Impressed Current Cathodic Protection Research Articles

Corrosion behavior of austenitic stainless steel and nickel-based welded joints in underwater wet welding

Marine structures such as ports, bridges, pipelines, vessels, and platforms are an essential part of modern infrastructure, where the use of higher-strength steel provides savings in logistics and construction. However, the repair of higher-strength steels can be challenging, especially underwater. Wet shielded metal arc welding is the most widely used and least expensive method for underwater welding repairs, but is very susceptible to hydrogen-induced cracking. Thus, researchers and welding engineers aim to reduce the amount of hydrogen in the weld material. Recent success has been achieved through the use of austenitic welding consumables, such as austenitic stainless steel and nickel-based electrodes. The use of these consumables drastically reduces the amount of diffusible hydrogen in the weld metal. However, these austenitic materials usually have different corrosion potential as compared to the structural steel the weld beads are applied to. This creates the risk of severe galvanic corrosion. In the presented study, the corrosion behavior of welds created with austenitic stainless steel and nickel-based electrodes were studied. Samples were aged for 1.5 years in the Baltic Sea. Simultaneously, the effectiveness of corrosion protection systems such as coating and Impressed Current Cathodic Protection (ICCP) were evaluated. Localized corrosion occurred in the heat-affected zone when austenitic electrodes were used in the corrosive environment. The localized corrosion depth after 1.5 years in the Baltic Sea and in the salt spray layer was approximately 250 µm and 390 µm, respectively. The ICCP system and the use of a coating were effective in preventing localized corrosion. The low pitting corrosion density of 2.5 × 103 m−2 corresponds to grade A1 according to the standard and was found to be negligible as compared to the localized corrosion in the heat-affect zone.

Evaluation of the acoustic performance of a novelty cathodic protection system against guitar steel strings corrosion

This work was conducted to establish the efficiency of an impressed current cathodic protection system for musical instruments’ steel strings in protecting them from corrosion caused by human sweat. To conduct this research, the harmonic content degradation of a guitar string subjected to different corrosion stages by artificial human sweat, with and without cathodic protection by an impressed current, was studied. String corrosion is characterised by not only the electrochemical technique of polarisation resistance, but also by weight loss by gravimetric measurements and FESEM microscopy. From the correlation between the acoustic and electrochemical results, it can be concluded that harmonic content degradation of guitar strings increases corrosion but is less significant in the strings protected by impressed current.

Corrosion protection failure test analysis of the initial damaged cable ICCP mechanism

Given the corrosion protection failure of the cable-stayed bridge cable in the actual project, the impressed current cathodic protection (ICCP) technology was used to carry out the anti-corrosion tests from steel wire scale to cable scale, analyze the corrosion protection characteristics of steel wire ICCP, deduce the corrosion factor ICCP diffusion model, and reveal the space ICCP mechanism of the initial damaged cable. The analysis shows that ICCP can effectively inhibit the corrosive effect of steel wires and cables, and reduce the loss of mechanical properties of steel wires. Its protective efficiency increases with an increase in the absolute value of its protective potential and decreases with an increase in the dead load level. ICCP has a blocking effect on the diffusion of corrosion factors in the cable space, and the corrosion spatial distribution range, corrosion factor concentration, and diffusion coefficient of the initial damaged cable decrease significantly with the increase in the absolute value of the protection potential. The open circuit potential moves in a positive direction with the development of the corrosion process, and the blocking effect of corrosive factor diffusion is transformed from the joint participation by sacrificial anode cathodic protection and ICCP to the dominance of ICCP.

