In this blog, we take a look at how Sacrificial Anodes functions. Read on to find out more...
When a metal structure is submerged or buried oxidization can cause rust, a chemical reaction of a metal against its surroundings. This reaction results in metal loss and, ultimately, a loss of overall structural integrity over time, until the point of failure if unaddressed.
A sacrificial anode (or galvanic anode) is the main component of a galvanic cathodic protection system. These blocks, rods, plates or extruded ribbons are made from metal alloys that are less active in voltage than the structural alloy it needs to protect. In other words, the supply of electrons that encourage the dissolution of the primary metal will be diverted or consumed by the “sacrificial” metal instead.
These types of systems are used to protect metal structures (most-often steel) from the harmful effects of rust by using the physics principle of anodes.
Three main metals remain popular for producing galvanic anodes, these are magnesium, aluminium and zinc. Each has a unique application that is advantageous to its unique potentials.
Magnesium: Of the three metal alloys, Magnesium sacrificial anodes have the most negative electrode potential. You’ll find that it’s suited for areas where the electrolyte resistivity is higher. For example, it can be used for protecting on-shore pipelines and other buried structures. In Australia, Magnesium is also used to construct hot water anodes for the protection of heating systems, as well as anodes for safeguarding vessels in freshwater environments.
Zinc: This is considered a reliable material too but it is not suitable for use at higher temperatures. Similar to aluminium, zinc is generally used in salt water, where the resistivity is generally lower. For example, zinc-based anodes protect the hulls of ships and boats, offshore pipelines and production platforms, salt-water-cooled marine engines, small boat propellers and rudders, as well as storage tanks.
Aluminium: These types of anodes have several advantages, such as a lighter weight, and much higher capacity than zinc. However, their electrochemical behaviour is not considered as reliable as zinc in certain applications.
As discussed, sacrificial anodes are used to protect the hulls of ships, water heaters, pipelines, distribution systems, above-ground tanks, underground tanks, and refineries – to name a few. The application will depend largely on the chemical and mineral environment (whether soil or water). Remember, the anodes in this type of cathodic protection system must be periodically inspected and replaced when they are consumed to the point of depletion.
Our team of consultants and installers in Australia are available to assist with all necessary FAQs you’ll need to know about in order to maintain and replace your sacrificial anodes.
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