THE USE OF TRIARYLMETHANE DYES ON ALUMINUM

Coatings have been formed on the surface of unanodised aluminium elect rolytically treated in an aqueous solution of tin sulphate and a triar ylmethane dye. The coatings produced had a good decorative appearance, good adhesion and were 3-5 mu m thick. The coloured films had excelle nt light fastness but poor resistance to corrosion resistance. The dye s showing the most promise for this application were CI Acid Blue 9 an d CI Acid Green 5. These dyes interfered in the current flow, in so do ing modifying the surface topography and the semiconductive properties of the superficial aluminium oxide film formed during the colouring t reatment. The dye fragmentation, cyclisation and dimerisation products derived during the electrolytic treatment resulted in the formation o f organotin compounds.