Method for coating zinc die-cast parts, multi-layered coating for the protection of zinc die-cast parts, and coated zinc die-cast part

A method for coating zinc die-cast parts comprising the steps:

• i) treating the zinc die-cast parts with a first liquid containing at least one builder and at least one surfactant;
• ii) treating the zinc die-cast parts with a second liquid to form a first layer on a surface of the zinc die-cast parts, where the second liquid contains at least one chromium(III) complex and at least one sulfate;
• iii) treating the zinc die-cast parts with a third liquid to form a second layer on the first layer, where the third liquid contains inorganic nanoparticles;
• and
• iv) drying of the treated zinc die-cast parts,
• wherein the at least one sulfate in the second liquid is selected from the group consisting of magnesium sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, and combinations thereof, and
• wherein the chromium(III) complex is a chromium(III) fluoride complex.