GB1301577A - - Google Patents

Abstract

1301577 Colouring anodised aluminium CEGEDUR G P 7 May 1970 [9 May 1969] 22038/ 70 Heading C7B Al or an alloy thereof, having an oxide layer with a thickness of 1 to 50 microns produced by anodisation, is coloured by successive treatment with alternating current in a plurality of different metal salt baths each containing a solution of a metallic salt in a concentration of from 1 to 500g/l at a pH of 1 to 5, at a temperature of from 18 to 50‹C, the duration of the treatment in each bath being from 5 seconds to 5 minutes, the current density being from 0À1 to 5 A/dm<SP>2</SP> and the voltage being from 5 to 80 volts. Before anodising, the Al or its alloy may be given a matt surface by pickling in NaOH and then HNO 3 or may be given a bright surface by mechanical polishing or by chemical or electrolytic action. The anodising may be in sulphuric or chromic acid at concentrations of 50-200 g/l using DC or AC. For the colouring the counter electrode to the Al for each bath may be formed by the metal of the metal salt or by stainless steel. The coloured layers may be sealed by boiling distilled water which may contain nickel acetate. In the examples the Al or Al alloy (a), anodising bath (b), and metal salts of the successive colouring baths (c and d) are as follows:- 1 (a) Al, (b) H 2 SO 4 , (c) CuSO 4 , (d) NiSO 4 . 2 (a) Al-Mg, (b) H 2 SO 4 , (c) NiSO 4 , (d) CuSO 4 . 3 (a) Al-Si-Mg, (b) H 2 SO 4 , (c) CuSO 4 , (d) NiSO 4 . 4 (a) Al, (b) unspecified, (c) Ag 2 SO 4 , (d) NiSO 4 . 5 (a) Ag Mg, (b) H 2 CrO 4 , (c) Ag 2 SO 4 , (d) CuSO 4 . 6 (a) Al-Si-Mg-Mn, (b) H 2 SO 4 , (c) CuSO 4 , (d) Ag 2 SO 4 .