A sealing device for a bearing unit, having a stationary part, which is in turn provided with a first metal screen, an elastomer coating co-moulded on to the first screen, and a radially inner contact lip belonging to the elastomer coating, and a rotatable part provided with a second metal screen with which the contact lip makes a sliding contact, the sealing device being provided with at least one appendage which faces a radially inner flanged ring of the bearing unit and interacts with this flanged ring to form a barrier against the entry of contaminants.