A surface of aluminiferous metal is brought into contact at 25 to 65.degree. C. for 2 to 100 seconds with a surface treatment bath with a pH of 1.0 to 6.0 that contains phosphate ions, dissolved titanium and/or zirconium compounds, dissolved fluorine-containing anions, and a water soluble polymer in the following weight proportions: 1-100:1-50:1-200:1-200. This is followed by a water rinse and drying. The water soluble polymer has a chemical structure conforming to formula (I), in which each of X.sup.1 and X.sub.2 represents a hydrogen atom, a C.sub.1 to C.sub.5 alkyl group, or a C.sub.1 to C.sub.5 hydroxyalkyl group; each of Y.sup.1 and Y.sup.2 represents a hydrogen atom or a moiety "Z" that to formula (II) or (III), wherein each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 represents a C.sub.1 to C.sub.10 alkyl group or a C.sub.1 to C.sub.10 hydroxyalkyl group; the average value for the number of Z moieties substituted on each aromatic ring in the polymer molecules is from 0.2 to 1.0; n is an integer; and the average value of n for the total polymer is from 2 to 50. ##STR1##