Abstract: The present invention relates to a solution that is free of chromium in all its oxidising states, comprising: - at least one chemical oxidising compound, - at least one aluminium complexing agent, - at least one corrosion inhibiting compound, and -optionally, a chemical sealant compound, the solution having a pH in the range from 1 to 5. The present invention also relates to a method for treating a metal surface, comprising the application, on the surface, of a solution as defined above. The present invention additionally relates to a coating of a metal surface that can be obtained by the method for treating a metal surface as defined above, to a metal surface comprising the coating and to the use of the solution in an anti-corrosion treatment of a metal surface.