A liquid concentrate for the preparation of chromating baths without six-valence chromium content, for the passivation of zinc electroplated coatings deposited from weak acid and alkaline non-cyanide as well as cyanide zinc plating baths. After the application, a bright and bluish layer has been formed which strengthens the overall corrosion durability of zinc coatings. The chromating bath is able to run within broad range of operation times and, consequently, is convenient for the passivation in both automatic and hand-operated plating lines. The composition of the agent ensures the durability of the bath against its pollution with iron ions. The bath itself features severalfold increased life in comparison with the six-valence chromium-based baths..