Do you know the classification of aluminum pigments? Aluminum pigments are one of the commonly used specialty powders, also known as aluminum powder pigments, aluminum silver flakes, or aluminum silver paste. These pigments appear as flake-shaped powders and, compared to other pigments, possess unique properties such as excellent substrate coverage, floatability, and a metallic shimmer effect. As a result, they are widely applied in industries like anti-corrosion coatings, automotive paints, architectural coatings, and printing inks. Today, we’ll briefly introduce the classification of aluminum pigments.
I. Classification Based on Different Aluminum Pigment Surface Modifiers
Aluminum pigments are classified into four main categories based on their surface modifiers: floating aluminum pigments, non-floating aluminum pigments, water-based aluminum pigments, and resin-coated aluminum pigments.
The floating type refers to aluminum pigment particles that remain suspended within the vehicle, forming a film that floats on the surface of the coating layer after drying. In contrast, the non-floating type means the aluminum pigment particles do not exhibit buoyancy within the vehicle; instead, they become suspended and settle either in the middle or at the bottom of the dried film layer. Water-based aluminum pigments are characterized by their ability to disperse evenly throughout water-based coating systems while maintaining good corrosion resistance, making them less prone to "blooming" in such formulations. Resin-coated types involve chemically treating aluminum pigments, causing polymers to form a protective layer around the flaky aluminum particles. These coatings are particularly suited for applications requiring superior resistance to acids, alkalis, high temperatures, and electrical voltages.
II. Classification by Aluminum Pigment Particle Size
Aluminum pigments are classified into fine silver, fine shimmering silver, and coarse shimmering silver, depending on their particle size.
Fine silver refers to aluminum pigment particles with a particle size ranging from 3 to 14 μm, characterized by their fine texture, excellent whiteness, and superior opacity. Medium silver refers to aluminum pigment particles with a particle size between 15 and 30 μm, distinguished by their balanced particle size, offering both noticeable brightness and shimmering effects while still maintaining good opacity. Coarse silver refers to aluminum pigment particles with a particle size exceeding 30 μm, noted for their larger particle size, which delivers enhanced brightness and a more striking, eye-catching shimmer.
III. Classification Based on the State of Aluminum Pigments
Aluminum pigments are classified according to their physical state into aluminum silver powder (also known as flake aluminum powder), aluminum silver paste (aluminum paste), vacuum-plated aluminum suspension, and strip-shaped aluminum pigments.
Aluminum silver powder is produced by dry or wet ball milling, followed by a coating process to remove solvents, resulting in a solvent content of less than 5%. It is primarily used in powder coatings. Aluminum silver paste, on the other hand, is obtained via wet ball milling with a solvent content ranging from 30% to 40%, making it ideal for use in paints and inks. Vacuum-plated aluminum suspension refers to a process that first uses physical methods to create nanoscale aluminum films, which are then collected, broken down into nano-sized flake-shaped aluminum powder, and finally mixed with appropriate additives and solvents to form a mirror-like, nano-flake aluminum paste. This product contains 8–12% aluminum particles and is specifically designed for coatings or inks that demand high brightness or exceptional mirror effects. Lastly, strip-shaped aluminum pigment is made by removing excess solvent from aluminum silver paste, adding resins and additives, and extruding the mixture through an extruder. It typically features a resin content of 20–30% and a solvent content below 5%, making it suitable for applications in plastics or inks.
4. Classified according to the shape of aluminum particles
Aluminum pigments are classified, based on the shape of the aluminum particles, into "cornflake-shaped" irregular forms and "silver-dollar-shaped" regular forms.
Rough, irregular "cornflake-shaped" aluminum particles scatter light extensively, giving a diffusely reflective appearance. In contrast, the smooth surface of "silver dollar"-shaped aluminum particles produces specular reflection, resulting in a brilliant, highly reflective effect.
That's all for today's introduction to aluminum pigment classification. We'll be sharing more knowledge about aluminum pigments in future updates—thanks for your attention, and see you next time!
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