Abstract: The invention relates to a composition and a process for the treatment, more precisely the "post-treatment" of phosphatized metal surfaces, particularly when the surfaces must be subsequently covered with a coat of paint. It relates also to a process for the preparation of the composition and a concentrate useful for this preparation. The composition comprises an effective proportion of trivalent titanium compound and it is presented with an acid pH, the proportion of said compound being sufficient for the corresponding composition to confer on the treated metal surface a protection equivalent to that obtained with known chromatizing solutions. More particularly, the composition contains trivalent titanium at a concentration of 0.01 to 2 g/l, preferably from 0.2 to 0.6 g/l and has a pH of 2 to 7. Reducing means can be arranged to regenerate the trivalent titanium in the treatment solution continuously.