Analysis of stray current induced by cathodic protection on steel-framed masonry structures

Cathodic protection (CP) has been successfully employed to protect steel-framed masonry buildings from corrosion related damage. When a CP system is installed to protect the structural members, other metallic items which are within the fabric of the structure but are not in direct electrical continuity may suffer from stray current interactions, resulting in accelerated corrosion of the discontinuous items. Therefore, these must be considered when CP systems are designed prior to installation. This paper presents both experimental and numerical studies into the risk and extent of stray current corrosion in steel-framed masonry structures when subject to impressed current cathodic protection. The objective is to allow CP systems to be optimised so that interference is minimised without compromising the technical or cost benefits of this method of corrosion control

Cathodic protection of steel framed masonry structures - experimental and numerical studies

Many high-profile steel-framed masonry buildings are susceptible to extensive damage as a result of corrosion of the steel frame. This has resulted in serious consequences with respect to serviceability, safety, aesthetics and heritage. Cathodic protection (CP) is a proven method for preventing and protecting buried and submerged steel and reinforced concrete structures from corrosion. More recently, the method has been introduced to prevent and control corrosion in steel-framed masonry structures. However, despite several sizeable CP installations around the world, there are no formal guidelines for the design, installation and operation of such systems and much of the knowledge is based on empirical observations. This paper presents both experimental and numerical studies on the cathodic protection of representative steel framed masonry structures. These studies are considered essential in the understanding of the mechanisms of cathodic protection and the design of optimised cathodic protection systems for such structures

HIGH-ORDER INTEGRAL EQUATION METHODS FOR QUASI-MAGNETOSTATIC AND CORROSION-RELATED FIELD ANALYSIS WITH MARITIME APPLICATIONS

This dissertation presents techniques for high-order simulation of electromagnetic fields, particularly for problems involving ships with ferromagnetic hulls and active corrosion-protection systems. A set of numerically constrained hexahedral basis functions for volume integral equation discretization is presented in a method-of-moments context. Test simulations demonstrate the accuracy achievable with these functions as well as the improvement brought about in system conditioning when compared to other basis sets. A general method for converting between a locally-corrected Nyström discretization of an integral equation and a method-of-moments discretization is presented next. Several problems involving conducting and magnetic-conducting materials are solved to verify the accuracy of the method and to illustrate both the reduction in number of unknowns and the effect of the numerically constrained bases on the conditioning of the converted matrix. Finally, a surface integral equation derived from Laplace’s equation is discretized using the locally-corrected Nyström method in order to calculate the electric fields created by impressed-current corrosion protection systems. An iterative technique is presented for handling nonlinear boundary conditions. In addition we examine different approaches for calculating the magnetic field radiated by the corrosion protection system. Numerical tests show the accuracy achievable by higher-order discretizations, validate the iterative technique presented. Various methods for magnetic field calculation are also applied to basic test cases

A study on the effect of the impressed current cathodic protection system in reinforced concrete structures

