Cathodic Protection Of Steel Research Articles

Long term performance of reference electrodes for cathodic protection of steel in concrete

This paper will report on long term behaviour of potential sensors used in cathodic protection of steel reinforcement in concrete. Cathodic protection (CP) systems, both impressed current CP (ICCP) and galvanic CP (GCP), need regular testing to establish the quality of protection. In addition, ICCP may require adjustment of output voltage or current. Various types of potential sensors have been used in relatively large numbers, comprised of true reference electrodes (RE) based on silver/silver chloride or Mn/MnO2 and decay probes (DP) based on a.o. activated titanium. Failures may occur due to loss of contact, drying out or cable defects. Test methods for potential sensors are discussed. Monitoring of about one hundred CP systems with several thousands of potential sensors over more than ten years allows to analyse their performance and failures. It appears that limited numbers of potential sensors fail over time, but in some cases an insufficient number of working potential sensors are left to properly monitor a CP system or zone. It is recommended to install more potential sensors than strictly needed in order to allow for failures and to maintain testability and save the high cost of installing new potential sensors later.

Electrochemical Activation of Nickel Oxide Incorporated Aluminum-Zinc Alloy Matrix as an Efficient Sacrificial Anode in Marine Environments

For cathodic protection of steel, the aluminium-zinc alloy sacrificial anodes incorporated with nickel oxide nanoparticles were fabricated. The metallurgical properties of Al-Zn sacrificial anodes enhanced substantially through the infiltration and uniform dispersion of nickel oxide nanoparticles into an Al-Zn matrix. Such effective and uniform presence of nano nickel oxide inside the interior mass of the anodes was characterized by electrochemical techniques. The anodes showed considerably low polarization, steady and high active open circuit potential and substantially decreased self-corrosion during galvanic exposure for prolonged periods. The presence of nickel oxide nanoparticles in the anode matrix caused effective destruction of the passive aluminia film, which facilitated enrichment of galvanic performance of the anode. The anode had high resistance against biofouling also.

Cathodic protection of precast, prestressed multistory car park slabs, using a surface applied galvanic zinc layer anode

A surface applied galvanic Zinc Layer Anode (ZLA) system was installed on a multistory carpark structure to provide cathodic protection to the soffits of the prestressed hollow concrete slabs, which were suffering from chloride induced corrosion deterioration. This paper evaluates the cathodic protection system performance against the international standard for Cathodic Protection of Steel in Concrete, ISO 12696 [13], 17 months after commissioning. A surface applied galvanic Zinc Layer Anode was selected to provide cathodic protection, as this offered a low risk of exceeding the hydrogen embrittlement potential and provided a unique application approach, which was compatible with the hollow slab construction. During the pilot phase, a total of 40 m2 of ZLA was applied into two anode zones and monitored for a month, to prove concept and system performance. Following the pilot phase the remainder of the cathodic protection works were completed, extending to a total concrete area of 320 m2. The installed system was provided with embedded reference electrodes and wired to enable full performance evaluation as per the requirements of ISO 12696. Three battery powered web-based monitoring devices were used for remote system monitoring and performance assessment. The initial performance data following 17 months of operation, identified that all 12 reference electrodes installed across the 6 anode zones all met the 100mV depolarization criteria within a 24-hour period, as per the requirements of clause 8.6b of ISO 12696. The anode to cathode current was also recorded continuously over this operational period and used to evaluate environmental effects and predicted actual anode service life.

Use of a CFRP reinforcement anode for the cathodic protection of an iconic building

This paper reports the use of a new impressed anode for the reinforcement and the cathodic protection of steel reinforced rebars in concrete beams and columns of a French historical monument. It deals with the application of a dual effect of CFRP reinforcement. The application of a DC current on a carbon fiber-reinforced-polymer used both as a structural reinforcement and as a surface anode, allowed to polarize the steel in concrete. It was then possible to combine the strengthening function with the development of a multifunctional composite allowing protecting of steel rebar from corrosion but also the monitoring of repairing function versus time. The key to success in the development of this surface anode-reinforcement was the possibility of obtaining uniform distribution of current. This innovative technique was applied to the conservation of the reinforced concrete beams and columns of an iconic building of the north of France: the Belfry of Le Touquet’s city hall

A Historical Review of Impressed Current Cathodic Protection of Steel in Concrete

This paper reviews the history of the development of impressed current cathodic protection of atmospherically exposed reinforced concrete from the first trials in 1959 on bridges to recently installed systems on a wide range of structures around the world. The paper covers the research efforts, anode developments, control systems and monitoring sensors which are reviewed and their evolution explained. The research into the potential and actual side effects of cathodic protection currents in concrete are summarised. The development of standards and guidance on impressed current cathodic protection is also reviewed.

