New attractive finishes for architectural and decorative anodized aluminum: Fid-Bau Portal

New attractive finishes for architectural and decorative anodized aluminum

Dalla Barba, W.

This pqper reports on two new technologies for producing attractive new finishes on anodized architectural aluminum, which are the subject of patents. The first of these represents an approach to the production of a fine uniform finish on architectural extrusions, which reduces caustic soda consumption by up to 75 % and minimizes the problems associated with effluent treatment and sludge removal. As well as these advantages, the technique developed eliminates defects such as die lines, scratches, etc., thus improving yields and reducing operating consts. A second major development is that of a new electrolytic coloring system by means of which grey, blue, green, red and purple can be obtained from the same electrocoloring bath. This multi-colour process modifies the barrier layer with a specially developed current source and selectively 'electrodeposits' tin in the pores of the oxide film. Whereas the 'interference colors' previously developed required a second phosphoric acid anodizing step, the new technique uses only a sulfuric acid electrolyte. In conjunction with a computer-controlled power source for the coloring process, the reproducibility of the colors obtained is of a very high order. Using the above developments as complementary processes attractive uniform matt shades are obtained which differ from those normally produced by conventional anodizing and coloring methods, or by painting or powder coating.