Reinforced concrete has been used as a construction material at variable fields related to our life such as air port, bridge, and ocean concrete structure, etc. The rebar in the concrete is protected from the corrosion because the passive layer is formed by high alkaline environment. Over the time, however, the rebar in the concrete is prone to corrode according to the corrosive environment and the structure of the concrete building. For example, the chloride ion plays a key role in corrosion process because it breaks the passive layer on the rebar and accelerates the corrosion rate. Besides, the volume of rebar is increased by the consequence of corrosion and then the concrete is spalled simultaneously. The cathodic protection was invented and used widely to protect rebars in the reinforced concrete structure against the corrosion. Additionally, The cathodic protection is divided to Sacrificial Anode Cathodic Protection (SACP) and Impressed Current Cathodic Protection (ICCP). Although ICCP system is expensive to install initially and is complex, this is applied more frequently to impede the corrosion in reinforced concrete structure than SACP. It explains roughly; ICCP supplies the protection current from the anode to the cathode (rebar) and then it prevents the corrosion of rebar and delays the corrosion rate. In complex RC structure, there are limitations on SACP system such as concrete resistivity, throwing power of CP and experimental environment, so it is difficult to expect to protect perfectly. Therefore, it needs to investigate the major factors having effect on the whole protection in complex structure of the building. However, ICCP is exploited as a practical way primarily to protect the corrosion of rebar in the concrete these days. For this study, the anode such as Ti-Mesh, Ti-Rod and Ti-Ribbon was installed on the reinforced concrete specimen of beam and slab type. In addition, the electrochemical test was conducted to confirm the cathodic protection performance depending to the exposed environment and the kind of anode in RC structure applied with ICCP ; E-log i, cathodic protection potential, depolarization, cathodic protection current. The following results have been obtained through the present study about the cathodic protection efficiency : 1) The E-log i test was conducted to affirm the standard of cathodic protection potential on the beam type specimen according to the environment. The standard value of cathodic protection potential was measured to about 90 ~ 140 mV. Besides, the value depending on the corrosive environment was inclined to increase slightly in order of atmosphere, fresh water and 3% NaCl solution. However, the kind of anode for ICCP nearly had no effect on the cathodic protection efficiency. 2) The cathodic protection potential was gauged by the galvanicstatic method on the beam type specimen applied with ICCP. The shape of anode had not major effect on the behavior of cathodic protection potential. In addition, the value of protection potential was tended to decrease in order of atmosphere, fresh water and 3% NaCl solution and then it was trivial difference between them. 3) The cathodic protection current was measured by the potentiostatic method after applying with ICCP on the beam type specimen and the degree of cathodic protection current was increased by all anodes in order of atmosphere, fresh water and 3% NaCl solution. 4) The degree of depolarization was investigated on beam type specimen. The IR-Drop was the highest in atmosphere because of the concrete resistivity. On the other hand, it was the lowest in the 3% NaCl solution. Moreover, when the corrosiveness of experimental environment was higher(more severe), the real degree of depolarization except IR-Drop was more increased by concrete resistivity. 5) The cathodic protection potential was evaluated on the slab type specimen. When the distance from the anode to the rebar(cathode) is closer, the protection potential was lower by the concrete resistivity. Additionally, the potential difference represented proportionally 50 mV per 60 mm which was the distance between rebars. 6) In protecting the slab type specimen by ICCP, as the distance between the location of rebar and the anode was farther, the concrete resistivity was increased more and then the supply of protection current was limited. However, after installing the anode at regular distance supplementarily, the unprotected rebar was enabled to protect well totally. 