Protecting NdFeB Materials: Exploring Innovative Coating Technologies

In the previous newsletter, we introduced how GBD methods can further enhance the performance of sintered NdFeB magnets, maintaining excellent magnetic properties while reducing costs. After obtaining NdFeB magnets in the desired finished sizes, we also need to customize surface coatings to meet various requirements such as corrosion resistance and different surface gloss levels, depending on the magnetic application environment. In this issue, we will present several surface coating technologies that effectively isolate the magnets from external corrosive environments, protect the NdFeB material, and provide the magnets with different metallic lusters for enhanced aesthetics.

The main surface coating technologies include: electroplating, chemical plating, conversion coatings (phosphating), and organic coatings.

Electroplating: Electroplating uses external current to reduce metal cations in the plating solution, forming a metal layer. Common electroplated metals include nickel, zinc, and copper. Electroplating is currently the most widely used protective technology, offering excellent corrosion resistance, good adhesion, and cost efficiency.

Chemical Plating: Chemical plating generates a film layer through redox reactions in the plating solution without requiring an external current, suitable for complex parts. Although less commonly used, chemical plating can provide effective protection in certain cases.

Conversion Coating (Phosphating): Phosphating involves the reaction between the metal substrate and a corrosive environment to generate an adherent film that blocks direct contact between the environment and the substrate, providing protection. Phosphating offers cost-effectiveness and temporary protection.

Organic Coatings: Organic coatings use substances like epoxy resins and phenolic resins to form a protective film. The main application methods include electrophoretic deposition and spray coating. Electrophoretic deposition moves charged resin particles in an electric field to form a coating, while spray coating uses a high-pressure spray gun to apply resin solutions to the magnet surface. Both methods provide high corrosion resistance and excellent surface gloss.

As environmental concerns become more prominent, many NdFeB enterprises face challenges in managing pollution and struggle to perform electroplating processes independently. Since 2015, the INNUOVO Surface Treatment Center has been operational with multiple automated processing lines capable of completing electroplating, phosphating, electrophoretic epoxy, and spray epoxy processes independently. The electroplating production lines at INNUOVO include zinc and nickel plating, offering various coating options such as blue-white zinc, color zinc, and nickel-copper-nickel composite coatings to meet different corrosion resistance and aesthetic requirements. Electrophoretic and spray epoxy technologies offer high corrosion resistance and excellent gloss, while phosphating coatings provide cost-effective solutions.

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