The present invention relates to a method of cleaning pretreatment of ferrous components that have been joined by welding, in which residues from the welding operation are removed from the surface of the component and, in this way, subsequent wet-chemical conversion treatments are enabled so as to produce defect-free coatings. For cleaning pretreatment, the component is contacted with an aqueous sulfuric acid etchant which comprises amino alcohols, ethoxylates and/or propoxylates of fatty alcohols having 6 to 12 carbon atoms in the alcohol and iron ions, and is effective without the presence of fluorides. In a further aspect, the present invention encompasses an aqueous acidic etchant for cleaning pretreatment of ferrous components that have been joined by welding.