Computational Design of ICCP Systems: Lessons Learned and Future Directions

Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.

This study is to acquire the confirmation data regarding the impressed current cathodic protection (ICCP) system by using the variable resistor for reinforced concrete specimens for improvement in under-protected area of reinforced concrete specimens. The ICCP system is one of the most promising corrosion protection methods. The Effect of ICCP system can be changed at diverse conditions. Particularly, temperature and relative humidity plays a crucial role in the CP effect. It was possible to confirm the performance of ICCP system by the use of variable resistor in different relative humidity and temperature conditions. The CP potential and current were measured by potentiostat, and 4 hour depolarization potentials were measured after disconnecting with anode for 4 hours. To enhance the effect of cathodic protection system, seawater was used as an electrolyte. Used anode for ICCP system was mixed metal oxide (MMO) titanium. From this study, it could be confirmed that the CP potential and current were highly influenced by temperature and relative humidity, and the CP effect in under-protected area has been improved by the ICCP system using the variable resistor.

Impressed current cathodic protection (CP) for reinforced concrete structures is a proven technology which can provide long term corrosion prevention for marine structures if properly designed and installed. This technology has been applied to a large number of concrete structures in Australia over the past 30 years and it is the technology of choice for many asset owners for the protection of structures susceptible to chloride induced corrosion. While this technology has proven to be highly effective in providing corrosion protection to embedded steel reinforcement, in some cases, the maintenance and monitoring costs have been relatively high and this is often due to defects during the design and construction stage of the system. The review of performance of many operating CP systems in Australia has led to the conclusion that there are many areas of improvement which can be implemented to optimize the long term performance of impressed current CP systems. The areas of improvement include materials selection, design, installation and monitoring of CP systems. This paper will provide a case study of a major CP system operating in Australia for 15 years and will propose a series of changes to current practices which can be considered for implementation in the design, installation and monitoring stages of new impressed current cathodic protection systems in concrete.

The Arctic imposes unique challenges for design of cathodic protection (CP) systems for offshore structures. These include alternative structure designs, and environmental factors such as pack ice, high water resistivity, extreme tidal velocities and amplitudes, and severe weather. Traditional approaches to CP design for offshore structures are typically not suitable for service in Arctic conditions. Adaptations include almost exclusive use of impressed current or hybrid CP systems, versus traditional sacrificial anode designs, specialized anode deployment and cabling systems, and design of CP monitoring equipment suitable for Arctic conditions. The effect of Arctic conditions on CP current requirement, anode current output, anode material selection, anode configuration, cabling systems and power supplies is discussed. Case histories of specialized CP designs for offshore structures in the Russian Arctic and Cook Inlet are presented. These case histories include relevant CP design, construction, installation and operating details. Introduction Cathodic protection using distributed weld-on aluminum alloy anodes has become the offshore industry standard for corrosion control on immersed surfaces of offshore structures in most oil producing areas of the world. Aluminum anodes with a design life equal to the expected service life of the platform are welded to the structure in the fabrication yard. Use of coatings is typically limited to the splash zone areas and the inside of ballast tanks on floating structures. These stand-alone sacrificial anode systems are essentially maintenance free, except in the rare instances where anode retrofit is required to extend the platform service life. The use of impressed current cathodic protection (ICCP) systems is generally limited to floating vessels such as FPSOs or drill ships, and for anode retrofit. With respect to cathodic protection design, offshore structures located in Arctic/subArctic regions subject to the presence of sea ice, frigid temperatures and other extreme environmental conditions often require a different approach. The demands of the Arctic environment impact cathodic protection design in two general ways - electrochemically and mechanically. Electrochemical impacts include, but are not limited to, increased current requirement, higher seawater resistivity, reduced anode performance and higher rectifier voltage requirements. Mechanical affects are considered those that impact the design of cathodic protection hardware with respect to resistance to physical damage. These include the damage from ice impact and/or abrasion, freezing and wave/current forces. In some cases, mechanical and electrochemical effects are combined, as in the mechanical removal of calcareous deposits by ice or wave action, which increases current requirement.

