Cathodic Protection Techniques Research Articles

Evaluation of the electrical properties of carbon electrodes developed with bio-material additions as a sacrificial anode in cathodic protection

The use of zinc and magnesium sacrificial anodes for the protection of steel structures in cathodic protection techniques have been widely accepted but longevity and environmental friendliness of these materials in service still needs to be improved. Thus, the need to continually develop anodes that can potentially serve the same purpose and/or better performance. This work is a feasibility study on the production of carbon electrodes for possible application as sacrificial anodes for the cathodic protection of mild steel. The main aim of this investigation is to develop an electrode from carbon-based materials with a view to producing anodes that can potentially replace zinc and magnesium electrodes for cathodic protection of low-carbon steel. The electrodes were developed using mixture of coal, charcoal, mill scale, wood dust and coal tar (binder) that were heated and compressed in a metal die. The current passing through the electrodes was measured with the resistance, resistivity and conductivity determined, including the current densities (Iρ) which gives an indication of the electrochemical behavior of the electrodes. Morphology of the electrodes were examined by optical microscope (OM) and scanning electron microscope (SEM) to assess the influence of porosities of the electrodes produced. Based on these findings, it was generally observed that the conductivity increases from 5.23E-4 S/m to 5.87E-3 S/m for 150 µm and 600 µm particle sizes, respectively. Generally, resistivity increases with an increase in the amount of wood dust in the carbon anodes developed. The carbon electrode of 600 µm particle size with the composition of 67 wt% coal, 5 wt% charcoal, 10 wt% coal tar, 10 wt% mill scale and 8 wt% wood dust had the best current density that could offer corrosion protection for mild steel.

On the Effect of Wave Signal Input via Zero Charge Corrosion Protection in 3.5% NaCl Solution

The technique of zero charge corrosion potential (ZCCP) acts as a new alternative of cathodic protection technique. A study of wave signal input in ZCCP technique was carried out on pure Mg steel in the 3.5% NaCl solution. This experiment was conducted within 48 hours. The wave signals input that had been used in this experiment are square, triangle, and sine wave. These waveforms have an impact on the corrosion protection of the ZCCP system. The effectiveness of waveform in ZCCP technique on corrosion protection was determined by morphology observation using stereomicroscope. It is found that, the lowest consumption of current density took placed at the square wave signal which is-0.99μA/cm2. Meanwhile, for triangle and sine wave, the current density recorded were-1.694μA/cm2 and-1.756μA/cm2, respectively. From the morphology observations, it is clearly seen that the square wave signal provides better corrosion protection as compared to the triangle and sine wave signal. There is no formation of localised corrosion detected on the Mg surface using square wave signal. This is because the % ‘ON’ and % ‘OFF’ in ZCCP system allows to set it to the desired value of potential.

Cathodic Protection Technique for Infrastructure Facilities

Cathodic Protection Technique for Infrastructure Facilities

Calcareous Deposits Formed Under Long‐Term In Situ Cathodic Protection Tests

AbstractThe calcareous deposits formed under commonly applied cathodic protection techniques on coated and uncoated carbon steel samples immersed in Guanabara Bay for 150 days, simulating ships and pipelines, were investigated. Potentials were monitored throughout the analysis, and deposits were examined by visual inspection, optical microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction. Beyond calcite, aragonite, and brucite, which are crystals commonly reported in laboratory tests or under confined space conditions, herein, also calcite‐II and calcite‐III were identified as intermediate crystalline structures. Furthermore, it was demonstrated that biological activity also plays an important role, forming calcareous tubular structures within the deposit.

Corrosion protection of steel members using an Al-Zn base sacrificial anode and fiber sheet in an atmospheric environment

A new cathodic protection technique for steel members in the atmospheric environment was developed in this study, Al-based alloy plate is a sacrificial anode, and fiber sheet was considered as electrolyte carrier. The reliabilities of components were clarified by comparing the material properties and electrochemical characteristics of alloy plates with different chemical composition. Besides, the galvanic current density and effective protection area of the corrosion protection system were discussed for solutions of various concentrations. Moreover, three types of corrosion tests were carried out to evaluate the effectiveness and durability of this system: the constant exposure test, accelerated exposure test, and atmospheric exposure test. The time-dependent anti-corrosion performance was discussed according to the characteristics of the corroded surface, and evaluated by discussing the effect of environmental variables and the exposed holes of the anode plates. The test results show that the sensitivity of the specimens to the changes in the environment is low, and that the cathodic protection current flows continuously, irrespective of whether it rained or not. In addition, the anode consumption of an Al-20Zn (mass%) alloy plate is the least, with good current efficiency, and an improvement in the anti-corrosion effect by adding elemental In to the anode plate cannot be expected. For all the test specimens, the current efficiency of the sacrificial anodes could on average reach about 70–80% in this system.

