What is cathodic protection?

Cathodic protection is a method of protection of metal structures from corrosion. The metals from which these structures are made - usually steel - are susceptible to corrosion by an oxidative reaction when they are in frequent contact with water. The reaction involves surrendering to the electrons of the metal and is supported by traces of salts dissolved in water, causing water to act as an electrolyte. Corrosion can therefore be considered an electrochemical process. Cathodic protection changes the metal structure to the cathode - a positively charged electrode - by adjusting the electrochemical cell using an electrical metal as an anode, so the structure does not lose electrons to its surroundings.

This method of protection can be used on underground pipes and tanks; above -ground structures such as electric pylons; and partially submerged structures such as ships and drilling trains. It can also be used to protect steel bars in reinforced concrete. Metals that are more resistant to corrosion are more expensive than steel and may lack the necessary force so that steel protected by corrosion is the obvYKKE The best choice, although other metals that can corrode can also be protected in this way.

steel consists mainly of iron, which has a redox potential of -0.41 volts. This means that it will tend to lose electrons in an environment that has less negative redox potential, such as water that can come into contact with this metal in the form of rain, condensation or damp surrounding soil. The water droplets in contact with the iron form an electrochemical cell in which iron is oxidized by FE -> Fe

2 +

+ 2E

-. Ice II II (Fe

2 + ) move into a solution in water, while electrons flow through metal and on the edge of water, interaction of electrons, oxygen and water produces hydruoxide (oh

-

) ions of reactions: o 2 + 2h 2 4OH -. Negative hydroxide ions react with positive iron ions in water and createIts insoluble iron II hydroxide (Fe (OH) 2 ), which is then oxidized to iron III oxide (Fe 2 ), better known as SS.

There are two main methods of cathodic protection that seek to prevent this corrosion by providing an alternative electron source. In galvanic protection, a metal with a more negative redox potential is than a protected metal connected to a structure of an insulated wire and creates an anode. For this purpose, magnesium with a redox potential of -2.38 volts is often used -the more commonly used metals are aluminum and zinc. This procedure sets an electric cell with a current flowing from the anode to a structure that acts as a cathode. The anode loses electrons and is corroded; For this reason, it is Known as a "sacrificial anode".

The problem with galvanic cathodic protection is that the anode will eventually be corroded to a point where it no longer provides protection and needs to be replaced. The alternative cathodic protection system is amazed by contemporary cathodic protection (ICCP). ItIt is similar to the galvanic method, except that the power supply is used to create an electric current from the anode to the structure to be protected. Direct current (DC) is required, unlike AC current (AC), so a rectifier is used to convert AC to DC. This method provides much more lasting protection because the current is supplied externally instead of being generated by the anode's reaction with its surroundings, so the life of the anode increases significantly.