Shedding Light on the Failure Factors of Subsea Critical Fastener Bolts

Offshore facilities, such as oil and gas rigs, wind turbines, and related subsea equipment, typically use flanges fastened using bolts and nuts as the main connectors. In this study, multidisciplinary parameters, namely the preload torque used to tighten bolts, simulated subsea water currents, water temperature, and impressed current cathodic protection, were applied to ASTM A193 B7 bolts. An experimental supervisory control and data acquisition system was designed to obtain measurements every 5 min throughout a 21-day experiment. Finite element analysis was performed to predict the structurally vulnerable areas of the bolts. A strong correlation was found between the reference electrode readings and the measured electrical current, tightening torque, and water temperature. As the water temperature rises during the day, the reference electrode reading becomes less negative and the electrical current decreases. Subsea water currents cause about a four-time increase in the bolt corrosion rate, with unprotected bolts suffering a nine-time-higher corrosion rate than protected bolts. A unique supply–demand interaction is observed; less protection is supplied to areas with lower corrosion rates (lower demand for protection). Finally, scanning electron microscopy examination reveals new insights into the failure mechanisms of subsea bolts.

Anticorrosion Method Combining Impressed Current Cathodic Protection and Coatings in Marine Atmospheric Environment

In this study, a new anticorrosion method combining impressed current cathodic protection (ICCP) with coatings that can be applied to marine atmospheric environments is proposed. As the corrosion medium fills the cracks and pores of the coating, an electrolyte film layer is inevitably formed on the metal surface. Therefore, a graphene conductive coating with excellent chemical inertness and shielding performance is selected as the intermediate coating to form an electrolytic cell system with a metal substrate serving as the cathode and a graphene coating serving as the auxiliary anode. By studying the surface corrosion morphologies and electrochemical signals of the coating samples at different protection potentials and coating thicknesses, the optimal potential is determined to be 0.6 V, and the optimal coating thickness is determined to be 20 μm. The samples protected by the joint method have lower corrosion rates and better anticorrosion performance than those protected by the coatings alone.

IoT for Cathodic Protection System as Iron Concrete’s Corrosion Protection

Iron concrete or reinforcement steel is steel used for reinforcement of concrete construction or known as reinforced concrete. Iron concrete can undergo a corrosion process caused by chemical or electrochemical reactions between reinforcement steel and its environment. One way to protect concrete from corrosion is cathodic protection. There are two types of cathodic protection, namely sacrificial anodes and impressed current cathodic protection (ICCP). ICCP is more commonly used for protection in reinforced concrete structures. In ICCP, negative current flows to the iron concrete and positive current flows to the anode. This is to protect the concrete from corrosion. In addition to the corrosion protection system, there is also a half-cell potential test to measure the chance of corrosion of the concrete. The project used IoT to monitor and control the ICCP. Measurements are made by reading the potential difference between the reference electrode and the iron concrete. The probability of corrosion can be determined by reading the corrosion probability table with ASTM C879-09 standard. The ICCP system in general still uses the manual method so that there are time efficiency problems in controlling the voltage and current for ICCP purposes, cannot schedule the provision of electric current and monitor it at any time, especially if the electric current flowing in the concrete is higher than the standard it should be. Based on the results of the tests carried out, the IoT system can regulate the power supply by setting the voltage and current and can schedule the power supply to provide electric current to the iron concrete and can provide notifications if the electric current flowing in the concrete is more than or less than ICCP standard.

Experiments on shear behavior of reinforced concrete continuous beams strengthened by C‐FRCM

AbstractThe dual‐function retrofitting system that uses the carbon‐fabric reinforced cementitious matrix (C‐FRCM) as both the anode of impressed current cathodic protection (ICCP) system and the structural strengthening (SS) material, that is, an ICCP‐SS system, is investigated. The experimental program mainly focused on the shear behavior of C‐FRCM strengthened reinforced concrete (RC) continuous beam under the dual‐function retrofitting system. The influence of anode polarization on the shear strengthening of RC continuous beams is analyzed. Shear tests were conducted on a total of 14 corroded RC continuous beams to investigate the influence of key parameters, including anode polarization degree of prefabricated C‐FRCM plate, layer of carbon fiber mesh and side‐wrapping. The failure modes, shear capacities, and load‐deflection curves of the shear‐strengthened RC continuous beams are reported. Based on the test results, the applicability of relevant design codes was evaluated and found to provide rather conservative predictions for the shear capacity of the examined C‐FRCM strengthened RC continuous beams.