7) As the results of protecting the slab type specimen by ICCP, it would be able to find the maximum protection distance which is about 150 mm to the rebar from the anode. That is, the anode should be installed at interval of about 300 mm to protect the whole rebars uniformly without the unprotected area. It was found through the above results that the shape of anode used by ICCP had insignificant effect on the protection efficiency. The protection efficiency of ICCP was changed in accordance with the spacing between the anode and rebar, and the location of anode. So, it should consider those points throughly in designing the impressed current cathodic protection. In addition, when the proper cathodic protection is applied to the reinforced concrete structures, the enormous economic problems by the corrosion will be resolved as well as the safety for human life.|철근 콘크리트는 건축 재료로서 우리의 삶과 연관된 공항, 교량, 해양 구조물 등 다양한 분야에서 사용하고 있다. 콘크리트 내부에 있는 철근의 경우, 콘크리트 특유의 고 알카리성 환경으로 인해 철근 표면에 부동태 피막을 형성한다. 그러므로 부식을 피할 수 있게 된다. 그러나 시간이 경과하면서 부식성 환경과 건물의 복잡한 구조에 따라 철근은 쉽게 부식된다. 예를 들면, 염소 이온은 철근 표면의 부동태 피막을 파괴하고 부식속도를 가속화하는 주요한 부식성 요소이다. 게다가, 부식에 의해 철근의 부피가 증가하고, 동시에 콘크리트의 부서짐 및 탈락현상이 발생한다. 철근 콘크리트 구조물의 방식을 위해 음극방식법이 개발되었고, 널리 사용되고 있다. 게다가, 음극 방식법은 희생양극식과 외부전원식으로 나뉜다. 비록 외부전원식 음극방식법은 초기 설치 비용이 많이 들며 구조가 복잡하지만, 철근 콘크리트 구조물의 경우 희생양극식 음극방식법보다 주로 사용되고 있다. 외부전원식 음극 방식법을 간략히 설명하면 시스템 내의 음극과 양극 사이에 방식전류를 공급하여 방식을 시행하고 방식 속도를 늦춰주는 역할을 한다. 복잡한 구조의 철근 콘크리트의 경우, 희생양극식 음극 방식법은 콘크리트 비저항, 음극방식 시스템의 전달력 그리고 실험 환경 등의 방해 요소에 의해 완벽한 방식을 기대하기 어렵다. 따라서 복잡한 구조로 된 건물의 전체적인 방식에 영향을 주는 요소들을 조사할 필요가 있다. 그러나 외부전원식 음극방식법은 콘크리트 내부의 철근을 방식하기 위하여 오늘날에 사용하고 있는 가장 적절한 방법이다. 본 연구에서 Ti-Mesh, Ti-Rod, Ti-Ribbon 양극을 보(Beam) 및 슬랩(Slab) 형식의 철근콘크리트 시험편에 설치하였다. 그리고 외부전원법이 적용된 철근콘크리트 구조물의 노출환경 및 양극의 종류에 따른 음극방식성능을 확인하기 위하여 E-log i, 음극방식전위, 복극 그리고 음극 방식 전류와 같은 전기화학적인 실험을 실행한 결과 다음과 같은 결론을 얻었다. 1) 보 시험편에 대한 환경별 음극방식 전위 기준을 확인하기 위한 방법으로 E-log i 측정 실험을 시행한 결과, 음극방식 전위기준 값은 약 90~140 mV 로 측정되었다. 또한 부식 환경별로 음극방식 전위기준 값은 공기, 청수, 해수 순으로 약간 증가하는 경향이 나타났으나 양극의 종류와는 거의 무관한 결과를 나타내었다. 2) 정전류법으로 보 시험편에 음극방식을 적용한 후 방식전위 측정 결과 양극의 종류는 방식전위거동에 큰 영향을 미치지 않았으며, 부식 환경별로는 공기, 청수, 해수 순으로 방식전위 값이 낮아지는 경향이 나타났으나 그 차이는 크지 않았다. 3) 정전위법으로 보 시험편에 음극방식을 적용한 후 방식전류 측정결과 3 종의 양극 모두 공기, 청수, 해수 순으로 방식전류량이 증가하였다. 4) 보 시험편에서 복극량을 측정한 결과, 콘크리트 비저항에 의한 전압강하가 공기 중에서 가장 큰 값을 나타냈고, 3% 염수 환경에서 가장 낮게 나타났다. 또한 부식성 환경이 가혹할수록 비저항에 의한 전압강하를 배제한 순수한 복극량이 더욱 증가함을 확인할 수 있었다. 5) 슬랩 시험편의 방식전위 측정결과, 콘크리트 비저항으로 인하여 철근의 위치가 양극에서 가까울수록 방식전위가 낮아지는 것을 확인할 수 있었으며, 철근이 배근된 간격 60 mm당 약 50 mV씩 비례적으로 전위차가 발생하였다. 6) 슬랩 시험편을 외부전원법으로 방식할 경우, 철근의 위치가 양극과 멀어질수록 콘크리트의 비저항이 증가하여 방식전류의 공급이 제한되었으나 일정 간격으로 양극을 추가적으로 설치함으로써 미방식 되었던 철근까지 방식할 수 있었다. 7) 슬랩 시험편을 외부전원법으로 방식한 결과, 양극이 설치된 위치에서 약 150 mm 떨어진 철근까지 방식할 수 있었다. 즉, 미방식되는 영역이 없이 전체의 시험편을 균일하게 방식하기 위해서는 양극을 약 300 mm 간격으로 설치해야 한다. 이상의 결과를 통해 외부전원식 음극방식에 사용되는 양극의 형상은 방식성능에 큰 영향을 미치지 않음을 확인할 수 있었다. 또한 외부전원법은 양극과 철근과의 배치간격 및 양극의 설치위치에 의해 방식성능이 달라지기 때문에 외부전원식 음극방식 설계 시 이를 충분히 고려해야 한다. 게다가, 철근 콘크리트 구조물에 적절한 음극방식을 적용하면 막대한 경제적인 문제뿐만 아니라 인명안전 문제를 해결할 수 있으리라 사료된다.Table of contents i List of tables iii List of figures iv Abstract vii Chapter 1 INTRODUCTION 1 Chapter 2 BACKGROUND 4 2.1 Corrosion basics 4 2.1.1 Definition of corrosion 4 2.1.2 Thermodynamic and electrode potential 6 2.1.3 Electrochemical reactions in aqueous 11 2.1.4 Polarization 13 2.1.5 Passivity 18 2.2 Corrosion of steel in reinforced concrete 21 2.3 Corrosion of steel by chloride in reinforced concrete 24 2.4 Cathodic protection of reinforced concrete 26 2.4.1 Sacrificial Anode Cathodic Protection (SACP) 26 2.4.2 Impressed Current Cathodic Protection (ICCP) 29 Chapter 3 LITERATURE REVIEW 31 3.1 Availability of cathodic protection in reinforced concrete 31 3.2 Effect of CP in chloride environment 35 3.3 Arrangement and type of anode for ICCP in RC 39 Chapter 4 EXPERIMENTAL PROCEDURES 45 4.1 Specimens 45 4.2 Manufacture of anodes for ICCP and installation 48 4.3 Installation of test devices 50 4.4 Procedures & analysis 53 4.4.1 Measurement of E-log i on the specimens 53 4.4.2 Measurement of cathodic protection potential 55 4.4.3 Measurement of depolarization potential 56 4.4.4 Measurement of cathodic protection current 57 Chapter 5 RESULTS & DISCUSSION 58 5.1 Results of measuring E-log i on the beam type specimens 58 5.2 Results of measuring cathodic protection potential 60 5.3 Results of measuring depolarization potential on the beam type specimens 62 5.4 Results of measuring depolarization potential on the slab type specimens 66 5.5 Results of measuring cathodic protection current 70 Chapter 6 CONCLUSION 73 Reference 76Maste

