Cathodic Protection Method Research Articles

Design and analysis of the cathodic protection system of oil and gas pipelines, using distributed equivalent circuit model

Cathodic protection (CP) method is widely used in the oil and gas industry in order to prevent (or reduce) rust and corrosion of structures and metal pipelines or their associated cost. To guarantee a more effective CP system, an applicable design for the under protected structures is required. The conventional models recommended by the designers are based on the equivalent circuit of the overall CP system, which are lumped model and may be useful for the compact systems like integrated industrial plants, where oil and gas pipelines are installed in kilometers. Since such a lumped model leads to inaccurate results, this study aims at proposing a new distributed model to design a cathodic protection system for oil and gas transmission pipelines, which is extendable and can be useable in other structures. The main difference between the proposed model and the conventional approach is the use of actual measured soil resistance throughout the structure instead of using a fixed mean value. The effectiveness of the proposed model has been demonstrated by analytical analysis and computer-based simulations. The proposed method shows a significant superiority over the conventional lumped models when variation of the soil resistance through the structure is high. Hence, the application of the devised method in design of a CP system of the pipelines improves the quality of the protection. The distributed equivalent circuit model with its distributed parameters is utilized to design and analyze the performance of a real case i.e., the CP protection system of a 20-km transmission pipeline with soil-measured data. To calculate the performance of the designed CP system, the results are compared with those of the conventional model.

Effect of Pulse Frequencies on Low Carbon Steel in 3.5 wt% NaCl Solution under Zero Charge Corrosion Protection

Zero charge corrosion protection (ZCCP) is an alternative to the existing cathodic protection methods. It applies a current/voltage pulse with a certain particular frequency to attain a potential of zero charge (Epzc) on the electrode-electrolyte interface. A study on the pulse frequencies of ZCCP system on low-carbon steel in 3.5 % NaCl Na solution was carried out for 14 days. The pulse frequencies are varied from 4, 20, 50 and 100 Hz. The ability of these frequencies in protecting samples is determined by means of corrosion rate based on weight loss analysis and surface morphology. Experimental observations indicate that low carbon steel corrosion protection is strongly influenced by changes in pulse frequency. Corrosion rates were found to gradually decrease as pulse frequency increased from 4, 20 to 50 Hz, nevertheless at higher frequencies (100 Hz), corrosion protection was observed to be less effective where the corrosion rate dramatically grew up. The surface morphology of the steel surface is smooth and protected at a pulse frequency of 50 Hz. This indicates that the current / voltage pulse of ZCCP system only requires 50 Hz which is equivalent to a standard AC power frequency applied in most countries including Malaysia.

Pipeline Corrosion Protection Simulation of Cathodic Protection Method Againts Electrochemical Potential Distribution

Corrosion protection is very necessary for all steel or other types of metal, especially in buried pipes (underground construction). Direct contact between pipe materials (Carbon steel) can accelerate the corrosion rate. This is the case with the 20 inch pipe project working on the pipe installation. Initially to prevent this type of corrosion was done cathodic protection, but the result of examination was proven that there was a leakage of the potential distribution protection to the ground. Therefore it is necessary to do a distribution protection simulation to get how many anodes (magnesium package) to meet protection needs. The anode distance simulation results on the distribution of potential are carried out with the following variations: distance of every 45 meters, distance of every 30 meters, distance of every 20 meters, and distance of anodes every 15 meters. Based on the simulation results it is found that the anode distance cannot meet the minimum protection (-850milli volt) except at a distance of 15 meters. Installation of anodes at a distance of 15 meters with each pair of distance of 4.9 meters proved that the simulation results have met the minimum potential for corrosion protection. So that it can be used as a reference for installation of anode spacing for pipe corrosion protection.

Effect of cathodic protection methods on ferrous engineering materials under corrosive wear conditions

ABSTRACT Cathodic protection prolongs the service life of fluid transport and offshore engineering components by suppressing corrosion. This study assesses the effect of two cathodic protection methods, such as impressed current cathodic protection (ICCP) and sacrificial anode cathodic protection (SACP), on three ferrous-based materials under laboratory-controlled corrosive wear conditions. The SACP was as effective as ICCP on the protection of the low alloy steel and white chromium cast iron under both solid and solid-free corrosive wear conditions. Under solid–liquid impingement, significant reductions in the material loss were also observed in both the direct impingement zone and the outer area (oblique angle of attack). This demonstrates the substantial impact of cathodic protection systems that are exposed to erosion–corrosion dominated environments.

