Abstract: Protection from corrosive effects of water in hot water tanks is provided by an electrochemically active noble metal type anode disposed in the hot water tank and supplied by a selected level of current passing from the anode through the water to the tank. The anode is configured in such manner as to cause the current to be distributed throughout the entire tank and thus for a conventional tank takes the form of a long thin anode. The noble metal is shown to be clad or plated onto an electrically conductive and, under anodic conditions, chemically inert strip of metal supported on a suitable electrically insulative member. The power supply provides a minimum protective current for water having low corrosivity characteristics, a maximum protective current for water having high corrosivity characteristics and intermediate these two extremites a level which varies with the degree of corrosivity of the water.