Study of the effect of tensile stresses on hydrogen absorption upon cathodic protection of steel in sea water

When using cathodic protection of steel in sea water, hydrogen can be accumulated on the cathode surface and penetrate deep into the metal. This rather dangerous phenomenon of hydrogen corrosion can lead to hydrogen embrittlement, i.e., to destruction of the metal. We present the results of studying the impact of the temperature and external tensile stresses on the hydrogenation of cathodically protected steel in calm and mobile Baltic sea water. Dependence of the inhibitory hydrogenation on the temperature and applied load under the action of benzenesulfapyridine chloride as an inhibitor was analyzed. An MIP-102 machine (wire samples) and special equipment (half-ring and plate lamellar samples) were used to provide smooth control of the applied load set by the deflection and controlled by dynamometers (lamellar samples were tested under constant deformation). When studying the effect of temperature on steel hydrogenation, the working cell was thermostatically controlled. The wire and plate samples were polarized for 96 h, and half-ring samples for 1 h. The potential was measured with respect to the silver chloride reference electrode. The layered distribution of absorbed hydrogen in the metal was determined using anodic dissolution. It is shown that external tensile stresses increase the hydrogen content in the surface layers of steel. Hydrogen absorbed by a metal changes the potential of the steel surface (the more absorbed hydrogen, the stronger change). It is also shown that hydrogen is absorbed by the metal more actively in moving seawater than in calm water, and an increase in the load contributes to an increase in hydrogen content in the metal both in calm and mobile seawater. However, the load did not affect the hydrogen absorption with the inhibitor present, thus providing reduction of the hydrogen content in the metal under loading.

Cathodic Protection of Steel from Corrosion in Reinforced Concrete Buildings using Sacrificial Surface Anodes of Zinc

Corrosion of steel in reinforced cement concrete is one of the major factor for deterioration of RCC structures. The corrosion of steel leads to failure or needs demolition of structures. Cathodic protection technology is well proven for corrosion protection of steel and in 2020 this technology will complete its 200 years of existence. For RCC buildings cathodic protection technology is not common due to several reasons. The lack of awareness in public about the fact that maintenance is only cosmetic repair and it does not ensure the protection of steel from corrosion. The sacrificial anode CP system is well suited for buildings since the requirement of anode material will always be less in case of buildings. To make it popular a new system of SACP is developed and it is named as Sacrificial Surface Anode Cathodic Protection (SSACP) system. The device is designed as external, it is easy in installation, replacement and monitoring. It is reliable, economical and does not damage the aesthetic appearance of building. The present research is about onsite corrosion prevention of steel using Sacrificial Surface Anode. For evaluation of performance a number of SSA are installed in one of the multi-story buildings in Surat city about 18 km from sea shore. This includes the working of SSA which depends upon the resistivity and moisture content of concrete cover to reinforcement.

Electrochemical behavior of zinc layer anodes used for galvanic protection of steel in reinforced concrete

Steel corrosion is the most common reason for the premature deterioration of reinforced concrete structures. Consequently, cathodic protection of steel in concrete has been substantially developed during the past two decades. In particular, galvanic protection consists in generating a natural macrocell corrosion system in which a sacrificial metallic anode (zinc, typically) is involved to apply a cathodic polarization to the corroding steel layout, in order to mitigate or annihilate the corrosion kinetics. Whether the general principle of cathodic protection is not questionable, the global design process can be significantly improved by increasing the knowledge on electrochemical behaviours of the different components of the protecting system. Regarding zinc anodes in concrete, the literature is very scarce. The time evolution of such systems is also not rigorously addressed, aging effects are systematically ignored and zinc anodes are usually considered as non-polarizable and inert over time. In this paper, the polarization response of a zinc layer anode (ZLA) in concrete electrolyte and its time evolution are studied. The results show a rapid evolution of the ZLA behavior, once the protecting system is connected to steel reinforcements. Moreover, the characterization of ZLA provided relevant electrochemical properties for the numerical design of galvanic protection systems.

Cathodic protection of steel in concrete – experience and overview of 30 years application

This paper presents an overview of 30 years' experience with cathodic protection of steel in concrete in The Netherlands. Principles and practical aspects of CP and its design and installation are presented. Three phases have passed from the late 1980s until present: pioneering, development and maturity. In the first period CP was mainly applied to precast elements corroding due to mixedin chlorides. The parties involved worked together to draw up a Technical Guideline. In the second period, application to bridges came up, including post-tensioned structures, which was then innovative. Furthermore, galvanic anode systems were introduced. In the third period, CP became a fully accepted method of securing durability and safety. Renewed collaboration led to a database that allowed analysis of various aspects of CP system working life, including shortcomings in early systems. Major successes and lessons learned will be presented. Technical and non-technical developments are highlighted and some recent innovative CP components and systems are discussed.

