Cathodic Protection Extending the Life of Critical Infrastructure

Feb 04,2020

Cathodic protection continues to defy gravity on the back of rising demand for corrosion prevention procedures as an important element of asset-protection strategy. The trend is likely to prevail in line with increasing construction and infrastructure development projects worldwide, particularly in developing regions. Moreover, governments in various countries are dedicating a significant chunk of their total budget in upgradation and development activities, which are further fueling the popularity of cathodic protection.

Corrosion is among the major threats to the prolonged integrity and profitability of assets, accounting for nearly 4% of the overall global GDP. Ships, offshore wind turbines, flood gates, harbor installations, and other structures require effective shielding from corrosion. Failure in doing so can have a negative impact on ROI due to upsurge in maintenance expenses. It can also result in loss of lives, and in turn, brings the reputation of a company at stake. As such, cathodic protection methods must be considered a priority during planning, engineering, production and operation of these infrastructure assets.

 Ideal Cathodic Protection Method in Oil & Gas Pipelines

Underground pipeline network, conveying natural gas and liquid petroleum products is the key aspect of various civil facilities and infrastructure. For a majority of oil & gas terminals all over the world, protection of pipelines is essential. In oil & gas pipeline systems, cathodic protection can be done in two ways, either using an exterior galvanic anode or an exterior DC power source (rectified AC) to impress a current via an exterior anode (generally inert) onto the pipeline surface.   

The former approach, galvanic systems, offers the benefits of low operating expenses, minimum maintenance requirements, and straightforward installation. In addition to these, galvanic systems do not require an external power supply and they pose minor impact on foreign buildings. But having said that, their application is limited to localized CP purposes as they provide inadequate protection to large buildings.

On the flip side, impressed current cathodic protection (ICCP) finds immense utilization in the protection of pipelines and underground storage reservoirs. Owing to its excellent current output, ICCP is a great fit in protecting large underground metal framework cost-effectively, as well as is capable to withstand extreme conditions and soil resistivity. Nevertheless, the performance of ICCP is linearly associated with the continuity of their AC power source, and thus, can have a possible effect on the neighboring buried structures.

The degree of CP current applied from ICCP is vital; too less current will result in corrosion adversaries, while too much current can cause dismantling of the coating and hydrogen embrittlement. On these grounds, impressed current cathodic protection systems accent for regular monitoring.

As the oil & gas sector is following an upward trajectory, globally, cathodic protection continues to be the conventional method for protection of pipelines, offshore oil platforms, and other metallic structures. However, it is paramount to know the basics of corrosion to ensure efficient implementation of cathodic protection. Opting for the appropriate cathodic protection technique depends on numerous factors such as cost-benefits and the dimensions of the structure to be protected.

Cathodic Protection a Sustainable Approach in Preserving Concrete Structures

A main reason behind concrete deterioration is corrosion of embedded metals and substances especially, reinforcing steel, epoxy-coated steel, and pre-stressed concrete. And when left unnoticed, corrosion of these materials can, in due course, trigger major structure replacement or rehabilitation costs. For long-term solution, cathodic protection methods are considered ideal to enhance the durability of new and existing concrete structures.

Designed as per the National Association of Corrosion Engineers (NACE) international standards, ICCP contains permanent inert galvanic anodes – electrically conductive coatings or ceramics – and an exterior DC power supply, which are efficient in delivering adequate current to the steel to curb the corrosion of concrete.

In marine or salt water settings, concrete and steel piles are susceptible to critical corrosion deterioration. For marine concrete protection, galvanic jacket systems are preferred to offer galvanic cathodic protection for conventionally reinforced steel piles and concrete. Galvanic jackets usually incorporate distributed alkali–activated anodes, and zinc mesh anodes in wicking layer for direct contact of the seawater with the zinc inside the concrete jacket.

For many infrastructure owners and engineers confronting cost upheaval and interruptions due to maintenance and repair of concrete corrosion, there is a financial reward to sustain and extend the service life of existing concrete structures from further corrosion damage. Also, preserving huge concrete structures including, marine piers, bridges, and parking garages, is a sustainable approach with environmental and public advantages.

There are various types of cathodic protection available to protect new and existing concrete structures, with each of them providing different scales of corrosion protection and cost. Getting familiarized with the capabilities and drawbacks encourages owners and engineers to employ the ideal cathodic protection system for their individual concrete preservation practice.

Internal and External Cathodic Protection in Above Ground Water Storage Tanks

Carbon steel water storage tanks are commonplace in many municipal water systems. When it comes to steel structures, corrosion is an ever-existing issue and causes early failures and disruptions in operation during repair works. Although coating systems are considered a primary defense option against corrosion on the interior wetted areas of water storage tanks, they are subject to degradation over time.

Deploying a cathodic protection is a common means of complementing the coating layer inside water storage tanks. If properly applied and maintained, coating system, coupled with CP, helps inhibit the corrosion cycle. There are various factors influencing the design of internal CP systems including, coating quality, water quality, shelf life of desired anode, and freeze potential.

Exterior tank bottoms are also prone to corrosion due to their contact with the ground base. To address the situation, impressed current cathodic protection is the accepted engineering design to shield the tank bottom owing to their benefits over galvanic systems. A usual approach in exterior tank bottom CP systems is using linear anodes in concentric circles.

The key advantage of the linear assembly is that everything below the tank is assembled and checked before installation and the only thing required is to place the anode system as per the blueprints and manuals. This makes installation exceptionally easy while ensuring optimum system reliability and minimal operating costs.

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