What do you understand by cathodic protection? What are the advantages and disadvantages of cathodic protection? What are cathodic protection used for? This are questions which are going to be discussed and answered in this article.
A cathodic protection system has many advantages. One of the primary advantages is that it can detect corrosion before electrical systems break down. This will help prevent blackouts as well as power outages.
Yet another advantage is that it can reduce the environmental impact of the system by polarizing atmospheric contaminants away from the area of deterioration and off into a harmless circuit which will not produce corrosion.
Cathodic protection is the process of protecting metals (such as with electrical or metal-coated concrete) from corrosion. Essentially, it involves passing a current through the metal to excite its surface and raise any free salts to the cathode (which is usually an inert material that does not corrode).
After this process has been completed, some of these disadvantages are gone. But there are still some unanswered questions that need to be addressed before we can fully understand what cathodic protection offers us. What follows is a detailed analysis of the advantages and disadvantages of cathodic protection that exist in relation to this very important topic.
What Is Cathodic Protection?
Cathodic protection can be defined as a technique and method used to prevent the corrosion of an electric or metal structure. This process is especially helpful with structures that are in salt water or at high tide areas.
As these structures require a lot of maintenance and care, this process is quite helpful. The main idea behind this process is to protect the metal from the corrosion. In other words, the energy which is received by the metal through electrical impulses is known as cathodic protection.
Cathodic protection uses electrochemistry to remove any unwanted buildup on any electrical and non-electrical metallic surfaces. Cathodic protection helps to defend against corrosion through an electrochemical reaction known as oxidation-reduction.
This process is beneficial to the metal because electrons which are trapped inside an electrically conductive material release the trapped electron energy. The conversion of these electrons into photons can be used to convert any undesired ions from being transported through the material.
Moreover, the process is also beneficial to the material because it can be utilized to raise the free salts out of solution so as to protect itself from corrosion. The discharge of electrolyte ions results in a buildup of salt deposits which may exist on a metal surface.
The concept or theory behind cathodic protection is that if certain metals are submerged in this electrolyte solutions, they will spontaneously generate an electric current inside these solutions and will develop an electrochemical reaction that stops any unwanted corrosion before it starts.
For corrosion to occur, four elements must be present: a host site from which current flows, a destination site where no current flows, a medium capable of conducting current (such as water, concrete, or soil), and a metal path between the host and destination site.
When a structure such as a steel structure is corroding, electrons will leave this metal surface to reduce the ions in the electrolyte. In other words, it will lead the way for ions to be oxidized or reduced. As long as an electrolyte is present and electron capture reactions are occurring, the metal surface will be protected from corrosion.
Metal surfaces that are exposed to air do not receive any protection from corrosion. When water or other electrolyte solutions are absent and no chemical reactions are occurring at the metal surface, oxygen and moisture free metals tend to rust. This is because the metal surface is devoid of electrons, which are needed to remove the unwanted ions from the electrolyte.
When an electrolyte has been kept at an optimum concentration and a metal surface is subjected to electrochemical reactions, these reactions will generate increased amounts of electrons which will not be able to freely move inside the electrolyte. This causes an oxidation process that occurs on the metal surface and eventually produces corrosion.
The corrosion process can occur over a long period of time or it can begin immediately, depending on how much corrosion energy is generated by these electrochemical reactions.
Who Uses Cathodic Protection?
Cathodic protection has a wide range of use. Cathodic protection is often used to mitigate corrosion damage to active metal surfaces. It is used all over the globe to protect pipelines, water treatment plants, above and underwater storage tanks, ship and boat hulls, offshore production platforms, reinforcement bars in concrete structures and piers, and more.
Additionally, cathodic protection is also used for protecting public water and sewer systems. To this end, many cities in the United States use cathodic protection to protect their water from contamination caused by corrosion.
Cathodic protection can also be beneficial in the case of exploration, construction of buildings and industrial plants. Cathodic protection also plays an important role in a wide range of fields such as defense, aerospace and industry.
Cathodic protection is mostly useful in industries that have corrosive conditions. Cathodic protection is applied in industry and commercial settings where corrosion can cause serious damage to the machinery and equipment being used.
Providing cathodic protection to assets that are in salt water or other corrosive environments is a very important task to take on as soon as it becomes possible and as per the requirements of these environments.
For example, cathodic protection is being used for high-strength concrete reinforcement stabilization where an ion exchange system for corrosion control and a cathodic voltage source are used to maintain steel reinforcement at a low level of corrosion without any loss of strength.