A New Method of Edge Crack Suppression in the Rolling Process of Magnesium Alloy Sheet and Study on the Method of Cathodic Protection

A new method is proposed to solve edge cracking and corrosion in rolling process of the magnesium alloy plate. Usually in the process, the edge cracking is caused by the great temperature difference between the edge and the center of the alloy plate and the corrosion is by water in air. The method uses hot air wrapped around the plate to perfectly prevent edge cracking and corrosion. The method also includes cathodic protection for the magnesium alloy based on electrochemistry. The suppression of cathodic protection on the chemical activity of the magnesium alloy was studied. The experiment shows that the new method of edge heating with hot air wrapping is effective to prevent edge cracking and corrosion. Also, the cathodic protection can effectively suppress the chemical activity of the magnesium alloy and improve the surface quality in the rolling process of the magnesium plate, which provides a new concept in rolling process of the magnesium alloy.

Investigation of the impressed current cathodic protection method for the cable parallel wires in the rainwater electrolyte based on acoustic emission method

The corrosion durability of bridge cables in operation is prominent. This study proposes an active protection method to apply impressed current cathodic protection (ICCP) to bridge cable parallel wires. The weight loss method, scanning electron microscopy, electrochemical test, and acoustic emission (AE) signal characteristic analysis were used to study the test method for electrochemical corrosion protection of cable parallel wires using rainwater conduction. Results show that cable wires are corroded on the surface and inside, whereas the cable wires with ICCP show different changes. The cable wires are effectively protected in the environment where a sodium chloride solution is used to simulate rainfall. In the AE test of the cable wires after corrosion using a signal generator, the main frequency of the AE signal gradually increases with the increase in corrosion degree. The high corrosion degree of the cable wires induces dispersion. The characteristics of AE signal can reflect the corrosion degree of the cable wires, and ICCP can decrease the corrosion rate of the cable wires.

Development of Sacrificial Anode Usable in High Specific Resistivity Solution by Parameter of Addition of NaCl

A sacrificial anode cathodic protection method has been widely used in the steel pile by galvanic current by potential difference between sacrificial anode and corrosive structural steel. And, the sacrificial anode cathodic protection method have generally merits compared to impressed current method because it can be applied to everywhere which is not connected with electricity. However, when the steel piles of the pier are submerged in low conductivity solution mixed with fresh water and sea water, the structural steel piles mentioned above have not been protected occasionally perfectively due to decreasing of galvanic current caused by deposited with oxide film on the surface of anode. In this study, five types of samples which are added with NaCl(g) to Zn anode were prepared with ratio of NaCl(g)/Zn(g)x100(%). And galvanic currents, surface morphologies characteristics of these samples was investigated using electrochemical methods such as polarization curves, galvanic current and analysis of surface morphologies before and after reduction weight ratio test in order to evaluate the effect of addition of NaCl(g) affecting to quality of zinc anode. The 2.6 % sample added with NaCl(5g) showed the highest value of galvanic current density in 0.8% NaCl solution, however, the highest reduction weight ratio was also observed at the 2.6% sample. Therefore, it is considered that the higher galvanic current density, the higher reduction weight ratio, that is, the life of sacrificial anode is shorted with increasing of galvanic current. Moreover, all samples added with NaCl(g) to Zn sacrificial anode indicated higher galvanic current density compared to the sample with no addition of NaCl(g) in low conductivity solution. Eventually, it is supposed that the galvanic current can be increased with addition of NaCl(g) to Zn sacrificial anode in low conductivity solution.

Study of Protected Current for Stainless Steel and Carbon Steel Cathode from Rust Attack to Determining Optimum Flow of Electricity

Rust protection in a construction can be done by several methods such as the use of organic or inorganic layers of protection, anodic protection, and cathodic protection method. Cathodic protection consists of protection by using sacrificial anode as a producer of a protected current and using a protection current generated by an external power supply continuously. In a water-immersed construction commonly used sacrificial anode as a protection against rust in the construction, such as water tank. A sacrificial anode (rod, usually Magnesium or Zinc) is inserted in the construction. When submerged, the anode will be submerged. Water serves as an electrolyte solution. By connecting the sacrificial anode with the construction, a cathode anode system is formed. The anode releases the electrons and undergoes an oxidation reaction, while the cathode undergoes a reduction reaction. By achieving an equilibrium between the oxidation and reduction reactions, the construction is protected from rust. Considering the above, then made the system of protection against rust that is more practical by using the current protection method. The difference with the sacrificial anode method is the use of an external power supply to produce a current (direct current) that is passed through an inert anode such as aluminum, stainless steel or graphite, so no anode replacement is required as long as the tank is used. Using a simple circuit, the amount of electric current flowed can be adjusted according to the dimensions of the tank. Electric current used is also relatively small so it is safe for users. To study the above system made a model use stainless steel and carbon steel material to be able to determine the optimal protection current.

