FREMGANGSMAATE VED ELEKTROLYTISK FARGNING AV ALUMINIUM OG ALUMINIUMLEGERINGER

摘要

The present invention provides an improvement in the process for electrolytically coloring aluminum or an alloy thereof comprising the sequential steps of anodizing, coloring and fixing. In accordance with the improvement, the coloring step is conducted under conditions wherein the ratio between the concentration of the sulphuric acid used and the concentration of the color-producing salt or salts used is from 70:1 to 15:1, the concentration of the sulphuric acid being about 15 g/l and the salts used being metal sulphates, and wherein the peak voltage applied is from 10 to 45 volts and the temperature is about 25 DEG C. and wherein at the beginning of the coloring step of the process, the voltage is increased from 0 up to the peak voltage in a progressive and controlled manner.