Magnet Coating & Plating Options – Surface Treatment for Neodymium Magnets

Magnet coating is very important protection for neodymium magnet. Surface treatment is a process applied to the surface of a material to make it better in some way, for example by making it more resistant to corrosion or wear.

Corrosion can cause unprotected magnets to spall off a surface layer, or to crumble into a powder. Use of protective surface treatments such as gold, nickel, zinc, and tin plating and epoxy resin coating can provide corrosion protection.

Coating makes brittle permanent magnet more durable; multilayered metal plating like NiCuNi will improve the magnets resistance to chipping and wear, particularly around corners.

Harsh environments like salt and humidity in regions near the ocean can’t be ignored while choosing a coating.

permanent magnet coating

The most common type of plating Nickel (Ni-Cu-Ni) is mainly for conventional environment and has proven to be very resilient when subjected to normal wear and tear. However it will be corroded in prolonged exposure to salt water, salty air, or harsh chemicals.

Everlube is a new coating appearing in recent years which will provide excellent resistance to heat and viscous properties and can be used on auto parts.

If coating can’t help, low weight loss magnet (hast magnet) is also a good solution.

Do all permanent magnets need to be plated?

No. Only rare earth magnet which is extremely brittle and also vulnerable to corrosion, is usually plated or coated to protect it from breaking, chipping, or crumbling into powder.

There are two types of rare earth magnets: neodymium magnet and samarium–cobalt magnet. The former is more vulnerable to oxidation than the latter.

Basically, there are five kinds of surface treatment that can be applied to permanent magnets.

Electrolytic plating

To make cathode electrophoresis by chemical principle, it is a common surface treatment process in the world currently.

a. salt spray test for 48 hours
b. constant temperature and humidity for 240 hours
c. good oil resistance and solvent resistance.
d. smooth surface, beautiful appearance

Anti-rust oil

To coat with a layer of anti-rust oil film evenly on the surface of product by the impregnation method. It can improve anti-rust capability without change of the appearance and size of product. It is particularly suitable for small-bore product

a. efficiency
b. simple process


To spray anti-corrosion coating evenly on the surface of product by spray principle. It’s especially used on small product with the weight less than 1 gram, or the outer diameter less than 5mm.

a. salt spray test for 24 hours
b. constant temperature and humidity for 240 hours
c. efficiency & high pass rate
d. good consistency


The most corrosion resistant, thicker than other plating, mold required to create the plastic shell.

Special treatment

To permeate special glue into the gaps of product by negative pressure method. It is suitable for products which work in the oil or solvent environment.

a. seal porous surfaces
b. increase product strength
c. work long time in the oil or solvent environment

Coating TypeThicknesColorPCTSalt Spray TestAdvantage
NiCuNi10-20μmBright Silver> 48-72 H> 24-72 Hexcellent humidity
heat & salt spray resistance
Epoxy10-30μmBlack or Grey> 72-108 Hexcellent humidity & adhesion
heat & salt spray resistance
Coloured Zn4-8μmShining colour> 48-72 Hexcellent salt spray resistance
Zn4-8μmBright blue> 24-48 Hregular protection
applied to most products
Everlube8-20μmYellow> 72 H> 96 Hexcellent salt spray resistance and adhesion
Black Nickel10-20μmBright Black> 72 H> 48-96 Hexcellent humidity
heat & salt spray resistance
Passivation / Phosphorization≤ 1μmDark grey≤ 2.5 H
emerge in 3% NaCl liquor
temporary protection
Sn10-25μmSilver> 48 H> 36-72 Hexcellent humidity
heat & salt spray resistance
Au10-15μmGolden> 48 H> 12 Hgood looking
Ag10-15μmSilver> 48 H> 12 Hgood looking
Chemical Nickel10-30μmBright Silver> 72 H> 96 Hexcellent humidity
heat & salt spray resistance
Organic Aluminium6-20μmdarkish silver> 48 H> 288 Hexcellent humidity
heat & salt spray resistance
 Vacuum Aluminum10-30μmBright Silver> 48 H> 288 Hexcellent humidity
heat & salt spray resistance


1. The time for salt spray test in the table is obtained after some special process. We make magnet coating by conventional process unless otherwise specified.
2. The SST result will be different due to different electroplating process. SST result of barrel plating (small size) product is better than rack plating (large size) product.
3. Salt Spray Test (SST) test condition: 5% NaCl, 35℃, continuously spray after a certain time, check the corrosion on the product surface.
4. Pressure Cooking Test (PCT) test condition: 2 atm, 95% RH(relative humidity), 121℃, then test the coating adhesion. The products with coating Zn, passivation/phosphorization, or epoxy are not suitable for PCT.
5. The methods for coating quality test: drop test, cross cut test, heating and chilling test, constant temperature and humidity test etc.