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Paper Number : 9002
Author : T.R.B. Watson |
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| This paper will concern itself with the very basic fundamental causes of corrosion. The fact is that metals corrode through sheer cussedness. They want to corrode. This perverse desire stems from the fact that it is much more natural for a metal to exist in the form of a compound, since the compounds such as oxides contain less energy than metals and are therefore more stable. |
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Paper Number : 10104
Date : 2/1/1978
Author : J.I. Munro
Notes : Water & Pollution Control |
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| Corrosion is best defined as "the process by which a material, usually a metal, combines with certain elements within its environment to produce a product that does not retain the useful properties of the original material". Unfortunately, this seemingly innocuous textbook definition does not convey the economic losses that result from corrosion damage. The minimum financial losses due to the "process" are well in excess of the combined annual costs of fires, floods, hurricanes, tornadoes, and earthquakes in North America. This article covers the cost, causes, and cures of industrial corrosion problems. |
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Paper Number : 11104
Date : 1/1/1977
Author : H.A. Webster
Notes : C.I.M. Conference |
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| Following a short review of corrosion theory, cathodic and anodic protection is described with reference to some practical problems that arise from the application of these techniques. |
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Paper Number : 11118
Date : --/88
Author : R.A. Gummow |
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| Most metals exposed to a liquid phase corrosive environment can be protected from aggressive corrosion attack using an electrochemical prevention technique, either cathodic protection (CP), anodic protection (AP) or potential adjustment protection (PAP). Which of these methods of protection is appropriate depends primarily on the metal/environment characteristics. |
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Paper Number : 11124
Date : 2/1/1990
Author : H.A. Webster
Notes : TUNS |
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| This article covers the thermodynamic and kinetic basis of corrosion. The atomic structure of elements, the properties of ions, and the part that acid and bases play in the corrosion process is discussed. Metallic corrosion is approached from an energy perspective using a Pourbaix diagram. The electrochemistry of corrosion leads into the examination of both anodic and cathodic polarization characteristics to illustrate the type of corrosion cell activity. |
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Paper Number : 13201
Date : Nov-98 & Dec-00
Author : J.I. Munro / W.W. Shim
Notes : Sulphur 98 Conf. & NACE Materials Performance |
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| This article discusses the use of anodic protection (AP) in combating iron contamination, general tank wall wastage, and hydrogen grooving in carbon steel sulfuric acid (H2SO4) storage tanks. It also addresses the use of AP for stainless steel acid piping and coolers. Topics include experiences using AP in acid storage tanks, theory of AP, design philosophy, engineering materials used, and remote monitoring equipment. |
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Paper Number : 13303
Date : --/83
Author : J.I. Munro |
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| Anodic protection has been shown to prevent corrosion of continuous digesters. Research indicates that this type of protection will also prevent caustic cracking in both soda and kraft vessels. The purpose of this paper is to familiarize pulp mill personnel with the basic mechanisms of corrosion and how anodic protection can be utilized to prevent these serious problems. |
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Paper Number : 13306
Date : --/85
Author : J.I. Munro |
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| Anodic protection systems have been installed in eight hydraulic continuous digesters and one impregnation vessel. Results indicate that corrosion and caustic cracking have been mitigated by the application of anodic protection. Operating characteristics, hardware improvements and digester inspection results are discussed. Potential and coupon monitoring systems using existing nozzles in digesters has proven to be an economical way to determine the susceptibility to corrosion and/or caustic cracking. |
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Paper Number : 13316
Date : 8/1/1992
Author : J.I. Munro
Notes : 7th Int'l P&P Symp. TAPPI |
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| Anodic protection is a powerful technique used to mitigate corrosion of liquor tankage. The large currents required for protection of a typical vessel led to problems in the first generation of commercial systems. This paper describes the cause of the problems and the solutions developed for successful protection systems. Use of protective linings utilized in conjunction with anodic protection shows great promise. |
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Paper Number : 13317
Date : Feb. & Mar-02
Author : J.I. Munro
Notes : NACE - Materials Performance |
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| Anodic protection is a powerful technique used to mitigate liquor tankage corrosion. The large currents required to protect a typical vessel led to problems in the first generation of commercial systems. This article describes what caused the problems and discusses the solutions developed for successful protection systems. |
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Paper Number : 13318
Date : Jun-02
Author : W.W. Shim
Notes : ABTCP Conference |
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| Anodic protection (AP) is a powerful technique for corrosion mitigation of white and green liquor tankage. Recent improvements are discussed. The use of Distributed Current Sources (DCS) resulted in decrease of: 1) mill personnel involvement, 2) logistical hurdles for repassivation, and 3) DC cabling costs. Current distribution design for AP system is critical and it must be based on primary current distribution. The liquor electrochemistry does not allow secondary or higher order current distribution design. Remote monitoring is an integral AP component ensuring that no active areas are allowed to exist in the tank. Full-length corrosion coupons are used to monitor the effectiveness of AP. Care must be exercised to ensure erroneous coupon results due to the effects of low resistivity liquor are minimized. |
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Paper Number : 13104
Date : 5/1/2001
Author : J.I. Munro / W.W. Shim
Notes : NACE Materials Performance |
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| Most metals will corrode within a certain range of electrical solution potential and solution pH. At potentials more negative than this range, corrosion ceases (cathodic protection). At potentials more positive than this range, several metals become passive. For these metals the potential can be shifted electropositively into the passive range through anodic protection (AP). AP is especially applicable to sulfuric acid (H2SO4) and caustic liquor environments. It often permits a designer to use a low alloy rather than a corrosion-resistant metal, at an overall cost savings. |
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Paper Number : 11111
Date : 5/1/1980
Author : J.I. Munro
Notes : "Pulp & Paper Industry" |
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Clarifiers are utilized by various chemical process plants, including the pulp and paper industry. Clarifiers are used to minimize the amount and toxicity of suspended solids in the effluent stream. The clarification process incorporates coagulation, flocculation, and sedimentation. The removal of suspended matter by settling without chemical coagulation is rarely encountered today.
