Pretreatment of aluminum beverage cans

Largely unknown outside of a narrow circle of specialists, modern methods of chemical pretreatment are used in order to facilitate economical and high-quality painting of the politically controversial 'throwaway' aluminum beverage can. Colorless chromating on the basis of chromic acid and phoshporic acid has been supplanted for many years now by chromium-free processes which produce conversion coatings out of, e.g., zircon phosphate, only 0.002 to 0.005 μm thick. In order to achieve technological effects with such thin coatings, an innovative chemistry and a sophisticated process engineering are required.