Effect pigments

An effect pigment based on an Al2O3 flake which comprises an Al2O3 flake coated with one or more layers of a metal oxide and/or a metal oxide mixture:

• wherein the ratio of the amount by weight of Al2O3 of the Al2O3 flake to the amount by weight of the metal oxide(s) of the coating layer(s) is in the range of from 27:73 to 83:17 based on the total weight of the effect pigment;
• wherein one or more layers of a metal oxide and/or a metal oxide mixture comprise one or more layers of metal oxides selected of TiO2, Fe2O3, Fe3O4, SnO2, ZrO2 or Cr2O3;
• wherein the thickness of each metal oxide and/or a metal oxide mixture layer on the Al2O3 flakes is 20-400 nm with the exception of any SnO2 layer, which has a layer thickness of 1-400 nm;
• wherein the effect pigment contains on the surface a protective layer containing at least one rare earth metal oxide, at least one metal oxide that is silicon, aluminum or zirconium or mixtures thereof, and an organic compound, and
• wherein the protective layer contains 0.2-2 wt. % of the at least one rare earth metal oxide, 0.2-2 wt. % of SiO2, 0.2-4 wt. % of Al2O3 and/or ZrO2 and 1-10 wt. % of the organic compound.