NdFeB magnets are mostly small workpieces (mass 0.25 ~ 20g), electroplating production is mainly based on barrel plating, supplemented by hanging plating. However, the barrel plating of NdFeB parts is much more difficult than ordinary steel parts.
1) The bismuth chemical activity in the material is extremely strong, and the NdFeB parts will generate hydrogen gas and even corrode when in contact with water, so:
a. The acid and alkali should not be too strong when pre-plating treatment, otherwise the material matrix is susceptible to corrosion, and hydrochloric acid should be avoided due to the reaction between chlorine and hydrazine in hydrochloric acid;
b. Selecting a simple salt plating solution (such as watt nickel and potassium chloride galvanizing) during pre-plating or direct plating, it is easy to oxidize the parts and affect the bonding force between the plating layer and the substrate, and the plating solution is contaminated due to corrosion of the parts;
c. It is difficult to select a large volume of the drum (causing to affect the production capacity), otherwise, the impact on the mixing cycle is large and the parts are seriously oxidized.
2) Neodymium iron boron magnets are magnetic functional materials, and metal plating will affect their magnetic properties. Therefore, how to coordinate the type, combination, and thickness of the coatings (these are related to the corrosion resistance of the coating) and the magnetic properties of the products, It is one of the difficulties in the electroplating of NdFeB.
3) The surface of NdFeB magnets is loose and porous, rough and uneven, and the microscopic surface area is much larger than the macroscopic surface area, so:
a. The surface dirt is not easy to clean, and the pre-plating treatment requirements are high;
b. It is impossible to select a complex plating solution with good bonding strength and good corrosion resistance during pre-plating or direct plating (because of the low current efficiency of the complex plating solution, it is difficult to deposit on the surface of porous parts), such as alkaline copper plating and Alkaline galvanizing, etc.
4) NdFeB material is brittle and the surface is easily damaged, resulting in:
a. Workers are more difficult to operate;
b. It is difficult to select a large-volume roller (otherwise, the part flips strongly, causing bumps), which affects the improvement of labor productivity.