Corrosion of Aluminum Alloy Used as Sacrificial Anode for Steel Embedded Concrete Transmission Tower in Brackish Mud

This paper presents the cathodic protection of steel embedded concrete of aluminum based alloy in brackish mud. In this experiment, aluminum based alloys containing 5% zinc, 2% magnesium, and 0.5-2% stannum were fabricated. These elements were added because they produce heat treatable alloys, improved anti friction characteristics, fluidibility, and contain highest strengthening effect on aluminum alloys. These alloys were tested as sacrificial cathodic protection for the standard steel embedded concrete exposed to sea water and brackish mud. Surface morphology of the samples after subjected to corrosion was investigated through scanning electron microscopy (SEM) and anode capacity test (efficiency test). The results revealed that sample with the composition of 95.6% of aluminum, 3.83% of zinc, and 0.19% of stannum showed the best performance hence it was selected for cathodic protection in brackish mud.

The influence of the internal microbiome on the materials used for construction of the transmission natural gas pipelines in the Lodz Province

This paper presents investigation results of the influence of gas microbes on the biocorrosion rate of the materials used for gas pipelines construction in the Lodz Province. Samples of two types of carbon steel and cast iron were stored in the laboratory pipeline model reflecting the real conditions of working natural gas pipelines were. In the next step the influence of cathodic protection with parameters recommended for protection of underground structures was tested. Analyses of biological corrosion products generated on the test surface were carried out using a scanning electron microscope with an X-ray analyzer. The level of ATP was measured to confirm presence of the adsorbed microorganisms on the observed structures. Corrosion rates were determined by gravimetric methods. In the course of the study it was revealed that the rate of biocorrosion of steel is lower than that for cast iron. Our results also proved that the weight corrosion rate depends on the number of adhered microorganisms. In addition, it has been found that application of the carbon steel cathodic protection decreases its weight corrosion rate. The information obtained will help to increase the knowledge on the rate of biological corrosion causing losses/pits inside gas pipline.

Book review

Cathodic Protection of Steel in Concrete and Masonry, second edition

流電陽極方式電気防食によるコンクリート中鉄筋の防食効果に関する検討

塩化物イオン濃度が異なる鉄筋コンクリート試験体に対してアルミニウム系流電陽極方式の電気防食法を適用し，通電電流が変化する要因の特定と電気防食時の鉄筋の腐食速度および鉄筋の自然腐食状態の改善効果を検討した．その結果，通電電流の低減は，経時的な鉄筋のカソード分極抵抗の増加とコンクリート抵抗の増加により生じることが考えられた．試験終了時には，初期に比べて鉄筋の自然腐食速度が低下した．また，電気防食時の鉄筋の腐食速度は，不動態保持電流密度に相当することが考えられた．

Zinc-free varnishes and zinc-rich paints modified with ionic liquids

The corrosion protection of a steel substrate using zinc-rich epoxy–alkyd paints (ZRPs) modified with either 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6) or 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyrrTFSI) has been investigated. Additionally, the influence of ionic liquids (ILs) on the corrosion process of uncoated steel and zinc as well as on electrical features of zinc-free varnishes has been evaluated. The pyrrolidinium IL significantly reduces the corrosion rates of steel and zinc but the ZRPs with HMIMPF6 offer better cathodic protection of steel than unmodified ZRP and ZRPs with BMPyrrTFSI. The electrical conductivity of IL is not critical for the protective features of ZRP.

Influence of irregularities in the electrolyte on the cathodic protection of steel: A numerical and experimental study

This paper shows how the last algebraic matricial form can be obtained when the finite element method is used to approximate the potential distribution of a cathodic protection system that includes low conductivity irregularities in the electrolyte away from, close to and directly on the cathode. In order to study the influence of the resistivity of these irregularities on the possibilities of steel protection, five conductivities were analysed. The numerical results, validated with COMSOL® Multiphysics, show the importance of considering irregularities in the domain in order to prevent systems from becoming unprotected. The experimental data agrees with the theoretical data.

Effect of interphase interaction within zinc-filled composite coating on the potential of the cathodic protection of steel

The potential of cathodic protection of steel with composite coatings based on polystyrene (PS) filled by highly dispersed powders of zinc (Zn) of different forms and dispersivities is investigated. The potential for all PS/Zn systems with a low content of filler is shown to be less than for pure metal; as some critical value (the percolation threshold) is reached, the negative values of potential increase abruptly and become higher in absolute value than the potential of pure metal. The threshold zinc contents are found to depend on the particle shape and rise from 9 to 30 vol% upon transitioning from spear-shaped to spherical particles. The electrochemical protection properties of a composite coating are correlate with the enthalpy of mixing of filled composites. The enthalpy of mixing in regions of low filling is shown to be negative, indicating strong interphase interaction; that in regions of high filling is positive. The positive enthalpy of mixing corresponds to compositions that generate the potential of cathodic protection. It is found that an increase in the concentration range of positive values of a composition’s enthalpy of mixing occurs symbatically with a decrease in the threshold concentration of metallic zinc within the composition. We conclude that cathodic protection by zinc-filled polymeric composites is due to weak interphase interaction that results in the aggregation of particles of metallic zinc within a polymeric matrix and the appearance of an infinite cluster. In the case of PS/Zn compositions, it is shown that the infinite cluster appears at enthalpies of mixing greater than 0.6 J/g of the composition.