Boundary element method solution for large scale cathodic protection problems

Cathodic protection techniques are widely used for avoiding corrosion sequences in offshore structures. The Boundary Element Method (BEM) is an ideal method for solving such problems because requires only the meshing of the boundary and not the whole domain of the electrolyte as the Finite Element Method does. This advantage becomes more pronounced in cathodic protection systems since electrochemical reactions occur mainly on the surface of the metallic structure. The present work aims to solve numerically a sacrificial cathodic protection problem for a large offshore platform. The solution of that large-scale problem is accomplished by means of “PITHIA Software” a BEM package enhanced by Hierarchical Matrices (HM) and Adaptive Cross Approximation (ACA) techniques that accelerate drastically the computations and reduce memory requirements. The nonlinear polarization curves for steel and aluminium in seawater are employed as boundary condition for the under protection metallic surfaces and aluminium anodes, respectively. The potential as well as the current density at all the surface of the platform are effectively evaluated and presented.

Using the Gaussian function to simulate constant potential anodes in multiobjective optimization of cathodic protection systems

The purpose of this work is to numerically find the optimum location of constant potential anodes to ensure complete structure surface protection using a cathodic protection technique. The existence of sacrificial anodes is originally introduced through the boundary conditions of the corresponding boundary value problem (BVP). However, if constant potential galvanic regions are introduced through its boundaries, then finding their optimal location is not an easy task due to the necessity of redefining boundary geometric nodes and the arrangement of virtual sources for the standard method of fundamental solutions (MFS) formulation. Therefore, in this work, the galvanic anodes are introduced as source terms using a Gaussian function. Hence, the boundary remains the same for different anode positions. The optimization process includes the identification of the following parameters characterizing the Gaussian function: the optimum coordinates of the centre of the anode, a factor that involves the inherent potential of the electrode and a proportionality factor for the electrode diameter. The MFS methodology coupled with a genetic algorithm presented good results for this multiobjective optimization procedure. This fact can be seen in the several results of applications that are discussed in this paper, considering numerical simulations in finite regions in R2.

PIPELINE CORROSION CONTROL IN OIL AND GAS INDUSTRY: A CASE STUDY OF NNPC/PPMC SYSTEM 2A PIPELINE

Corrosion in pipelines is one of the major challenges faced by oil and gas industries all over the world. This has made corrosion control or management a major factor to consider before setting up any industry that will transport products via pipelines. In this study the types of corrosion found on system 2A pipeline were; pitting, microbial, sulfide-stress cracking, hydrogen-stress cracking and hydrogen-induced cracking and these were caused by poor maintenance of the pipeline system, severe mutilation of the pipeline coatings, substrates due to vandalization and coating failures. The data from cathodic protection control method from Nigeria National Petroleum Corporation (NNPC)/ Pipeline and Product Marketing Company (PPMC) for system 2A line was analyzed and it was deduced that about 10.3km of the pipeline was well protected and possibly fit for use and about 62.7km is experiencing under protection which means corrosion is predicted to take place in that segment in a short time and finally about 16km of the pipeline is experiencing corrosion. From the results obtained, it can be deduced that the use of cathodic protection technique as a method of controlling corrosion in oil and gas pipelines is effective and efficient when compared to other methods and thus constant monitoring is needed to achieve optimum efficiency. http://dx.doi.org/10.4314/njt.v35i2.11

Prevention of Steel Corrosion by Cathodic Protection Techniques

Prevention of Steel Corrosion by Cathodic Protection Techniques

The beneficial secondary effects of conventional and pulse cathodic protection for reinforced concrete, evidenced by X-ray and microscopic analysis of the steel surface and the steel/cement paste interface

The present study reports on the investigation of conventional and pulse cathodic protection (CP), in terms of steel surface analysis and investigation of the product layers at the steel/cement paste interface, after a long term (460 days) of conditioning and monitoring. The techniques used were: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX). Wet chemical analysis was used as supportive evidence for ion concentrations in the vicinity of the steel re-bars. Generally, CP promotes beneficial secondary effects i.e. enhanced OH - concentration and reduced Cl - concentration near the steel surface. Cathodic polarization also results in additional deposition of portlandite, which stabilizes the protective properties of the product layer on the steel surface. Consequently, the fundamental mechanisms, underlying the efficiency of CP techniques in reinforced concrete, are strongly related to beneficial secondary effects of CP, affecting the morphology and transformations of these product layers. Since the experimental evidences to support the aforementioned beneficial effects are rather limited, this study investigates the morphology and composition of the naturally formed steel surface layers, along with the properties of the steel/ cement paste interface, on corroding and protected steel reinforcement (in comparison to reference, non-corroding, non-protected conditions) after 460 days of conditioning. For the corroding specimens, the formation and substantial deposition of voluminous corrosion products, with low adherence to the steel surface is relevant (low protective ability), whereas in the protected specimens, a compact and adherent product layer of more stable high valent iron oxides, or calcium substituted such, was observed. To this end, the present work provides the experimental evidence for the fundamental mechanisms, related to the otherwise recognized positive secondary effects of CP in reinforced concrete.