Comparative study of special iron-silicon-chromium alloy electrode (FeSiCr) and Zinc electrode (Zn)

Corrosion is an oxidation-reduction reaction that occurs mainly in metals in contact and with different potential energies, both subjected to an environment conducive to the circulation of electrons or ions. A widely used method for protecting metals is cathodic protection, which can be galvanic cathodic protection or impressed current cathodic protection. The structure to be protected by cathodic protection is called the cathode and the other metal that will suffer the sacrifice of donating electrons and being worn out is the anode, normally called the sacrificial anode. There are several types of materials that are used as anodes. Zinc (Zn) is a metal highly recommended as an anode for protecting vessels due to its ease of installation and maintenance. Another material used in cathodic protection as an anode is Iron-Silicon-Chrome (FeSiCr), which is a special alloy, considered inert. Comparing the Zn electrode with the FeSiCr electrode for cathodic protection of buried steel pipes, it can be concluded that the FeSiCr electrode is more efficient. The most relevant factor when comparing the two electrodes in the same condition is their material loss rate.

Efficiency of the Impressed Current Cathodic Protection (ICCP) in reinforced concretes: Experimental and numerical investigation

In the present work, the efficiency of the Impressed Current Cathodic Protection (ICCP) applied to reinforced concretes is investigated. A comprehensive approach, combining experimental and numerical methodologies, is employed. The investigation focuses on a simplified system, represented by a reinforced concrete slab subjected to accelerated corrosion.Experimental tests are conducted to evaluate the initial condition of the system and subsequently examine different ICCP scenarios. Various parameters are considered, including the spatial arrangement of reference electrodes and activated titanium anodes, as well as the applied current intensity. The outcomes of these experiments are carefully analyzed to assess the influence of these parameters, and the results are presented for in-depth discussion.Finally, a theoretical model based on electrochemical interactions between the steel and the concrete is developed thanks to virtual work principle. Applied to the system under study, the predictions of the model are shown to give satisfactory results when compared to experimental data, demonstrating its reliability.

Application of impressed current cathodic protection on chain structure: An experimental study combined with COMSOL simulation

Corrosion protection of mooring chain is difficult but of great significance to guarantee the security of deep-sea operation. In consideration of the advantages and limitation of impressed current cathodic protection (ICCP), the feasibility of ICCP application on chain structure was studied through physical experiments combining with COMSOL simulation. The influence of electrical continuity on the protection potential distribution was investigated by potential measurement and numerical simulation. It was demonstrated that the conductivity was the key factor restricting the successful application of ICCP on the chain structure. With improved electrical continuity, the surface potential distribution of the chain structure under ICCP was uniform with a difference less than 12 mV, and the 90-day corrosion rate significantly reduced by 94.8% compared with that without ICCP. Furthermore, the quantitative formula of the relationship between the critical conductivity required for ICCP and the chain diameter was determined to be σc = 0.015d2 + 0.65d + 10.49. The effect of corrosion time and auxiliary anode distance on the potential distribution was also investigated. This work might provide new idea for the corrosion protection of mooring chain and provide reference for the design of mooring chain with improved possibility in corrosion protection.

Development of a novel and specialised cementitious matrix overlay for anode embedment in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges

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.

