1995 Volume 81 Issue 9 Pages 906-911
A film exhibiting interference colors is formed on stainless steel when immersed in a hot solution containing chromic and sulfuric acids, and the applied process is known as the "INCO" method. In this method, the driving force of the coloring reaction is mainly caused by the thermal energy, and the reaction should be performed at elevated temperature (about 80°C). The reproducibility of colors obtained is very poor since it is very difficult to terminate the coloring reaction immediately, to maintain high temperature, and to treat such aggressive solution. Therefore, the coloration of stainless steel is expected to take place at room temperature. In the present study, the coloring reaction was carried out in a chromic and sulfuric acid solution by applying alternating potential pulses at room temperature, and a relatively large-sized electrolytic cell was used to aim an industrialization. The uniformity of the colored film was sensitively dependent on the distribution of current rush in the solution. The sort and brightness of the colors thus produced stood well in comparison with those obtained by the conventional coloring at high temperature.