Determination of the auxiliary anode position via finite element method in impressed current cathodic protection

Purpose It is a challenge in the design to determine the feasible anode position and the supply current when the hull is protected by the impressed current cathodic protection method. It is difficult to obtain these parameters through traditional experimental methods due to the huge hull surface area and geometric complexity. This study aims to solve the problem by finite element method. Design/methodology/approach First, a great number of experiments need to be conducted; second, experiments are empirical; finally, there exist measurement errors, etc. All these factors make the experimental results less reliable. The application of the finite element method, combined with other technologies, is expected to overcome these deficiencies. In this paper, the combined Matlab and Comsol method was used to calculate various anode positions and corresponding protection areas with a series of input current conditions. The calculation is implemented via the script in Matlab. Findings As a result, the best design can be obtained. The results show that the method provided in this paper can replace the experiment to a certain extent, save human and material resources and reduce the design time. The method also can be applied to other similar fields, having a good universality. Originality/value This optimization method can be extended to other areas of relevant production and research, having a good universality.

A Study on Galvanic Current Variation of Zn Sacrificial Anode Made by Including of Additive in Solutions with Various Conductivities

There have been two cathodic protection methods to inhibit corrosion of the structural steel piles which are being immerged under seawater, or to control corrosion of a hull part of the ship exposed to sea water. One of them is a sacrificial anode cathodic protection method that the steel pile can be protected with galvanic current by potential difference between sacrificial anode and corrosive structural steel. And, the sacrificial anode cathodic protection method have generally merits compared to impressed current method because it can be easily applied to everywhere which is not connected with electricity. However, when the steel piles are being submerged in low conductivity solution mixed with fresh water and sea water, the structural steel piles mentioned above have not been protected occasionally perfectively due to decreasing of galvanic current of zinc anode caused by deposited with oxide film on the surface of anode. In this study, four types of zinc anodes samples which are included with three types of additives such as NaCl, KCl, and ZnCl2were prepared, and galvanic currents, the polarization characteristics of these anodes was investigated using electrochemical methods such as polarization curves, impedance, cyclic voltammogtam and galvanic current in order to evaluate the effect of additive affecting to quality of zinc anode. The sample added with NaCl indicated the highest value of galvanic current density compared to other samples in the case of lower and higher conductivity solutions such as 0.32 and 2.97mS respectively, and the sample added with KCl revealed the smallest galvanic current density in middle value of conductivities such as 1.53 and 2.27 mS. Moreover, Zn sample no added with additive exhibited the smallest value of galvanic current density in the lowest conductivities such as 0.32 and 0.98 mS. Therefore, it is considered that the galvanic current of the sacrificial anode can be increased by adding of additive when the anode is submerged in low conductivity solution mixed with fresh water and sea water.

Numerical approach of impressed potential on buried pipelines near high‐voltage DC grounding electrodes

In developed area, there is not only dense electric power grid, but also dense gas pipelines. In this situation, the DC current injected into the earth through the grounding electrodes of a high-voltage DC system would aggravate the corrosion and even destroy the protection devices of the pipelines. In this study, a numerical approach is put forward to simulate the potential distribution in gas pipeline, which is regarded as long grounding system with insulating coating on the grounding conductor. The main cathodic protection methods for the pipeline are also modelled. The approach is validated by the experiment on a reduced-scale model. With this approach, the effectiveness of the measures to reduce the electrode potential distribution along the pipelines is analysed.

Optimization of the Cathodic Protection Design in Consideration of the Temperature Variation for Offshore Structures

The temperature effect on the current density which closely related to cathodic protection (CP) design was examined using electrochemical tests. A case study of an optimized CP design for the floating production storage and offloading using a computational analysis tool was also performed. The electrochemical test results showed that the current density and the surface resistance of the specimen (EH36) at 28°C are lower and higher, respectively, compared with the 5°C condition; this phenomenon is the result of a calcareous deposit that was verified by scanning electron microscopy and energy dispersive x-ray spectroscopy surface analyses. The polarization curves which contained the effect of calcareous deposits according to the temperature were used as the computational analysis input data. The simulation results showed that the structure under the 5°C condition did not satisfy the CP criteria (−800 mVSCE to −1,050 mVSCE) at the bottom shell and the mooring chain. It had higher potential than −800 mVSCE. Although the structure at 28°C satisfied the protective potential range, it was sufficiently unstable for the prediction of the corrosion damage. To optimize and resolve the identified problems, the CP design was changed by CP methods, anodes quantities, and anodes distribution. Consequently, the structure at 5°C is sufficient for the satisfaction of the protective-potential criteria (< −800 mVSCE) at the bottom shell and the mooring chain. In the case of the structure at 28°C, a more-even potential distribution was achieved.

