Pickling-activating solution for pre-treatment of aluminium-steel composites before electroless tin plating

摘要

The invention relates to an aqueous preparation for the pickling and activation of aluminum-steel composites prior to electroless dip tinning. Specifically, the invention provides pickling/activation solutions for the pretreatment of aluminum-steel composites prior to dip tinning which comprise sulfuric acid, hexafluorosilicic acid, at least one wetting agent, at least one transition metal cation and nitrate and/or nitrite ions.