Color Zinc

Color Zinc Coating Magnets

Electroplating of sintered Neodymium magnet include zinc plating, nickel plating, tin plating, and other precious metal plating, where only zinc plating and nickel plating can be directly deposited on the magnet surface, thereby, zinc plating and Ni-Cu-Ni plating has always been the mainstream surface treatment technology for sintered Neodymium magnet. The standard electrode potential of zinc is -0.76V, then zinc plating layer is generally acted as the sacrificial anode to steel workpiece. However, NdFeB alloy exhibits relatively higher chemical activity and zinc plating layer unable to embody anodic protection, therefore, protection of Neodymium magnet is primarily relying on the dense passivation film on zinc plating. Zinc plated Neodymium magnet can be divided into blue-white BW zinc plated Neodymium magnet and color zinc plated Neodymium magnet according to the passivation effect. Corrosion resistance of color zinc plated Neodymium magnet is slightly better BW zinc plated Neodymium magnet.

Color Zinc Plated Magnets Feature
Material: Color Zinc
Coating thickness: 4-15um
Advantage: Excellent salt spray resistance
Application: High requirement of humidity & salt spray resistance, such as Automobile roof motor.

Color Zinc Coating Magnets

To understand the nature and application of color zinc coated magnets, one must first consider the inherent properties of neodymium (NdFeB) magnets. Sintered neodymium magnets are composed of neodymium, iron, and boron, making them highly susceptible to oxidation and corrosion. Because these magnets are chemically active, they require protective surface treatments to ensure longevity.

The process of applying a color zinc coating involves electroplating a layer of zinc onto the magnet, followed by a specific passivation treatment. While standard zinc plating (often blue-white) provides a basic sacrificial anode layer, color zinc plating utilizes a specific passivation effect that results in a thicker, more durable conversion film, offering superior salt spray and corrosion resistance compared to standard blue-white zinc coatings.

The logical steps in the production and utility of these magnets include:

Material Preparation: The sintered NdFeB magnet is cleaned and prepared for electroplating.
Electroplating: A layer of zinc is deposited onto the magnet surface. Zinc is chosen for its cost-effectiveness and its ability to act as a sacrificial anode.
Passivation: This is the critical step that differentiates color zinc from other zinc finishes. The magnet is treated with a passivator (historically hexavalent chromium, now increasingly trivalent chromium) to create a dense, protective film.
Application: Due to their enhanced resistance to humidity and salt spray, color zinc coated magnets are frequently employed in demanding environments, such as automotive roof motors, wind turbine generators, and other industrial motor assemblies where environmental exposure is a concern.

While nickel plating is often preferred for its aesthetic brightness and superior corrosion resistance, color zinc remains a preferred choice when a balance between cost-efficiency and moderate-to-high environmental protection is required.