There are two main types of metallic pigments, aluminum and zinc.  The aluminum pigments are divided into two broad categories:  leafing grade and non-leafing grade.  The aluminum pigments are manufactured from pure aluminum (99.3-99.97% purity) and the particle is lamellar in shape (0.1-2 um in thickness and 0.5-200 um in diameter).  In the milling process stearic acid is used to give the leafing grade and have a bright silvery appearance.  These pigments orient themselves in a parrallel overlapping fashion in coating films.  the non-leafing grade are manufactured using oleic acid and they are either whiter / brighter or grayer / darker than the leafing grade.  The pigments are evenly distributed throughout the coatings, however they lack orientation.  These pigments are used extensively in automotive topcoats.

        Zinc is second metallic pigment.  There are two forms of zinc, powder and dust.  Only the Zinc dust is used in coatings.  The zinc dust is finer than the powder and is shperical.  The dust also has a light coating of zinc oxide.  Zinc rich coatings can be classified into two categories:  organic and inorganic.  The organic coatings can be applied over hand cleaned steel, while the inorganic coatings require sandblasting of the substrate.  Organic coatings are more flexible and more compatible with a variety of topcoats than inorganic coatings.  Inorganic coatings can provide excellent service without topcoating.
 

Pearlescent Pigments:

        Presently, mica pigments coated with titanium dioxide and/or iron oxide are the industrial important pigmetns.  They are safe, stable and environmentally acceptable for use in coating, cosmetics and plastics.  The pearlescent effect is produced by the behavior of incident light on the oxide coated mica; partial reflection from and partial transmission through the platelets create a sense of depth.  The color of the transparent light is complementary to the color of the reflected light.  As the ratio of TiO₂:Mica increases the colors change.  Click here to see.
 

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