process for electrolytic coloring of aluminium and aluminium alloys produced in anodisch semi

摘要

The invention discloses a process for electrolytically colouring anodic oxide layers on aluminium or its alloys by means of alternating current in electrolytes containing metal salt. The process comprises two stages, direct current being applied in the first stage and alternating current in the second stage and a notable feature is that, instead of direct current, a modified alternating current which contains a marked cathodic component is applied in the first stage and an off-time of 10 to 60 seconds is inserted between direct current and alternating current treatment, a longer time and/or higher voltage being employed in the second stage than in the first stage.