Corrosion control of infrastructure using cathodic corrosion protection

Material loss due to deterioration cause by electrochemical reaction is one of the biggest challenges to our aging infrastructure nowadays. In a simple word, these steel based infrastructures facing the corrosion problem.As per studies from several governments, it costs more than $400 billion of loss annually due to corrosion problem in the US alone.

With science and technology, we can actually prevented these huge amount of loss. One of the proven science and technology methodology that can extend the life of our steel based infrastructure is cathodic corrosion protection. Cathodic protection system usually installed to the pipes, storage tanks, vessels and even underground embedded steel piling. The environment can also be protected from the pollution of hazardous materials, liquid or gases due to the loss of materials from corrosion process. Corroding materials can also cause injury due to sharp edges produced and somemore those rusty surface of infrastructures projected ugly scenary to the surrounding environment.

Electrochemical reaction took place when a metallic structures are place in electrolytes (soil or waters). There will be anodic and cathodic areas on the surface of the structure due to the reaction with the environment. Corroding areas known as anodic (lose current) while the area which is not corrode known as cathodic(gain current). The above explaination make researchers thinks that the whole structure of a metallic body can be protected from corrosion, if it become cathodic (gain current).

Cathodic protection works when there's an external source of DC current supplied to the corroding structures.Let say if an underground pipeline receive an external DC current it'll become cathodic. An external DC current source can be from sacrificial anode (for example Magnesium, Zinc, Aluminium) or impressed current from transformer rectifier. Sacrificial anodes are metals which have higher tendency to release electron compared to steel. Impressed current system is when a transformer rectifier force current to flow via an inert metal. The induced DC current will replaced current release to the corroding structure, therefore no corrosion occured. Cathodic corrosion protection can only work if there are anode, cathode, electrolyte and a metallic path.

The replacement cost of an infrastructure which is not installed with cathodic protection are very high compared to the maintenance by using cathodic protection system. Therefore, a cathodic protection specialist offered a system which is cost effective . These can be accomplished by a proper cathodic protection system design, procedures and research. The cathodic protection techniques had been discoverd and commerciallized since 1930's .

The National Association of Corrosion Engineer (NACE) is and organization recognized around the world for their expertised in corrosion control. They conducted training and certification for players in the industry.

The following industries are served by professional from NACE:

* Power and Energy
* Independent and General Contractors
* Architectural and Engineering Firms
* Water and Wastewater Municipalities
* Oil and Gas Industries
* The Federal Government
* Alternative/Clean Energy
* Lite Rail Systems (DC) and High Speed Trains
* Mobile Home Parks
* Service Stations
* All other Infrastructure and Industries
* Above and Below Grade Storage Tanks (Water, Chemical, Petroleum, etc.)

Some of the structures that can be considered for cathodic protection may include but are not limited to the following:

* Above Grade & Buried Pipelines of All Types (DIP, CCP, PCCP, Carbon Steel, PVC, etc.). Chemical, Petroleum and Water Pipes
* Marine Structures such as Mooring Dolphins, Sea Walls, Pipe Piles, Offshore Platforms and more
* Reinforced Concrete Structures
* Submerged (Internal) and Soil-Side Surfaces for Storage Tanks
* Lite Rail Systems and High Speed Trains
* Well Casings
* Intake Structures, Water Boxes and Other Structures at Power Plants
* Clarifiers, Trash Racks, Sludge Thickening Tanks and Other Structures at Water and Wastewater Treatment Plants
* Submerged Pumps and Piping at Pump Stations
* Electrical Grounding Systems at Satellite Towers and Other Locations
* Buried cables
* All Other Related Metallic and Reinforced Concrete Structures

Cathodic corrosion protection is the proven techniques for decades though the process can't be seen from the naked eye. Cost of replacement of a metellic infrastructure due to corrosion problem can be minimized by a proper maintenance and installation of cathodic protection system. An effective cathodic protection system is when it was installed together with the best coating system in the market.

Corrosion in Metals - Principles and Prevention

Corrosion

The tendency of metals to return to their natural condition is known as corrosion process, the deterioration of metals by abandoning their current physical form due to the electrochemical reactions.

The electrochemical reaction occur with the existence of electrolytes, conductor and metals. In high humidity environment, with the presence of liquid/water in atmosphere this electrochemical reaction occurred on steel structures. The same process applies on structures immersed in the water or buried underground.

Metals corrosion occur due to the tendency to be more thermodynamically stable with the combination of oxygen in the atmosphere. The materials then metallurgical transformed to a different state with the supply of electric, chemical or heat work.

Oxidation is a chemical process where metals oxidized. Oxidation of a metal occurred when it discharge electrons. The rate of electrons discharge depends on the metals' affinity with oxygen, gold and platinum hardly discharge since they have low affinity with oxygen. An example of metal with high affinity of oxygen is iron.

There are 3 types of corrosion:-

i. Generalized corrosion

This type of corrosion mostly effect on the surface of metals and the metal lost can be considered slow, usually classified as non severe and depends on the contact with electrolytes and types of electrolytes contacted.

ii. Localized corrosion

The localized corrosion occurred on a specific location within the metal structure. It cause cavity formation. These cavities known as ulcers, craters, pittings, or criccas depends on their size and depth. Localized corrosion can be classified as severe since it have the tendency to penetrate. The cricca or fissure can be intergranular or transgranular, depending if it follows the edge of the grain or through it.

iii.Selective corrosion

Selective corrosion produces the preferential dissolution of a certain part of the metal that, for chemical or metallographic reasons, proves to be more easily attackable.

We can speak of cristalographic, intergranular or interdendritic corrosion, if the corroded material results in certain crystalline species in the grain borders or the immediately adjacent zone.

Another form of selective corrosion, the dealloying, happens when the preferential dissolution of one of two components of an alloy is verified, leaving an inconsistent and frothy residue of the other metal in the alloy.

Corrosion control and prevention:

There were few method use to control and prevent corrosion in the industry.

i. Some contractors use special construction materials resistant to corrosion.

ii. Use paint specially produce for corrosion protection, eg:- International Paint, Belzona etc

iii. Cathodic protection system.

iv. Corrosion inhibitor.

v. Anti corrosive system