The surfaces of electrical contacts are usually contaminated by foreign layers. Such layers may consist of dust or grease, or of films produced by adsorption, tarnishing or corrosion. The applied voltage is regarded as “low” when it is too small to initiate conduction by any process analogous to breakdown. The problem in such circumstances is to obtain a metal-to-metal contact mechanically. An attempt is made, for the first time, to describe the behaviour of a closed contact subjected to corrosion, and the closure processes for a corroded contact, both with and without “wipe.” The principles outlined provide some theoretical basis for design and testing techniques. Attention is also given to sliding contacts and, in particular, to the exposed intermittently-operating type: some new approaches to the problems involved are suggested, perhaps the most important being the development of a new technique for the continuous dry lubrication of sliding contacts in mechanical and electrical systems.