The design of an impressed current cathodic protection (ICCP) system is influenced by the distribution of current and potential towards the different reinforcement layers of a reinforced concrete (RC) structure. To enhance ICCP efficiency, numerical simulations are crucial for predicting current distribution and optimizing the system performance, material use, and costs. This research investigates the effect of the chloride concentration on the performance of an ICCP system using a TiMMO mesh anode in a mortar overlay. Two concrete specimens, both with two reinforcement layers, are the subject of this study. The chloride content is being varied, using 2 % and 3 % mass by weight of cement. Using the finite element method (FEM), simulations of current and potential distribution within these elements are conducted and validated against the experimental results. Both stationary and time-dependent studies are performed to evaluate the impact of temperature and the internal concrete humidity on the cathodic protection system over time. These findings provide key insights into the performance and behaviour of ICCP systems.

Corrosion damage is a major factor in ship maintenance and availability. Paints and shipboard impressed current cathodic protection (ICCP) systems are important established tools in the reduction of corrosion damage to ships. The design of cathodic protection systems is of interest to defence organisations not only to protect the integrity of the ship but also because of the electric fields generated in the sea water by the ICCP system. Recent developments in computer simulation techniques based on the boundary element method has enabled the electric fields generated by the galvanic interaction of the ship metallic structure and the sea water to be predicted. Thus providing a tool to predict changes in the protection level of the ship and the electric field in the seawater caused by modification to the ICCP system. In a previous paper techniques for minimisation of the electric field were studied by placing several anodes on the hull of the vessel [1] and automatically adjusting the anode current. In this paper the electric field is minimised by moving the position of the anode as well as changing the current. The proposed approach uses source points to represent the anodes.

The Impressed Current Cathodic Protection (ICCP) System is a corrosion control method where there is a flow of electrons to a metal structure, thus protecting it. As a ship owner, the EMP Malacca Strait SA used a coating method combined with the ICCP system to control corrosion on the Ladinda FSO. However, nowadays, the Ladinda FSO is known to carry a decreased volume of oil cargo due to declining oil production. This results in a change in the wetted area on the tanker’s hull in the design conditions of the ICCP system from early 1983 to the current conditions (2010) that affect the current magnitude of the protection given. This leads to an over- protection that destroys the coating layer. To avoid over-protection on the hull of the Ladinda FSO, an analysis and redesign of the ICCP system has been conducted. In the redesign of the cathodic protection system on the Ladinda FSO, the NACE Standard RP 0176- 2003 "Corrosion Control of Steel Fixed Offshore Structures Associated with Petroleum Production" was used as a basic reference in the design. The first step was to make the initial ICCP system design and then rebuild the initial ICCP system design for cathodic protection according to recent conditions. Next, the new design was analyzed and the results are the recommendations. The monitoring system was also redesigned to maintain proper control at a range of–1100 mV to–800 mV vs. Ag/AgCl/seawater. The new design will needs two transformer rectifier units as the power supply, which will give sufficient voltage to drive six titanium anodes coated with mixed metal oxide (MMO). The capacity of each transformer rectifier is 236.25 kV.A with a DC current of 21 A and DC voltage of 9 V. Four potential test boxes featuring Ag/AgCl reference electrodes and the "Protection Current Control Program" as the control system and monitoring system are added in this new ICCP system design.

This paper discusses the case study of the impressed current cathodic protection (ICCP) system for jetty of barge loading conveyor (BLC). This impressed current cathodic protection system is corrosion mitigation using an inert anode and an electrical device: rectifier, voltmeter, DC source on the BLC structure, and jetty pile to provide accelerated corrosion protection to parts of the pipe submerged in seawater. In this study, a mapping of the service distribution of inert anode carried out so that it can protect the BLC structure and the pile. The results of the measurement of the structure potential and impressed current cathodic protection (ICCP) at BLC jetty considered to meet the protection criteria according to ISO 15589-2: 2012 standards. The obtained measurement results are in the range between -842 mV to -1197 mV (Ag/AgCl). The results of inspections and measurement of the output of the transformer rectifier show the total output current is safe.

