Sintered NdFeB permanent magnet material is a highly active powder metallurgy material, which is prone to corrosion. Therefore, when it is surface treated, appropriate pretreatment and electroplating processes should be carefully selected.

Prior to electroplating of sintered NdFeB permanent magnet materials, chamfering, degreasing, pickling, ultrasonic cleaning, and other processes capable of stabilizing the clean surface are required to obtain a coating having good bonding, low porosity, and long lasting corrosion resistance.

When selecting the electroplating process, it is necessary to consider the protection of the process and the practicability of the production. It must also pay attention to the environmental impact and damage caused by the electroplating emissions. The environmental conditions for the use of each plating layer are shown in the table.

Plating category

Post processing code

Instructions for using environmental conditions

Ni

-

Exposure to indoor atmospheres where condensation may occur, and requires long-term stability and long service life to ensure appearance and intrinsic properties.

Zn

C1A

Used in mild corrosion conditions, limited corrosion resistance for short-term pollution discoloration.

C2A

Used in harsh environments such as organic corrosive atmospheres

CuNi

-

Exposure to indoor atmospheres where condensation may occur, and requires long-term stability and long service life to ensure appearance and intrinsic properties.

NiSn

-

Good appearance and solderability for applications where the surface is solderable and electrically accessible.

NiAg

-

Good appearance and solderability, low contact resistance, poor surface resistance to discoloration, used for surface solderable and electrical contact.

NiAu

-

Good decorative, non-discoloring surface, low contact resistance, high cost, high-reliability electronic equipment for electrical contact, and high-end decorations.

    Chamfer

Small parts chamfering can be done with a centrifugal finishing machine. Larger parts can be ground with a grinder and then chamfered with a spiral or centrifugal vortex finisher. Chamfering should be carried out in neutral or weakly alkaline media. Never use chamfers with acidic or corrosive media.

Degreasing

        It should be carried out in neutral and weakly alkaline degreasers. In order to avoid oxidation or hydrogen permeation, it is best not to perform anode or cathodic electrolysis.

Pickling

       Use a dilute nitric acid solution or a weak organic acid for pickling in a short time, but should not be pickled in a strong halogen acid. Avoid pickling in a high concentration of strong acid. Otherwise, the surface of the material will be sharply roughened or even powdered.

     Ultrasonic cleaning

       Ultrasonic cleaning should be carried out after each treatment process to ensure the cleaning effect and prevent contamination of the next process.

      plating

       It is advisable to use a low-corrosion plating solution for electroplating. It is best to use a multi-layer composite coating to meet the actual application requirements. It can be post-treated as necessary to further improve corrosion resistance.