Corrosion prevention of storage tank bottom using impressed current cathodic protection – Experimental and simulation study

Underside failure of storage tank bottoms is a serious industrial problem which is induced by various corrosion phenomena such as under deposit, microbial and stray current corrosion and can lead to leakage of hazardous materials and explosion. Impressed current cathodic protection (ICCP) is a widely used technique to hinder these types of corrosion. However, undue design of the ICCP system can accelerate the corrosion. Therefore, it is necessary to make sure that the tank bottom is totally and properly under protection before implementation. For this aim, a FEM model is designed in this study for validating this presumption. The model is based on the potential and current density distribution of the tank bottom and is designed using the data of a real storage tank being protected in practice. Simulation results showed that the tank bottom's potential with the ICCP applied (considering voltage drop) and its polarized potential at the very first instant of current interruption both are at least −0.850 V vs Cu/CuSO4. Furthermore, based on the calculations, 0.260 to 0.280 V polarization is experienced by the tank bottom. These results confirm full protection of the tank bottom. Effects of anode arrangement, coating application and soil resistance on the system performance are also investigated and the most optimal design is proposed based on the potential distribution. Conducting such a simulation in advance can significantly increase the life time of the structure.

Carbon enhanced cementitious coatings: Alternative anode materials for impressed current cathodic protection systems intended for reinforced concrete

AbstractIn this study, the functionality of self‐formulated carbon‐based conductive coatings (CBCCs) with incorporation of graphite as the anode in an impressed current cathodic protection system is studied. The anode materials are tested and evaluated for long‐term durability and performance by an accelerated durability test method. The results show that the functional time is highly dependent on the acceleration factor, and thus the charge passed through the material during testing, as well as the material composition. From the results, there are also indications that the addition of graphene into the CBCC matrix has a positive effect on the homogeneity of the material, but without any major influence on the conductivity and performance.

Voltage Impact on Oil Pipelines from High Voltage Underground Cables: Relocation of Overhead Lines at Kelanitissa

When a large-scale urban construction project requires the relocation of an electrical overhead transmission line, going underground becomes the only feasible solution. However, due consideration must be given to the interaction with underground steel pipelines already laid as the life of metallic pipelines is highly susceptible to corrosion when buried underground. Corrosion occurs because of an electrochemical reaction, with Impressed Current Cathodic protection, with an impressed negative dc voltage of the order of 850 mV, usually employed in many metal pipelines to mitigate the deterioration of the surface. This paper scrutinizes the impact of high voltage underground cables on the cathodic protection of buried metal pipelines. The induced voltage due to the addition of high voltage underground cables crossing the pipelines perpendicularly has been analysed using Ansys Maxwell’s electromagnetic software using actual dimensions and parameters. The introduction of two 220 kV underground cables from Biyagama - Kelanitissa line and two 132 kV underground cable circuits from Kelanitissa - Kolonnawa running perpendicular to six underground petroleum carrying steel pipelines has been investigated to study its influence on existing impressed current cathodic protection. The study has shown that the maximum induced voltage is less than 1.5 mV which has no adverse effect on any existing impressed current cathodic protection. The high voltage cables have been in fact installed and no adverse effects have been detected.

Factors Governing the Failure of Subsea Critical Connector Bolts

Impressed current cathodic protection (ICCP) systems are commonly used to shield offshore drilling rigs, pipelines, and subsea equipment in the oil and gas industry. In underwater service conditions, water temperature, salinity and velocity play a major role in the longevity of subsea applications. Interactions between the preceding factors can induce catastrophic failure to critical systems while the underlying cause is unclear. This paper proposes an approach for elucidating the corrosion process accompanying underwater applications. The service conditions of underwater application are simulated in a multidisciplinary system that records various parameters such as water temperature, reference-electrode potential, and electric current at five-minute intervals during the 21 d of the experiment. This novel, experimental, and inexpensive ICCP system was developed on an “Arduino” microcontroller and applied to an actual ASTM A193 B7 bolt tightened on an ASTM A105 flange at different torque levels. Experimental results indicate a direct relationship between the water day-night temperature profile and the cathodic protection performance. Specifically, the ICCP performance declines with increasing temperature. When the ICCP system was activated, gas bubbles are generated on the metal surface. Presumably these bubbles could induce hydrogen embrittlement cracks which were observed in scanning electron microscope images of the bolt cross-sections.