This paper introduces an innovative improvement to impressed current cathodic protection (ICCP) systems by integrating a pulse-feeding technique designed to address metal protection degradation during off-potential periods, a common issue in conventional systems. The proposed system enhances the overall effectiveness and reliability of ICCP, providing consistent corrosion protection for critical metal structures. A notable advantage of this method is its simplicity, utilizing a cost-effective microcontroller for pulse feeding. This approach simplifies integration processes and enhances cost-effectiveness, making it an attractive solution for improving cathodic protection system performance without substantial additional costs. The method addresses conventional ICCP weaknesses by applying a high-frequency pulse current during off-potential periods. This reduces excessive negative charge buildup on metal surfaces during interruptions, boosting the system’s effectiveness and stability. Research laboratory experiments were conducted using pulse width modulation (PWM) on an ATmega328P microcontroller to demonstrate the method’s effectiveness. Additionally, an IoT-monitored ICCP system was developed using an ESP32 microcontroller and the Blynk application. Results highlight the superiority of a 50 kHz pulse feeding frequency in preventing corrosion compared to lower frequencies. Overall, this advancement significantly enhances ICCP systems, providing improved corrosion protection and durability in harsh environments.

The use of Impressed Current Cathodic Protection (ICCP) systems in large crude carriers such as very large crude carriers (VLCC) and ultra large crude carriers (ULCC) is universally regarded as an effective means of corrosion protection. However, traditional ICCP systems have certain drawbacks that can be overcome by using data-driven methodologies. This research describes a unique data-driven ICCP system aimed to optimise energy consumption and ICCP system efficacy for large crude carriers. The objective of this project was to develop an AI-based ICCP system that could address existing ICCP system shortcomings such as overprotection, inefficiency, maintenance, corrosion detection, and environmental factors. To achieve this objective, we employed a machine learning approach that utilized historical data to train our AI-based ICCP system. Our methodology involved collecting data on the environmental conditions, the ICCP system output, and the corrosion rates for several large crude carriers. We then utilised this data to train machine learning algorithms that could anticipate the best current output needed to protect the hull while consuming the least amount of energy. The procedures involved testing the AI-based ICCP system in a simulated setting. Our study shows that the data-driven ICCP system provides significant benefits for the corrosion protection of large crude carriers. Our results demonstrate that the AI-ML approach is effective in reducing overprotection and optimizing energy consumption, while also predicting maintenance requirements, detecting localized corrosion, and adjusting the ICCP system output based on real-time environmental data. Our observations show that the data-driven ICCP system is able to detect localized corrosion more accurately than traditional ICCP systems, which can lead to early detection and prevention of corrosion. The system is also able to adjust the current output based on real-time environmental data, providing better protection against external factors such as temperature, salinity, and currents. This research describes a revolutionary data-driven approach to ICCP systems that tackles the shortcomings of standard ICCP systems used in large crude carriers. Our research delivers new insights into optimising energy consumption, reducing overprotection, forecasting maintenance requirements, identifying localised corrosion, and changing the ICCP system output based on real-time environmental data by utilising AI-ML technologies. These results have the potential to significantly help the oil and gas industry by improving the efficiency and effectiveness of corrosion prevention for large crude transporters.

Grounding grid is an indispensable important component in the substation, which has important meaning for protecting the personal safety, equipment safety and system safety. Due to the grounding grid is always in the complex soil, it faced the varying degrees of corrosion threat. When the soil resistivity is high, engineers usually use an impressed current cathodic protection (ICCP) system to suppress corrosion. But the existing design and installation process of ICCP systems has some drawbacks. Engineers can only get the effect of the system after ICCP systems installed and run. If the effect is not up to standard, they need to re-design and re-install, which will waste a lot of manpower and resources. This paper mainly analyses the ICCP systems and proposes a new method to design the substation grounding grid ICCP systems by COMSOL Multiphyscis simulation software, which can effectively solve the above problems.

