Know Your Anodes: How CP Systems Stave Off Corrosion
When you really think about it, the progress that has been made in the construction industry is incredible. After thousands of years, we're still finding ways to improve our methods, protect our structures and save our resources, and that innovation is truly impressive. While cathodic protection systems are not necessarily a new technology, the way they work still sounds like something out of a sci-fi movie. It's really fascinating—but it also allows you to understand which metals are best for various types of structures.
Drawing Corrosion Away
When metal buildings or structures are placed underwater or underground, they are immediately susceptible to rust and corrosion in ways that ordinary buildings above the surface are not. Unfortunately, that also means they're extremely difficult to repair or protect; it can be prohibitively expensive to pull the metal up to be worked on, if not completely impossible. As such, CP systems were developed to help prevent corrosion from occurring in the first place. Essentially, what they do is present a more attractive target for the corrosion to work on, discouraging it from attacking the construction itself.
Electrons and Electrolytes
The CP system puts an electric current through the main construction material and the anode. This interrupts the natural process of corrosion by forcing the electrons to flow to the anode instead of the construction. While the construction will still experience reduction, it will not oxidise; this is the problematic part of corrosion and what damages the integrity of the material. Instead, it is the anode which will oxidise and eventually need to be replaced.
There are several different materials used to create anodes. You'll need to determine which has the properties that best suit your construction—or rather, which best suits the environment in which your construction is placed. Zinc and aluminium anodes are best suited to saltwater environments, whereas magnesium is more suitable for freshwater. This may be harder to determine for underground constructions, but experts will be able to advise you. The temperature of the area will also need to be taken into account; magnesium and aluminium both perform better in extreme heat than zinc does. It's vital that you consult experts to ensure you're using the correct anode type, as each metal will be rendered completely ineffective in the wrong conditions.
No solution is foolproof, and of course, the CP system will need to be maintained in order to continue being effective. It can also be extremely complicated to get right—but once it works, it at least allows for underwater and underground structures to be infinitely more viable and affordable.