Experimental Study of Thermoelectric Generator as Electrical Source of Impressed Current Cathodic Protection for Ship Hull

Impressed Current Cathodic Protection (ICCP) is a method to protect metallic material such as ship hull from corrosion by using electric current. In this research, a prototype of thermoelectric generator is developed in order to supply the ICCP system. This thermoelectric generator is planned to utilize the exhaust gas from main engine of the ship. Method carried in this research is assembling the prototype of thermoelectric generator followed by conducted experiment to observe the potential energy of the prototype. After that, the required number of thermoelectric generator is calculated to supply the ICCP system to protect the ship from corrosion. The object in this research is live fish carrier “Wellboat” which has 396.08 m 2 wetted area. The required voltage and current to protect the ship from corrosion for three years are 16.67 Volt and 2.66 Ampere. Based on the experiment, a prototype of thermoelectric generator can generate 0.34 Ampere and 4.43 Volt, causing the need of 8 series and 4 parallels connection. It can be concluded that the corrosion rate on the ship hull can be decelerated by using impressed current cathodic protection method without needing additional cost or fuel consumption to produce electric energy.

Analysis and Simulation of the Factors Affecting the Impressed Current Cathodic Protection Potential of the Ship

At present, the ship will use the impressed current cathodic protection (ICCP) methods for hull corrosion protection. Protection potential is the core parameter of the ICCP method, so how to set the protection potential value will determine the anticorrosive effect of ship. Firstly, establish ship ICCP potential calculation model, and then discuss the impact of ICCP on potential and current density distribution of the factors in four aspects: distance between the anode and the body to be protected; corrosion resistivity variation influence on current distribution; anode arrangement and size influence on current distribution; coating influence on the potential and current distribution. Through simulation, it is confirmed that these factors affect the ICCP potential to provide a theoretical basis for the rational design of ICCP parameters.

해양환경 중 음극전류 프로세스에 의해 강판에 형성된 석회질 피막의 특성 분석

Cathodic protection is widely recognized as the most cost effective and technically appropriate corrosion prevention methodology for the port, offshore structures, ships. When applying the cathodic protection method to metal facilities in seawater, on the surface of the metal facilities a compound of calcium carbonate(<TEX>$CaCO_3$</TEX>) or magnesium hydroxide(<TEX>$Mg(OH)_2$</TEX>) films are formed by <TEX>$Ca^{2+}$</TEX> and <TEX>$Mg^{2+}$</TEX> ions among the many ionic components dissolving in the seawater. And calcareous deposit films such as <TEX>$CaCO_3$</TEX> and <TEX>$Mg(OH)_2$</TEX> etc. are formed by the surface of the steel product. These calcareous deposit film functions as a barrier against the corrosive environment, leading to a decrease in current demand. On the other hand, the general calcareous deposit film is a compound like ceramics. Therefore, there may be some problems such as weaker adhesive power and the longer time of film formation uniting with the base metal. In this study, we tried to determine and control the optimal condition through applying the principle of cathodic current process to form calcareous deposit film of uniform and compact on steel plate. The quantity of precipitates was analyzed, and both the morphology, component and crystal structure were analyzed as well through SEM, EDS and XRD. And based on the previous analysis, it was elucidated mechanism of calcareous deposit film formed in the sacrificial anode type (Al, Zn) and current density (1, 3, <TEX>$5A/m^2$</TEX>) conditions. In addition, the taping test was performed to evaluate the adhesion.

