NdFeB magnet and hard Ferrite are the two types of permanent magnets mainly used on the pipeline pigs.
Neodymium magnets have higher remanence, much higher coercivity and energy product. The use of NdFeB magnets therefore not only increases the magnetic force, but also makes the product more compact.
But they are sensitive to oxidation due to its high iron and surface treatment (Ni, Zn, Epoxy) is essential. They also have lower Curie temperatures than other types of magnets. Now special neodymium magnet alloys, including terbium and dysprosium, have been developed. They have higher Curie temperatures and allow them to withstand higher working temperatures.
Therefore, NdFeB magnets are available in different temperature ratings (from 80-220℃). You need to choose between ambient and high temperature magnets depending on your specific application. Our current range of magnet materials for pipe inspection MFL and pipeline cleaning pigs includes grades N35 and N42 (80°C), N52 (60°C), N50M and N52M (100°C), N40H and N48H (120°C).
Hard Ferrite magnets are the least expensive class of permanent magnet materials. They are extremely corrosion resistant. Even when used in water, they are completely non-corrosive.
Although not as powerful as neodymium magnets – typically offering around 1/7th the pull force of similarly sized NdFeB, their high coercivity and relative low cost make them ideal for use in high temperature application. They can be used up to +250 degrees C (482F) and sometimes up to +300 degrees C (572F) in special circumstances.