Cathodic protection revisited: Impact on structural morphology sheds new light on its efficiency

Abstract Cathodic protection (CP) has been found as one of the most viable techniques for inhibiting chloride induced corrosion of steel in concrete structures. This contribution specifically pursues exploring the morphological alterations of corrosion products in reinforced mortars under cathodic protection. For this purpose, scanning electron microscopy (SEM) techniques are combined with energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) for microstructural analysis and quantification of the corrosion products. The combined characterisation provides important insight into the structural alterations induced by cathodic protection, and therefore, help to explain the efficiency of CP techniques. Furthermore, electrochemical measurements are employed to monitor the electrochemical process at the steel–paste interfaces. The beneficial microstructural alterations result in better corrosion resistance of the protected specimens, and turn out to be the mechanisms underlying the efficiency of CP techniques.

Concrete corrosion and control practices ‐ an overview

Concrete forms a major component of the national infrastructure. Corrosion of reinforced steels embedded in concrete has recently received wide attention in R&D programmes. Different cases have been reported showing failures of concrete structures which means huge loss. An attempt has been made to identify the different factors affecting the corrosion of embedded steel. Comparative evaluation of different protective schemes use of additives in concrete admixtures and the application of the cathodic protection technique has been discussed.

Study and Application of Impressed Current Cathodic Protection Technique for Atmospherically Exposed Salt-Contaminated Reinforced Concrete Structures

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Cathodic protection system

The basic aspects and mechanism of corrosion of steel piles in sea water are briefly discussed. The effects of parameters viz. pH, salinity, dissolved oxygen, temperature and wind velocity responsible for the corrosion of steel piles have been presented. The methods used for corrosion control and the impressed current cathodic protection technique in particular, with its merits, when applied to under‐water marine structures are outlined. The values and importance of potential required at the surface under protection, surface current density requirement and its distribution for the protection of steel structures under different service conditions useful for the design of cathodic protection systems are presented. The characteristics of various types of anode materials with a special reference to the latest platinized (Platinum‐Niobium) niobium anodes, with their merits, over other types of anodes are tabulated. The basic considerations required for the design of cathodic protection and the design of the system have been presented.

Novel technique of impressed current cathodic protection in atmospheric environments

A new cathodic protection technique has been developed for controlling atmospheric corrosion. A specially formulated coating, which contains the solid electrolyte sodium β″ (β) alumina as an ionically conducting component, not only isolates metal substrates from atmospheric environments, but also provides an electrical path for impressed protective currents. The feasibility of the technique has been verified by laboratory and field tests.

Corrosion Control of Kunifer-5 Seawater Piping Systems of Naval Ships by Cathodic Protection Technique

The cause of premature corrosion of Kunifer-5(copper alloy containing Ni 5 per cent and Fe 1.35 per cent) pipes used in seawater piping systems on board ships for feeding seawater to various units has been discussed. It has been shown that the Kunifer-5 alloys suffer from heavy corrosion-erosion attack at unavoidable bends and places where local seawater velocity exceeds the specified limit. The field observations as well as laboratory study have indicated that satisfactory protection of the pipes could be achieved by galvanic cathodic protection using aluminium alloy anodes.

パイプライン電気防食技術の現状

パイプライン電気防食技術の現状

AUTOMATIC IMPRESSED‐CURRENT, SACRIFICIAL, AND COMBINED CATHODIC PROTECTION SYSTEMS: PROTECTION FOR STEEL PROPELLERS

Impressed‐current cathodic protection techniques can be used to provide automatically the right amount of current at all times and, with the use of one or other of the systems described here, protection can be provided for the largest and the smallest vessel with any steelwork under water. This full range of equipment gives protection under the most varying conditions, and is considered by the manufacturers as being the most advanced system of cathodic protection in the world.

CATHODIC PROTECTION OF STEEL UNDERGROUND

Underground corrosion of steel pipe has been estimated to cost $600 million (approximately £200 million) annually, in the United States. Efforts to reduce this toll have been stimulated since 1941 by heavy defence requirements for steel and other metals. Workers in the field have learned that underground corrosion can be greatly reduced by cathodic protection techniques, in which the structure is maintained at a suitable negative electrical potential.