Magnetic fluids in sealing and lubrication – a state of the art review

The paper is a review of the properties and functions of magnetic fluids and their potential use in tribological applications, such as seals and bearings. They offer new possibilities for achieving low friction, low wear, and no leak- age. Magnetic fluids or ferrofluids consist of magnetic particles suspended in a carrier fluid and a coating on the particles. The coating prevents the agglomeration of the particles through magnetic and molecular attraction by keeping the distance between them sufficiently large. The magnetic fluids have the basic properties of liquids and they act like ferromagnetic materials in the presence of an external magnetic field. Shaft sealing is the most promising potential application for ferrofluids. Magnetic seals have zero-leakage and low friction, they are non-stick and they have high-performance properties. Lubrication is another important application of ferrofluids. The advantage over conventional lubricants is the possibility of keeping the lubricant exactly and only where it is needed. They provide the possibility of increasing the life of components. Furthermore, because they do not contaminate, ferrofluids are also used as lubricants in clean environments.