Introduction To Corrosion Resistance Of Different Magnetic Materials

Permanent magnet materials contain iron elements, iron shows the most significant ferromagnetic properties of all elements, which is why it exists in the most powerful magnets. However, iron is highly reactive to water, making magnets with a high iron content very susceptible to corrosion.

Other ferromagnetic elements used in different types of permanent magnets include nickel, cobalt, gadolinium, and dysprosium, all of which have an effect on magnetic strength and corrosion resistance.

There are many factors to consider when exploring custom magnetic components, and corrosion resistance is one of the key factors you just considered, so take a look at our breakdown of the corrosion resistance of each magnetic material.

1. NdFeb magnet

Currently, the strongest commercial permanent magnet on the market is Ndfeb magnets, but due to their high iron content (64-68%), they are also highly corrosive in wet environments.

Modern manufacturing techniques have found that small amounts of other rare earth elements, such as dysprosium, are added to NdFeb alloys to improve corrosion resistance and other magnetism.

Neodymium magnets are almost always coated before use because of their susceptibility to corrosion.

A very common coating for Ndfeb permanent magnets is the nickel-Copper-nickel triple, however, there are many other suitable options including but not limited to gold, silver, zinc, tin, epoxy resins, PTFE, and a variety of paints and varnishes.

2. SMCO magnet

SMCO magnets, like NdFeB magnets, belong to the rare earth family and are more resistant to corrosion even when uncoated. This is because most of the iron used in neodymium magnets is replaced by cobalt, which does not react with water.

You may find some SMCO magnets coated, mainly for aesthetic purposes or for application-specific reasons, such as adhesion or sterility.

SMCO magnets are widely used in Marine and offshore applications when having to cope with constant exposure to brackish air.

3. Alnico magnet

Both Alnico magnets and ferrite magnets are known for their corrosion resistance, although they do not have the same magnetic level as rare-earth SMCO magnets and NdFeB magnets.

Some grades of Alnico magnets do contain trace amounts of iron, so some slight surface corrosion will occur over time if exposed to water. However, nickel-cobalt alloys perform very well when exposed to other lubricants, such as oils, solvents or alcohol.

Traditionally, Alnico magnets are painted in red; It is not clear how or why the custom began, but it is still used today, and most of the Alnico magnets are instantly recognizable by their signature red finish.

4 Ferrite magnet

Ferrite magnets, also known as ceramic magnets, are made of iron oxide, so they do not corrode even when submerged in water.

Because of their unparalleled corrosion resistance, ferrite magnets are rarely coated, but because ferrite is a dusty material, some applications require some surface treatment to avoid dust diffusion.