Design considerations for cathodic protection systems of seawater applications have been changing in the past 20 years, because Impressed Current Cathodic Protection (ICCP)systems have made a big development in the last decades. Nowadays ICCP systems offer a lot of monitoring and control features. Today a gradual shift from sacrificial anode systems to Impressed Current Cathodic Protection (ICCP) systems can therefore been recognized. From a general point of view ICCP systems are better performing than sacrificial anode systems, but the performance is strongly dependent on the number of anodes and rectifiers being used, thereby impacting heavily on the total installation cost of the ICCP system. A computer aided ICCP system design allows to optimize the performance of the ICCP system while keeping the total number of anodes and rectifiers as limited as possible. The paper presented here describes an ICCP system that was applied for the first time to a bare steel offshore platform(1). Computer modeling simulations for predicting the local protection level on the submerged surfaces of this structure have enabled the design of an optimized ICCP system configuration that was successfully installed into the field. This presentation will describe the performance of an intermediate design stage of the ICCP system as predicted from the computer simulations and discuss the specifics of the simulation method. It will be demonstrated that the computer simulation results can provide an indication on how to improve the ICCP system design.

Impressed Current Cathodic Protection (ICCP) is a widely utilised method for safeguarding reinforced concrete (RC) structures, including bridges, in marine environments. However, certain ICCP systems encounter degradation of the backfill mortar caused by acid formation at the anode. The acid produced reacts with the anode backfill mortar, compromising the functioning of the cathodic protection system. Rectifying the acidification issue typically involves replacing the backfill mortar and, in some cases, even the anode when it is negatively impacted by acid attack. This paper presents, for the first time, a specialised sustainable cementitious matrix that exhibits excellent acid resistance, intended for use as the anode's backfill material in ICCP systems. The proposed mortar effectively mitigates the effects of acidification around the anode, significantly enhancing the durability of the mortar and, consequently, the service life of bridges equipped with ICCP systems. The mechanical and durability performance of the mortar in an acidic environment is evaluated through various tests, including gravimetric analysis, dimensional changes, diffusion depth, compressive strength, direct tension, slant shear, impact resistance, and interface integrity assessments. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques are employed to investigate the material's performance. Subsequently, the specialised mortar is applied to cover Mixed Metal Oxide (MMO) activated titanium mesh anodes of the ICCP system in a reinforced concrete bridge, while its performance is continuously monitored. The results demonstrate that the proposed mortar effectively eliminates acidification issues and improves the performance and longevity of ICCP systems in harsh marine environments.

With the aid of the boundary element method, this paper presents an efficient design and evaluation tool of the impressed-current cathodic protection (ICCP) system for a ship hull. Desirable working state of ICCP system is obtained by the control of anode current, monitoring the potential of reference electrode. Converting impressed-current anodes to concentrated internal point sources, the Poisson's equation becomes available to express electric behavior in cell. In the present approach, not only potential and current densities on boundary but also the electric current from anode points and the set potential of the reference electrode can be calculated. The proposed methodology is applied to a practical container ship protected by an ICCP system. Based on the results of analysis, rational design of ICCP system for ship hull becomes possible.

The goal of impressed current cathodic protection (ICCP) design for ship hulls, under the Navy Ship's Technical Manual (NSTM, Chapter 633), is to provide a uniform potential distribution at -0.85 V, ± 0.05 V, versus a silver/silver chloride (Ag/AgCl) reference cell, over the wetted hull surface during all operational aspects of an active ship. To accomplish this, the physical scale modeling (PSM) technique, combined with a rigid design protocol, has been used extensively by the U.S. Navy to provide optimal and retrofit upgrade designs of ICCP systems for hulls. The ICCP design guidance, provided by the protocol, defines the hull properties, hull damage and general power supply requirements. PSM is utilized to determine optimal placement of ICCP components (anodes and reference cells) and to evaluate performance for up to a 15% wetted hull coatings loss under static (pierside) and dynamic (underway) conditions. Data are provided which illustrate the use of the design protocol criteria, along with the integrated PSM technique, to determine ICCP system design and evaluate performance.