In the presence of dissimilar metals whereby one becomes an anode and the other a cathode if nothing is done to prevent it the anodic material will go into solution (corrode) and protect the cathodic material. At the surfaces where the ions flow into the metal from the electrolyte no corrosion occurs. At the surfaces where the ions flow from the metal into the electrolyte (water) the metals corrode. What is corrosion?Ĭorrosion is defined as a flow of electric current caused by a potential difference between two metals. So-called sacrificial anodes are used to protect systems that include large quantities of stored water. They are made from metals that are low on the noble scale, such as magnesium or aluminium, which corrode more easily. So anodes are placed within these systems to, effectively, attract the corrosion away from other components. This is potentially damaging to the surface metals within a water heater, boiler or storage tank and these components are expensive and often complicated to replace. Water is highly solvent and corrosive and there are few materials that will not succumb to its effect, given time.

Made of Magnesium, these anodes protect the expensive metal components in the water heater by corroding at faster rate.

Sacrificial rod water heater