cathodic protection

What is cathodic protection?

Corrpro has been a leader in the corrosion industry for over 35 years. With almost 200 NACE-certified personnel and dozens of professional engineers, Corrpro is a leading provider of cathodic protection services. Our team understands corrosion and can help you protect your assets.

To understand cathodic protection is and how it works, we must first understand the basic principles of corrosion. The metals we use on a daily basis do not naturally appear in the form in which they are used. Instead, most metals are first mined as ores, then refined and often combined with other compounds.  

To extract pure metal from ore, the raw product is subjected to extreme heat to remove impurities. This results in a refined product that has added energy to the metal. Nature won’t let this added energy stay in the metal forever. With exposure to electrolytes such as soil, water or concrete, any products made from ore will eventually revert back to their natural state. One example is steel, which reverts back to iron oxides – or rust.

How does Cathodic Protection work?

Cathodic protection can help us maintain the added energy in refined metals, thus preventing the onset of corrosion. Each different type of metal has its own unique “potential” ranking in the Galvanic Series of Metals. Metals with more negative "r" potentials corrode first, as the release of energy coincides with the degradation of the metal into its natural state.

Thus, metals with higher negative potentials, including magnesium, zinc and aluminum, corrode easily upon exposure to the elements as they gradually lose energy. Metals with lower energies include silver, gold and platinum. Because the energy levels in their refined states are lower, these metals do not corrode as readily.

A cathodic protection system uses this basic energy principle to prevent corrosion. By attaching a lower energy metal (cathode) to a higher energy metal (anode), we can prevent degradation of the “cathodic” metal. For instance, to prevent the corrosion of a steel pipe, you could connect it to a higher energy metal such as magnesium. The transfer of energy causes the magnesium anode to corrode first while preserving the steel pipe.

An electrical connection between the anode and cathode can be achieved using a wire, metal coupling, welding or direct physical contact. In large cathodic protection systems where a galvanic anode may not provide adequate protection, this connection is regulated using a transformer-rectifier. A rectifier converts AC power to a DC output, ensuring that there is enough current to provide complete corrosion protection to large assets.

Different Applications for Cathodic Protection

Water and energy pipelines are not the only assets that can benefit from cathodic protection. Cathodic protection systems are used for a variety of different materials and applications.  Fuel tanks, water tanks, offshore structures, marine vessels and concrete structures with metal rebar can all be preserved using the process.

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