GB684513A - A process for the production of silver-containing layers on aluminium and its alloys - Google Patents

Abstract

In a process for producing silver-containing layers on aluminium or its alloys, a firmly adhering oxide layer is produced on the metal, a dyestuff which reduces silver compounds to metallic silver is deposited in the pores of the oxide layer, and finally silver is precipitated in the pores by treatment with a solution of a silver salt. The oxide layer may be formed chemically or electrolytically. The dyestuff has preferably mordant properties and the following are stated to be suitable: derivatives of anthraquinone, flavone, xanthone, pyronin or oxazine or derivatives of benzene or naphthalene which have hydroxy or amino groups in the ortho or para positions. The silver solution may be ammoniacal silver nitrate. The silver may be converted to a halogen salt under darkroom conditions and used for printing photographic negatives. A resist may be painted on the oxide layer and the clear spaces impregnated with dyestuff and then silver or the dyestuff-impregnated layer may be painted with resist before treatment with the silver solution to produce a pattern. The metallic silver layer may be coloured red-dish to purple-brown by treatment with solutions of copper sulphate, potassium citrate, and potassium ferricyanide, sepia with solutions of uranium nitrate and potassium ferricyanide, or blue with solutions of potassium ferricyanide and iron citrate. The silver may be replaced by gold or platinum by treatment with solutions of salts of these metals. The silver may be built up with silver, gold, copper, nickel or chromium. As a final operation the pores in the aluminium oxide layer may be sealed by treatment with warm solutions of nickel or cobalt salts, or boiling water, or steam.