One method used to prevent rust, is to insulate the metal from moisture and oxygen by covering it with protective chemical layers or paint. This method is effective as long as the protective surface is not damaged, for example, stone chips, scratches, abrasions in the joints. In real terms this is not possible and where damage occurs, no matter how small, rust will occur. It is also impossible to cover every area on the vehicle with this method and hard to reach places are left unprotected, often these are the areas that are most prone to corrosion. Another method is Capacitive Coupling, used by some products, which relies on the paint as a dielectric or barrier