conversion coatings, but they are often colorless. You can see MIL-DTL-5541 [on DLA] for more information, or contact the major vendors of chromate conversion processes like Macdermid for the Iridite trade name, Henkel for the Alodine trade name, or Chemetall.

Good luck.

Regards,