Gold finish on aluminium
3 Aug 2004
BASF has patented a new process that makes it possible to obtain a realistic gold finish on aluminium surfaces.
In conventional processes, gold effects are obtained by anodising the aluminium and then applying the colour. Dyes are often used to colour the surface, but there are limitations on the performance of the dyes used to obtain gold effects.
The shade often appears too yellow or too brown, and the lightfastness of the dyes is not always up to standard.
The BASF process colours the aluminium using baths containing methanesulphonic acid.
'Much better results can be obtained if baths based on high purity methanesulphonic acid are used instead of dyes', explained Dr. Helmut Witteler, Head of Development and Applications Technology for Surface Finishing at BASF.
'Instead of dyes, finely divided metal crystals are deposited in the aluminium oxide layer. This results in a realistic gold finish', he added.
Another advantage is that the methanesulphonic acid process enables aluminium to be coloured up to 50% more quickly compared to other processes.
