Method for corrosion-protective serial surface treatment of metallic components

摘要

The present invention relates to a method for serial surface treatment of metallic components comprising aluminium surfaces, wherein an alkaline pretreatment is followed by a conversion treatment. According to the invention, the intention during the alkaline pretreatment is that a maximum value for the concentration of dissolved zinc is not exceeded, in order to ensure a sufficient quality of the corrosion-protective coating on the aluminium surface of the components following the surface treatment. In a preferred embodiment, the content of dissolved zinc is effectively held below the respective bath-typical maximum value of dissolved zinc by the addition of compounds constituting a source of sulphide ions. The functionality of the surface treatment can be additionally increased by likewise controlling the content of dissolved aluminium in the alkaline pretreatment such that, by adding compounds constituting a source for silicate anions, a threshold value for dissolved aluminium is not exceeded.