Furthermore, steel reinforced concrete structures are being protected from corrosion due to their chemical and physical characteristics.
In the case of petroleum and synthetic rubber manufacturing industries, cathodic protection is widely used in order to keep their equipment at a safe level of corrosion without any significant loss of yield.
Heading towards the next topic which are the advantages and disadvantages of cathodic protection, let’s have a look at the different types of cathodic protection we have.
Types Of Cathodic Protection
There are two basic types of cathodic protection which are ‘Galvanic’ and ‘Impressed Current Cathodic Protection’.
Galvanic protection is a process of applying zinc coating to the metal at risk (steel) to prevent corrosion. The coating is applied using an electrostatic charge as a current to the metal. The zinc coating is then separated from the metal within the steel structures by washing or rodding off the existing coating. The zinc coating will be replaced to prevent corrosion of the steel structure.
Impressed Current Cathodic Protection
Impressed current cathodic protection utilizes a DC power source and a galvanic cell to provide a protective coating on the steel to protect it from corrosion. The galvanic cell consists of two dissimilar metals that are immiscible with each other. One metal is zinc and the other metal is steel.
The DC current will flow between the two metals in order to establish an electrolytic reaction between these two metals at the cathode or zinc end of the galvanic cell. This reaction will produce a thin layer of insoluble metallic oxide coating which will protect the steel.
Two examples that use impressed current are sacrificial anodes and linear impressed current systems.
Moving to the next topic, now we have known the two basic types of cathodic protection, we will be looking into the advantages and disadvantages of cathodic protection.
Advantages And Disadvantages Of Cathodic Protection
Here, we will e looking into the advantages and disadvantages of cathodic protection but first, we will discuss the advantages of cathodic protection and then later the disadvantages.
Advantages Of Cathodic Protection
- Cathodic protection is used to prevent the corrosion of many types of metal structures which would otherwise be damaged by corrosion. In particular, cathodic protection is often used to prevent the damage of buried piping, storage tanks, ships and boats, offshore production platforms and more.
- Cathodic protection prevents a lower rate of wear down on metal surfaces that are normally prone to erosion. Corrosion may cause metal surfaces such as steel reinforcements in concrete structures, steel pipelines and reinforcement bars in concrete structures to deteriorate much faster than usual. This is a very common occurrence and may cause great problems in terms of both the quality and price of these structures.
- Cathodic protection also helps to maintain the maximum capacity of metal structures that are being protected by cathodic protection.
- Cathodic protection prevents corrosion damage to the structural integrity of many types of piping and piping systems, especially those systems that are located above underground water, ground water or saline water bodies.
Many people have experienced the bad effects that corrosion can have on their underground wells which often lead to an explosion getting out of control, polluting local soil and groundwater, polluting nearby soils and eventually leading to significant financial loss due to lawsuits.
Disadvantages Of Cathodic Protection
- Brand new metal structures, surfaces and pipelines can be damaged if these structures or surfaces are given too much of a negative charge by the protector (cathodic protection device).
If too much negative charge is applied to these structures, they may become over-protected which may result in a severe waste of power and may cause other problems such as polarization and galvanic corrosion to occur.
- Cathodic protection can cause serious health effects in the local environment from the toxic chemicals that are used during cathodic protection. These toxic chemicals often contain heavy metals such as lead, mercury and nickel or have harmful chemical compounds as part of their chemistry.
Another problem is that cathodic protection devices will often use high voltage sources which may be dangerous to some people who are living near the cathode end of these devices.
- Cathodic protection devices are very expensive and put a lot of strain on a site’s budgets when they need to be replaced over time.
In some instances, the alkaline properties of cathodic protection can damage the surrounding materials that are being protected by cathodic protection. This is a very common problem in areas where cathodic protection is used.
As we have seen in the above article, cathodic protection is a very important and useful process in order to protect the structural integrity of many types of metal structures. The reasons for using cathodic protection are many and varied but regardless of these reasons, there are some disadvantages and advantages of using cathodic protection as well.
The main advantage of cathodic protection is that it prevents damage to the structural integrity of otherwise damaged metal surfaces which would be broken by corrosion. Cathodic protection is a very effective process that can often help to prevent damage caused by corrosion.
Cathodic protection prevents iron, steel and other metals from corroding but there are times when cathodic protection may also cause some problems, such as the problem of over-protection.
Another problem with cathodic protection is that it can cause a lot of damage to the environment by using toxic chemicals which may be harmful to humans and other living things.