Abstract: Cathodic protection of a deep well submersible pumping assembly against the corrosive effect of electrolysis is achieved by providing a DC voltage source at the downhole pumping assembly, the negative terminal of the source being electrically connected to the metal surfaces which are in contact with the well fluid while the source's positive terminal is electrically connected to a sacrificial anode submerged in the well fluid. Current flows from the anode to the metal surfaces to reverse the process of electron flow caused by the electrolytic corrosion, thereby inhibiting the corrosion process on the metal surfaces. In effect, the corrosion is transferred to the sacrificial anode.