Method for activating a metal surface to be phosphated, preferably a galvanized steel sheet

摘要

The present invention relates to a method for activating a metal surface, in particular a coated steel sheet, preferably a galvanized steel sheet, prior to phosphating, in particular a coated, preferably electrogalvanized metal. The sheet (2 ′) contacts an activation bath (6) comprising activated particles dispersed in water, preferably based on phosphate and / or titanium. In order to reduce or eliminate the problem of poor adhesion of the surface coating to the suitably electrogalvanized, phosphated metal strip, the present invention should be added to the activation bath (6) At least one additive (A) is provided that inhibits or at least slows the aggregation of activated particles. As the additive (A), polyethylene glycol (PEG) and / or sodium stearate is preferably added. In a particularly preferred embodiment according to the method of the invention, the particle size distribution of the activated particles present in the activation bath (6) is determined and the activation bath (6) is replaced as a function of the particle size distribution of the activated particles. Or removed from the process. [Selection] Figure 1