COLOURED PATTERN ON ANODIZED ALUMINIUM ARTICLE WITH SHADE DIFFERENCES

摘要

COLOURED PATTERN ON ANODIZED ALUMINIUM ARTICLE WITH SHAPE DIFFERENCE The specification relates to a method of forming a colored pattern on an article made of aluminum or aluminum alloy. The article is first anodically oxidised at a voltage from 10 to 120 volts to form a barrier layer. The barrier layer is then increased in thickness on those areas which, in the finished article, are to be colored by subjecting those areas to a second anodic oxidation at a voltage of from 15-200 volts, but at least 5 volts greater than the voltage applied in the first anodic oxidation. The article is electrolytically colored in an electrolytic metal salt bath at a voltage of from 5-75 volts either before or after the barrier layer formation. In this way a colored pattern can be formed on the article without the step of coloring the whole of the article uniformly, so the resulting pattern can be graduated in color or have partially colorless portions.