In the selection of NdFeB Strong Magnet coatings, galvanized nickel plating is recommended on all magnets that require salt spray test for 72 hours. As neodymium magnets reacts easily to oxygen thus oxidizes quickly if untreated, galvanized nickel plating provides surface protection which maintains stability in most moist and temperature sensitive environments.
Nickel plating on magnet that require salt spray test for 72 hours is difficult due to porosity. Salt water can create defects that are prevalent in thin nickel deposits which seriously reduce the value of the protective coating. As requirements are different among customers in regards to salt, acid and alkali resistance, applying just nickel plating may not work.
Alternative option 1:
Apply Parylene coating. Parylene is a p-xylene polymer which provides fully protective coating through vacuum deposition to create uniform thickness while extremely resistant to chemical corrosion. As it has very low moisture/gas permeability, it can help achieve resistance to organic solvents.
Alternative option 2 – Electro-galvanization for salt spray test between 12 hours to 48 hours:
If you require magnets with coating to withstand salt spray test for 12 hours, you could also go with the option of electro-galvanized zinc. There are different options provided in regards to color of coatings such as white, blue-white, color, and black.The current market salt spray test is as followed:
|
White zinc |
Blue-White zinc |
Color zinc |
Black zinc |
|
16 hours |
24 hours |
48 hours |
12 hours |