Analysis of hydrogen embrittlement and applied potential of 1670, 1770, and 1860 MPa ultrahigh-strength steel wire for impressed current cathodic protection on cables and hangers

The hydrogen embrittlement and applied cathodic potential of three ultrahigh-strength steel wires were analyzed. Results show that in the simulated rainfall environment, the suitable protection potential range for 1670 and 1770 MPa wires is from the corrosion potential to −1150 mVSCE, and to −1050 mVSCE for 1860 MPa wire; the protection efficiency can reach 22% compared with unprotected steel wire at the recommended potential. The hydrogen diffusivity decreases with the strength, and are 0.636 × 10−6, 0.577 × 10−6 and 0.409 × 10−6 cm2ꞏs−1 for the three steel wires. The 1860 MPa wire has the highest HE susceptibility compared to the 1670 and 1770 MPa wires.

Investigation of residual protection of a 55 years old marine structure after 20 years subject to impressed current cathodic protection

It has been reported that structures to which impressed current cathodic protection (ICCP) has been applied for a long period have displayed evidence of residual protection when ICCP has been halted, ranging from several days up to significantly longer periods. To study this phenomenon this paper reports the de-activation of a 20 years old ICCP system installed on a 55 years old wharf structure. The ICCP was de-activated for 84 days and the reinforcing steel potentials at locations on the front pile cap and front wall were monitored via the existing installed reference electrodes (RE). The results showed that all the RE installed in the structure initially demonstrated a positive shift in potential, with 61% maintaining a positive trend over the entire trial period.

The Accuracy and Efficiency of a Single-Level Fast Multipole Boundary Element Model for Analyzing Cathodic Protection of Large Pipeline Networks

A single-level fast multipole boundary element method was developed for analyzing cathodic protection (CP) systems of large pipeline networks. This method was obtained by embedding far-field approximation within the traditional single-level fast multipole method. The far-field approximation was used for computing the coefficients for far elements within adjacent cells and determining the moments of the elements within far cells. This approximation reduced the difficulty of the procedures and programming leading to a significant decrease in computational time. The Newton-Raphson method and generalized minimal residual method were combined based on the proposed method to solve the nonlinear boundary conditions due to the polarization curve. Several CP problems were considered to verify and evaluate the method. The calculated potentials of this method were in good agreement with the conventional boundary element method, which was achieved by using pipe elements and quadrilateral elements to mesh the surfaces. Finally, the impressed current CP systems of a large network (more than 100,000 elements) and a complex urban gas network were investigated. The results indicated the capability, efficiency, and precision of the present method for solving large and complicated problems on a common desktop computer.

Effect of seawater pH variation on the growth of calcareous deposits and its effect on an impressed current cathodic protection system

Effect of seawater pH variation on the growth of calcareous deposits and its effect on an impressed current cathodic protection system

Electrochemical Performance of Concrete Conductive Anode Paint Used as an Impressed Current Anode Material

The impressed current cathodic protection (ICCP) technique is a widely accepted technique to control corrosion of steel in reinforced concrete structures exposed to a high chloride environment. With the growing applicability of the technique, this research focused on developing a new anode material for the system. The author’s previous zinc-rich paint (ZRP) anode is further modified to improve its properties and its performance to be suitable for ICCP. The new concrete conductive anode paint (CAP) was evaluated for various concrete elements with varying steel: concrete ratios. Results showed that concrete CAP possesses excellent electrical conductivity as the anode for the ICCP system irrespective of specimen size. Compared with other available commercial anode paint materials and ZRP anode, concrete CAP is more promising as an ICCP anode material and satisfies the required polarization requirement. Polarization performance showed anode is capable to protect reinforced concrete structure with varied steel: concrete or steel: anode ratio. With an anode current density of 20 mA/m2, the service life was evaluated as 45 years.