Anodes are steel core rods surrounded with either magnesium, aluminium or zinc and are installed on the top of hot water tanks during production to prevent rust and corrosion. They’ve been a staple feature for decades and go a long way in avoiding heater damage and hefty replacement costs.
The term “sacrificial anode” is derived from the anode’s function; the rod will corrode in place of the heater’s exposed steel through a process called electrolysis, which is utilised whenever metal needs protection from water. This occurs when the two pieces of submerged metal react to a voltage.
During electrolysis, the less noble (more reactive) metals will corrode before the more noble (less reactive) metals. In the case of anodes and water heaters, magnesium, aluminium and zinc are less noble than steel, so they will corrode first, acting as a kind of shield for heater. Magnesium anodes are the most common and are used in manufacturer tanks. Aluminium anodes are generally used in hard water areas thanks to their higher hard water resistance; ideal for old tanks.
Depending on the quality of the anode and the volume of water involved, a typical rod will last 3½ to 5 years. Once fully corroded, the anode will cease to protect the heater, which will begin to deteriorate if not addressed. In time, a rusting heater will cause problems and require replacement more costly than a new anode. Regular anode replacement is strongly recommended, so get in touch with Anode Suppliers for a reliable anode supply.