Cathodic Protection

When a metal surface requires protection from corrosion, a common technique to achieve that goal is to actually make the metal surface a cathode of an electrochemical cell. This cathodic protection system is often used as a way to protect an assortment of surfaces that are susceptible to the problems presented by corrosion, like storage tanks or pipelines.

While cathodic protection, when accurately performed, can be an effective strategy for combating the cracking that can occur from stress corrosion, there is always the chance that the surface may be subjected to the production of molecular hydrogen. If this happens the metal surface is subject to embrittlement, a bane for ships, oil well casings, and pier piles. As you can imagine, corrosion in these areas is difficult to correct and repairs are very costly.

Looking back into the history of the cathodic protection theory, we discover that a very bright fellow named Sir Humphrey Davy was concerned with the effects of corrosion on the ships of the Royal Navy. He experimented with copper and iron anodes to overcome the detrimental abilities of seawater. His cathodic protection testing was successful and he opened up a whole new science based on his proven cathodic protection system theory.

Since those early days of Sir Humphrey's experiments, we have seen many applications for cathodic protection.

Nowadays not only are cathodic protection systems instrumental in guarding against corrosion in marine environments, this method is being used to protect steel from corrosion that is chlorine induced.

How is a cathodic protection system installed? This is dependent upon the type of cathodic protection shielding that's being used. There are two kinds: the sacrificial, or galvanized system, and the impressed system. Here's a brief overview of each.

In a sacrificial system the cathodic protection equipment will be galvanic diodes, often made from zinc or aluminum. This system requires no power supply to activate or maintain the cathodic corrosion protectors.

However, the impressed system does require a direct current power supply to perform cathodic protection services and this is provided by a cathodic protection rectifier. When considering the two systems, the cathodic protection rectifier's expense should be factored in to arrive at the overall cost. Since competition tends to lower prices, it's good to know that over a hundred firms manufacture cathodic protection supplies and over fifty companies distribute them.

If you are concerned with corrosion on metal surfaces, especially surfaces exposed to marine environments, it is important to be aware of cathodic protection.