Optimal Selection of Cathodic Protection Depending on Climatic Conditions

Selection of Cathodic Protection Systems

The selection of cathodic protection (CP) systems must consider multiple factors, including climatic conditions. Properly selected CP systems enhance the reliability of pipelines operating in the northern regions and reduce failures caused by corrosion.
Highly effective CP against soil (underground) corrosion ensures the long-term operational reliability of pipelines. Optimal selection of CP involves considering various factors, with climate playing a significant role. Maintaining the efficiency of comprehensive corrosion protection is achieved through selecting the correct operating modes, timely system commissioning, and others.

Failure to adhere to these standards negates the benefits of high-quality pipeline design and construction.

Cathodic protection is particularly critical for pipelines in the northern regions, especially in Scandinavia, North America and Northern Russia, due to the specific conditions of installation and operation and the increased difficulty of repair and restoration in case of failures.

Considerations for Marine Hydraulic Structures

Special attention must be given to the cathodic protection method for marine hydraulic structures. When designing and implementing impressed current cathodic protection, several factors directly influencing system performance must be considered:

• Hydrology of the area 
• Seasonal variations in salinity 
• Freshwater discharge from underground sources 
• Wind patterns and ice loads 

Such structures require equipment with enhanced resistance to:

• Chlorine compounds generated from seawater electrolysis 
• Wave loads and mechanical impact 
• High humidity, precipitation, and dew point fluctuations due to temperature swings

CP System Selection Models

Optimal CP system selection can be based on mathematical, empirical, or hybrid models:

• Mathematical modeling calculation for CP design of trunk pipelines (MP) and field pipelines (FP) is based on the Norwegian standard DNV-RP-B401 “Catodic protection design”
• Empirical modeling relies on data analysis from experiments or field measurements
• Hybrid models integrate both mathematical calculations and empirical data for more precise predictions

For data collection, survey forms are used:

• for CP of port structures 
• for external CP of casings 
• for external CP of storage tanks 
• for external CP of pipelines 
• for internal CP of aboveground tanks

Comprehensive Corrosion Protection

To ensure reliable underground corrosion protection, the following tasks must be addressed:

• Establish requirements for coatings that are essential for comprehensive soil corrosion protection
• Define protection criteria, balancing metal potential, acidity, protective current density, and temperature in the electrode area
• Develop an optimal cathodic protection system for underground pipelines in northern regions, considering permafrost layers
• Reduce impressed current anodes dispersion resistance and stabilize parameters across seasons
• Create an autonomous cathodic protection system using cast and extended anodes, considering thawing zones in winter
• Develop special regulatory documentation for the cathodic protection design, construction, and maintenance of northern and low-temperature pipelines

These tasks form the basis of a new research direction in CP for trunk pipelines. Timely implementation of these findings into gas and oil pipeline protection in the Arctic will ensure failure-free operation for the entire planned service life while delivering significant economic benefits.

Selecting Coating for Corrosion Protection

Choosing the correct coating type and structure is crucial for comprehensive cathodic protection, particularly in frozen, rocky, or swampy terrain. Any coating selection must be technically and economically justified at the design stage. Key coating parameters include:

• Compatibility with CP systems 
• Aging kinetics and durability, characterized by decreasing transition resistance and aging constant 
• Resistance to temperature fluctuations, ensuring adhesion to metal through freeze-thaw cycles 
• Protection against adhesion loss, as well as biochemical effects from soil microorganisms

Enhancing Coating Efficiency

Any organic-based coating, due to its natural porosity, cannot provide 100% underground corrosion protection. Micro-pores in coatings may trap corrosive electrolytes, initiating corrosion under the insulation. As corrosion progresses, iron oxidation products expand up to five times their original volume, breaking micro-pores and accelerating degradation.
The primary function of a pipeline coating is to minimize metal exposure to corrosive environments and stray currents. This optimizes CP effectiveness by allowing protective currents to focus on active zones.
In high-stress pipeline systems, coatings also play a key role in expanding cathodic protection coverage, allowing CP currents from a single anode groundbed to protect a larger area. In aging pipelines, this function can be maintained not only through repairs but also by reconfiguring the anode system, using flexible anodes instead of conventional point-source anodes (shallow horizontal or deep well anodes).