page_title: Alumina effect pigment
section_title: Production process
hierarchical_section_title: Alumina effect pigment / Production process
caption_attribution_description: English: Alumina flake production
context_page_description: An alumina effect pigment is a pearlescent pigment based on alumina. It is used for decorative purposes on paints and plastics, giving them a matte, metal-like appearance.
context_section_description: In the first step of the production process, Al₂O₃ (Aluminium oxide) flakes with a very smooth surface are formed. The flakes are produced using a crystal growth process. They are formed in the corundum structure (α-Al₂O₃). The desired flake shape is achieved by controlled crystal growth in the axial and equatorial directions. The color purity and transparency of the effect pigments obtained by coating the Al₂O₃ flakes with metal oxides can be attributed to the synthesis procedure yielding single-crystalline thin flakes 
  The coating of the alumina platelets with high-refractive metal oxides, such as with titanium dioxide and iron(III) oxide leads to strongly reflecting effect pigments. These pigments possess a strong glitter effect. The coating process is analogous to that used for metal oxide mica pigments except it starts from an aqueous suspension of Al₂O₃ flakes. The complete manufacturing process of pigments based on aluminum oxide platelets, consisting of the flake production and the coating with metal oxides is shown in Figure 1 
  For outdoor applications they are modified with an additional weather stabilizing surface treatment.
caption: Fig. 1: Pure aluminium oxide flakes
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