Anode rods in water heaters can be made using different materials. The rods rely on a chemical process called electrolysis, which leads to the deterioration of the anode rod instead of the metallic material used to make the tank. Essentially, the rods are made of sacrificial metals that draw corrosion towards them at the expense of the other material around. Once the sacrificial metal has been fully depleted, then the corrosion effects extend straight to the material used to make your heater. Here are the various kinds of anode rods used in domestic water heaters:
Impressed Current Rods
Impressed current rods are an inert type of anodes used in cathodic protection systems for metals. The rods depend on a direct current from an outside source referred to as a rectifier. The current enables the rod to develop a significant potential difference between the rod itself and the surface that you want to protect. They do not have a self-generated current that ordinary anode rods can generate when put in a corrosive environment.
One of the top benefits of impressed current rods is that you don't need to replace them after some months or years of use. The rods are made using inert materials that are resistant to corrosion and depletion. These materials include cast iron, silicon iron, graphite, and titanium alloys among others. In spite of their inertness, you need to clean the anode rods from time to time to sustain the electrical charge between them and the material you are protecting.
Aluminium anodes can be referred to as the traditional anodes because of their popularity. They have been used to protect water heaters for many years. Aluminium is very reactive when compared to other metals like copper. This makes them ideal for protecting heaters often used to warm hard water. To add on that, aluminium anodes can be designed in many configurations to accommodate various usage needs.
Magnesium is another popular anode used to protect water heaters. It is preferred in many domestic applications because magnesium has no poisonous effects, meaning that the water is safe for drinking. The sad part is that magnesium is less aggressive than aluminium. When used in hard water, you must keep a keen eye on the lining of the heater for corrosion. If you continue using magnesium in a corroded water tank, the resultant electro-chemical reaction produces hydrogen. This causes leakages in the heater.