II. Basic Knowledge of NdFeB Electroplating (Part 2)

1. Pre-treatment Process
Deburring → Water rinse → Electrolytic degreasing → Water rinse → Ultrasonic degreasing → Water rinse → Acid pickling → Water rinse → Ultrasonic water rinse → Activation → Water rinse → Ultrasonic water rinse → Electroplating.

2. Chemical Immersion Plating
Due to the high chemical activity of NdFeB material, parts should be plated as soon as possible after activation. Otherwise, surface oxidation can easily occur, leading to poor adhesion between the coating and the substrate. Chemical immersion plating offers a much higher deposition rate than electroplating, effectively slowing down the oxidation process on the part surface during plating and thereby ensuring strong coating adhesion. For NdFeB, chemical immersion zinc or chemical immersion nickel processes can be selected.

3. Barrel Zinc Plating
The high chemical activity of NdFeB means that a zinc coating provides limited anodic protection to the substrate. Therefore, a high-density coating is required. However, the commonly used potassium chloride zinc plating process (or sulfate zinc plating + potassium chloride zinc plating) typically produces coatings with somewhat inferior density. These coatings also contain significant amounts of surfactants, resulting in lower quality of both the coating and the subsequent passivation film. Consequently, zinc plating for NdFeB is mostly used for lower-grade products or those intended for less demanding environments.

4. Barrel Nickel Plating
Barrel nickel plating for NdFeB typically employs a combined process of nickel-copper-nickel plating. This combination offers good coating adhesion, corrosion resistance, and decorative appearance, while having a moderate impact on the magnetic properties of the magnet.

• Pre-plating Nickel (Base Layer): This serves a dual purpose: to enhance coating adhesion and to provide a base for the subsequent copper layer. The barrel dull nickel process is commonly used for this stage.

• Copper Plating (Thickening Layer): This step increases the corrosion resistance of the composite coating and reduces its impact on the magnet’s magnetic properties. The barrel pyrophosphate copper process is often employed here.

• Top Layer: A final layer of bright nickel is applied.

5. Electroless Nickel Plating (for Enhanced Performance)
If further improvement in corrosion resistance is required, an electroless nickel plating process can be chosen. Electroless nickel coatings exhibit low porosity and excellent corrosion resistance. Furthermore, by controlling the phosphorus content in the coating, the impact on the magnetic properties of the magnet can be minimized.