Hydrogen embrittlement behavior of HSLA line pipe steel under cathodic protection

This paper deals with hydrogen embrittlement (HE) under cathodic protection of steel used or recently proposed for buried pipelines of the oil and gas industry. High strength low alloy steel with different chemical composition, microstructure and ultimate tensile strength ranging between 530 and 860 MPa were considered to compare new steel with traditional grades. Their behavior was assessed through constant load tests, fracture mechanics tests on modified wedge-opening load specimens, slow strain rate tensile tests and interrupted slow strain rate tensile tests in solutions simulating soil moisture and sea water, at room temperature and cathodic potentials between -2 and -0.8 V vs. saturated calomel electrode reference. All the steel was found immune under static load and HE phenomena were observed only during slow strain rate tests at potentials more negative than a critical value, depending on steel susceptibility and strain rate. Quenched and tempered steel with high tempered martensite and very fine precipitation distribution showed better behavior than the rolled steels with banded microstructure, exhibiting the highest HE resistance. The resistance of steel characterized by banded microstructures increased with ultimate tensile strength until ∼700 MPa and then decreased. The increase of ultimate tensile strength occurred by changing the steel microstructure, from hot rolling with coarse ferrite/pearlite to fine ferrite/pearlite microstructure, and very fine acicular ferrite, yields the resistance of steel to HE. A further increase of ultimate tensile strength related to untempered martensite inside the acicular ferrite based microstructure produces a worsening of resistance.

Investigations on the chloride migration in consequence of cathodic polarisation

AbstractAt the Institute for Building Materials Research (ibac) in Aachen and the Federal Institute for Materials Research and Testing (BAM) in Berlin a joint research project is currently running with the aim to develop a numerical model which describes cathodic protection (CP) of reinforced concrete. Special project focus is the CP of the rear reinforcement layer. The resulting model shall include the impact of chemical alterations at the steel surface and within the adjacent concrete on the polarisation behaviour of reinforcement, which are induced by long‐term application of CP. The investigations presented in this paper aim to clarify open aspects on the migration of chloride ions due to small electric fields as applied in CP of steel in reinforced concrete structures. A comparatively new method, laser induced breakdown spectroscopy (LIBS), was applied in order to determine chloride concentration profiles on laboratory specimens as one of several model parameters for a mathematical description of CP of the rear reinforcement of reinforced concrete structures. The paper concerns migration tests using non‐saturated specimens under laboratory conditions at constant voltage and the application of the experimental parameters on FEM‐calculations. The presented results suggest the conclusion that even comparably small electric fields, as applied in CP of steel in concrete, may lead to significant and sustainable reduction in chloride concentration at the surface of the reinforcement.

Role of sulphate ions on the formation of calcareous deposits on steel in artificial seawater; the formation of Green Rust compounds during cathodic protection

Cathodic protection of steel in seawater could be optimized by taking into account the calcareous deposits forming on the steel surface. The aim of this work was to study the influence of sulphate ions on the kinetics and mechanisms of formation of these deposits. The experiments were performed at 20 °C, with an applied potential of −1.0 V/saturated calomel electrode (SCE), in artificial seawater-like solutions with various SO 4 2− concentrations. The deposition was monitored by chronoamperometry and electrochemical impedance spectroscopy (EIS). Micro-Raman analyses were performed in situ in a specific electrochemical cell to identify the solids forming on the steel surface. It could be demonstrated that sulphate ions had an important effect on the formation of both Ca(II)- and Mg(II)-containing phases. In the solution enriched with sulphate ions, the deposition of CaCO 3 was almost totally inhibited. Experiments performed in Ca 2+-free solutions demonstrated that the Mg-based deposit was, in contrast, favoured by the increase of the sulphate concentration. In situ Raman spectra of the solid forming at the early stages of the cathodic protection proved to be characteristic of Green Rusts (GRs). This compound was favoured by the presence of Ca 2+ and/or Mg 2+ cations, and is more likely a GR-like M(II)-Fe(III) hydroxysulphate, with M = Fe, Mg and Ca.

A Study on Cathodic Protection of Carbon Steel in Flowing Tap Water : Effect of Corrosion History on the Cathodic Protection of Steel

A Study on Cathodic Protection of Carbon Steel in Flowing Tap Water : Effect of Corrosion History on the Cathodic Protection of Steel