Method of producing a chromium-free conversion coating on a surface of an aluminium or aluminium alloy strip

摘要

In a method of producing an aluminium or aluminium alloy strip with a heat-seal lacquer on a first surface and an epoxide based stove lacquer on the second surface, a chromium-free conversion coating is produced on the first and second surface of the aluminium or aluminium alloy strip in a continuous production line before applying the hot seal lacquer and the stove lacquer, the chromium-free conversion coating is produced by
(A) a no-rinse process by treatment with a solution of silanes in a polar organic solvent, or
a no-rinse process by treatment with an aqueous solution of 5 to 10 wt.-% hexafluorotitanic acid (H 2 TiF 6 ) and 2.5 to 5 wt.-% hexafluorozirconic acid (H 2 ZrF 6 ), or
(B) a rinse process by treatment with an aqueous solution of < 1 wt.-% diammonium dimolybdate ((NH 4 ) 2 Mo 2 O 7 ) and 5 to 10 wt.-% hexafluorozirconic acid (H 2 ZrF 6 ).