Coolant manufacturers continue to increase coolant life and improve coolant performance. Disposal of used machining coolant has become its own concern. When machining heavy metal alloys with lead, chromium, nickel or other toxic heavy metals as an ingredient, the coolant may be considered hazardous waste depending on local EPA regulations. That is why the less material there is to dispose of, the better. And one way to reduce disposal of machining coolant is to clean and recycle it.
Recycling means that the coolant has to be cleaned and reused.
Cleaning includes removing any ferrous materials that get into the coolant. Materials that have a very high magnetic susceptibility and are strongly induced by a magnetic field, such as iron, are termed ferromagnetic. Iron, nickel and cobalt are all ferromagnetic elements. Materials that have a low magnetic susceptibility and a weak response to a magnetic field are termed paramagnetic. Many ferrous alloys like stainless steel or several varieties of iron-bearing minerals are classified paramagnetic.