Process and circuitry for the electrolytic coloring of anodised aluminium surfaces.

摘要

In a process for electrolytically colouring previously anodised objects made of aluminium or aluminium alloys in a colouring bath containing at least one metal salt which colours the aluminium oxide layer using an asymmetrical essentially sinusoidal alternating voltage made up of two separately regulable halfwave trains obtained by suitable rectification, it is intended to accelerate the colouring operation while at the same time ensuring uniform colouring. The process can be carried out, in particular, on a large scale with simple technical means. It makes it possible to apply an asymmetrical, essentially sinusoidal alternating voltage with separately regulable positive and negative halfwave to the colouring bath and maintain it.
This is achieved in that, for the purpose of colouring, there is applied to the colouring bath a regulable, asymmetrical and essentially sinusoidal alternating voltage of essentially constant frequency which is generated by first dividing at least one of two current paths originating from a voltage source path which delivers a symmetrical sinusoidal alternating voltage and ending in the colouring bath into two strands feeding the alternating voltage drawn from the voltage source in the latter to electrical engineering devices, in particular regulable transformers and directionally dependent converter valves or a diode and/or thyristor bridge, which renders the amplitudes of the positive and of the negative voltage halfwaves, and the ratio of said amplitudes independently variable and controllable, sets them to the required values and combines them to form the alternating voltage applied to the colouring bath by bringing together the strands and feeding them to the bath.