Copper-zinc alloy pigments, commonly known as gold bronze pigments, are the scientific foundation of the gold bronze pigment industry. These flake-form metallic pigments are produced from copper-zinc alloys, with the ratio of copper to zinc determining the color shade—from greenish gold to reddish copper. Understanding the composition, production, and performance of these alloys is essential for formulators seeking to achieve specific metallic effects.

Understanding Copper-Zinc Alloy Pigments

Gold bronze pigments are typically composed of copper-zinc alloys, with a copper content ranging from approximately 70% to 95%, balanced by zinc. Small amounts of other metals may be added to inhibit oxidation and improve stability. The pigments are produced by the attrition of finely divided, usually atomized, alloy particles, resulting in flake-like particles with a high aspect ratio.

Color Shades and Composition

The color of gold bronze pigments is determined by the copper-to-zinc ratio in the alloy:

• Rich Gold: Higher copper content, typically around 90% copper, 10% zinc, offering a deep, warm gold shade.

• Rich Pale Gold: A slightly lower copper content, resulting in a lighter, more brilliant gold.

• Pale Gold: Lower copper content, yielding a greenish-gold or "pale gold" shade.

• Copper: Very high copper content, providing a reddish, copper-like tone.

Production Process

Gold bronze pigments are produced through a series of steps, including alloy melting, atomization, and attrition (grinding) to produce flake-like particles. The flakes are then classified by size and may be coated or treated to improve performance characteristics. Encapsulation technologies, such as silica coating, are used to improve thermal and chemical resistance.

Key Properties and Applications

Key Suppliers

Metapol is a leading manufacturer of copper-zinc alloy pigments, offering a wide range of products based on aluminum and copper-zinc alloys. Their English Green U 2530 and Ducat U 2530 products are examples of copper-zinc alloy pigments used in decorative coatings, textile coatings, and screen printing applications. Sun Chemical (DIC) offers the Benda-Lutz® Goldbronze and Copper series, providing improved temperature stability for water-based coatings.

Future Outlook

Copper-zinc alloy pigments are expected to see continued demand, driven by the growing preference for metallic effects in packaging, automotive, and consumer goods. The development of more stable and environmentally friendly formulations will further enhance the appeal of these versatile pigments.

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