Performance Assessment Of Sacrificial Anode Cathodic Protection Of Subsea Pipeline

The integrity of subsea pipeline depends mostly on the applied corrosion control. One of the corrosion control methods is using sacrificial anode cathodic protection, SACP. The performance of sacrificial anode cathodic protection is measured by the current supply and the operational life of the anode to protect the pipeline. In order to maintain the integrity of sacrificial anode cathodic protection, frequent inspection has been taken. However, there are no further assessment or analysis towards the performance of anode. The condition protection system only relies on the subjective data provide by the inspector. This study include aluminium and zinc as the sacrificial anode and carbon steel API 5L X65 as the cathode. The Objective of this study is to analyse on the corrosion rate of aluminium and zinc as well as to determine the most effective metal as a function of sacrificial anode metal. In this study, data are gathered from PETRONAS Carigali Sdn. Bhd. Peninsular Malaysia Operation, PCSB PMO. Two of their operating pipeline with different type of anode were selected and have been analysed on the corrosion rate of the sacrificial anode cathodic protection. Other than that, this study also includes data from laboratory simulation which are Linear Polarization Resistance test and weight loss test. As a reference, Det Norske Veritas, DNV RP B401 was used in order to design the sacrificial anode cathodic protection. Based on the results, it has been found that the corrosion rate of aluminium is higher than the other metals that are carbon steel API 5L X65 and zinc. To conclude this study, aluminium is found to be the most effective metal as sacrificial anode cathodic protection based on the corrosion rate, operational life and the current supplied by the metal

Disseny de protecció catòdica d'estructures offshore/màster

Based on the standpoint of the environment, corrosion is an environmental occurrence that is required to maintain the natural balance. From the engineer’s standpoint, this natural balance is observed as a damaging natural attack on a metal by an electrochemical reaction. This natural attack has various types such as uniform, crevice or pitting corrosion and it results in severe material loss, which contributes to lost production and increased maintenance, repair, and replacement costs, as well as restoration costs. Hence, prevention of corrosion is quite significant for metal to be applied in an offshore platform

Cathodic Protection Attenuation Near Tidal Zone Area

Pipeline is widely used in the offshore industry to transport all the oil and gas product from the offshore platforms to the onshore facilities. Large investment has been made by most oil and gas company in order to make sure offshore pipelines could last for their design life. So far, cathodic protection system and coating protection are the best solution in order to control the corrosion process along the pipeline. Over the years, cathodic protection has doing great in controlling the corrosion process for all offshore pipeline which either been buried or being laid in the deep water. However, the corrosion problems for pipelines near tidal zone area seems to have been overlook by the people in this industry. All these years, pipeline coating has been widely used in order to protect the pipeline in the tidal zone area. Generally, this research will study and analyze the response of cathodic protection system near tidal zone area. It will focused more on finding out the cathodic protection potential at tidal zone area close to shoreline. A few equations is being used and adapted with cathodic protection design from PETRONAS PMO in order to find out the dissipation of cathodic protection potential at tidal zone area. It seems that sacrificial anode does not function effectively in tidal zone area due to the absence of stable seawater electrolyte. Sacrificial anode needs a stable electrolyte around the metalwork to enable the anode to function effectively