해수 내 아크 아연 용사코팅 층의 전기화학적 특성

In this paper, arc Zn thermal spray coating was carried out on the SS400 steel, and then various electrochemical characteristics and surface damage behavior of Zn thermal spray coating layer were analyzed. As the results, the potential of Zn thermal spray coating layer presented driving voltage above 300 mV compare to that of SS400 steel. The passivity characteristic in anodic polarization curve was not presented. It was adequate to as sacrificial anode material. In the surface damage after galvanostatic experiments, uniform corrosion tendency of Zn thermal spray coating layer was clearly observed with acceleration of the dissolution reaction. In conclusion, Zn thermal spray coating could be determined to represent the corrosion protection effect by stable sacrificial anodic cathodic protection method in seawater because it had sufficient driving voltage and uniform corrosion damage tendency for the SS400 steel.

The Photogenerated Cathodic Protection of Steel Using the Thin Layers of Photoactive Nanocomposite Fabricated By Electrophoretic Deposition

The photogenerated cathodic protection of steel can be achieved by a photoactive coating layer. It is recently attracting attention because it can overcome the limitations of the sacrificial cathodic protection method. In theory, it can provide permanent cathodic protection because it used energy from solar light rather than to consume itself to protect against corrosion of steel. In the present work, a novel nano-structured layer for the photogenerated cathodic protection was coated on steel using electrophoretic deposition (EPD). Through EPD, thin photoactive composite films can effectively be fabricated on conductive substrates using the colloidal suspension of functional nanoparticles with the simple application of an electrical field. Firstly, crystalline TiO2 nanoparticles were deposited on a steel substrate by the EPD process for the photo-generated cathodic protection. To improve the cathodic protection ability of the photo-stimulated layer, graphene nanoplatelets were incorporated into the TiO2 composite layer by the simultaneous co-deposition of graphene and TiO2 nanoparticles using EPD. Despite the superior cathodic protection afforded by a photo-stimulated TiO2 EPD layer, the coating only works when exposed to solar irradiation during the daytime. However, steel suffers from corrosion at all times. There have been many attempts to overcome this drawback. The incorporation of various photo-electron storing materials into the coating layer is the most promising strategy for maintaining the efficacy of the cathodic protection that is provided by TiO2 in the absence of sunlight. WO3 nanoparticles were used in this study to impart photo-generated cathodic protection to the EPD layer at all times. Moreover, the graphene was exploited as a barrier to protect steel from corrosion because it forms a better barrier to molecules. A graphene film was prepared on steel using EPD with a suspension of graphene oxide in water. When graphene was used as an underlying film for the organic coating, the corrosion resistance of the coated steel improved significantly.

Numerical analysis results of the cathodic protection for the underground steel pipe by anode installation method

This study aims to find out the best anode location for buried pipelines. Numerical simulation program known as CATPRO(Elsyca, Belgium) were used for confirming the best location of anodes and the effects of impressed current cathodic protection system. Applied conditions for numerical simulation were similar to on-site environmental conditions for optimal application of cathodic protection system. Used criterion of cathodic protection was NACE SP 0169, which describes that minimum requirement for cathodic protection is -850mV vs. CSE. Various layouts for anodes’ installation were applied, which were distance between anodes, anode installation location, and applied current. The areas where cathodic protection potential was lower than -850mV vs. CSE was limited up to 50m from anode installation locations. It was founded numerical analysis obtain cost-effective and efficient cathodic protection methods before design and application the impressed cathodic protection system to on-site environment.

A Study on Thermal Spraying Sacrificial Anode Applied in Concrete Structure Cathodic Protection

In this work, the thermal spraying sacrificial anode was investigated as reinforced concrete structure cathodic protection method. During our experiment, the performance of the thermal spraying sacrificial anode was studied using electrochemical method, metallographic microscopy method and simulation tests. And the results show that the thermal spraying sacrificial anodes are better than traditional sacrificial anodes. The method of thermal spraying applied in sacrificial anode field is successful, which solve the problem of insufficient driving initial potential of traditional sacrificial anode in the concrete structure.

Localised corrosion and cathodic protection of 17 4PH propeller shafts

Some 17 4PH propeller shafts showed severe localised corrosion after a long period of time in Ancona harbour. The shaft is concentrically mounted in an AISI 304 stern tube through two rubber bearings. Both 17 4PH and AISI 304 stainless steels were characterised by anodic polarisation in natural sea water, in order to obtain the necessary corrosion parameters for designing a suitable cathodic protection of the propeller system. The cathodic protection effectiveness was tested on a portion (about 1 m long) of this system. Two cathodic protection methods were tested: an impressed current cathodic protection at −0·3 V(SCE) and a galvanic cathodic protection. The tests were performed both in stagnant and in moving sea water and the results showed that these cathodic protection solutions were able to protect the propeller system; in particular some guidelines are suggested for both old and new ships.