There exist many designs for clarifiers; however, the emphasis of this discussion will be based on only one type of clarifier. The walls and floor are fabricated from steel reinforced concrete, while the center well, rake, and associated moving parts of the clarifier are constructed from mild steel.
Although clarifiers are the subject of this paper, much of the corrosion theory can be applied to holding and chemical mixing tanks without rake mechanisms. |
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Paper Number : 11114
Date : 5/1/1985
Author : C. Henderson |
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| The paper reviews the fundamental concepts of corrosion and corrosion control utilizing protective coatings and cathodic protection for mild steel piling in marine environments. Cathodic protection techniques and two types of coatings; flake glass polyester and coal tar epoxy are discussed. Practical applications for new construction and rehabilitation are described. |
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Paper Number : 11308
Date : 3/1/1998
Author : J.I. Munro / S.M. Segall
Notes : NACE Corrosion 98 |
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| Issues considered during the design of an impressed current type cathodic protection (ICCP) system for corrosion control on the submerged external surfaces of the steel ice shields on the bridge piers are presented. The challenges and cathodic protection (CP) system design solutions, associated with providing protection to the underwater CP components against ice damage, are discussed. The ICCP system is described including the different CP equipment arrangements utilized, based on the various pier configurations and construction methods. Results of the system effectiveness are also discussed. |
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Paper Number : 11140
Date : 2/1/2000
Author : R.A. Gummow / S.M. Segall / R.G. Wakelin
Notes : NACE Saskatoon (2/00) & NACE 2000 Orlando (3/00) |
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| Methods of determining the coating quality on directionally drilled pipe sections were investigated in a research project sponsored by the Pipeline Research Committee of the American Gas Association. Tests were conducted on FBE coated pipe samples which were buried in three different soil conditions and equipped with steel strip coupons to simulate coating damage. A field test procedure, which can be performed by a CP technician, was developed that estimates coating quality in terms of percentage bare. |
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Paper Number : 11401
Date : 11/1/2000
Author : R.A. Gummow
Notes : W.Cdn. NACE Conf. (2/80) Updated for EPIC (11/00) |
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Interference can be defined as any electrical disturbance on a structure caused by a stray current. In this context, 'stray' refers to a current in an unintended path, although it is recognized that current will take all available paths in inverse proportion to the relative resistance of each available path.
Corrosion as a result of interference from a DC transit system was first reported by Stone & Forbes in 1894, just six years after the transit system began operation. Their paper was entitled "Electrolysis of Water Pipes" and the term 'electrolysis' has persisted ever since to denote the corrosion attack on an underground structure caused by a stray current. Regional committees of underground utility representatives that were formed to discuss mutual electrical interference problems are called Electrolysis Committees.
Sources of stray current are any AC or DC systems that are grounded to the earth or use the earth as a current path. This includes both AC and DC power systems, cathodic protection systems, electrified transit systems, and telluric currents caused by the interaction of solar particles on the earth's magnetic field. |
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Paper Number : 11102
Date : --/65-66
Author : H.A. Webster
Notes : "Waterworks Man. & Dir." |
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| Soil bears the greatest responsibility for underground corrosion losses, and the differences in corrosion losses of different types of ferrous materials when in contact with the soil are very small indeed. Past histories of pipe performance usually relates to differences of soil composition, moisture content, and pipe thickness, rather than to the material of the pipe itself. |
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Paper Number : 11109
Date : 2/1/1983
Author : R.A. Gummow
Notes : W.Cdn. NACE Mtg. |
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| The cost of repairing or replacing watermain piping perforated by corrosion is becoming a major item in many municipal budgets, and correspondingly in most individuals' municipal taxes. In metropolitan Toronto, for instance, it is estimated that over $5 million will be spent in 1983 for repair, replacement, or renewal of domestic water piping systems. Winnipeg, which has perhaps the highest failure rate of any Canadian city, had approximately 2200 failures in 1982, requiring a $7.7 million program just to limit annual leaks to the 2200 level, which is a leak frequency of 1.1/km/y. Many cities such as Scarborough (North York), Edmonton, Calgary, and Saskatoon, have system leak frequencies of 0.5/km/y. In most of these cases, the water piping system is comprised principally of a mixture of gray cast iron and ductile iron. Although it is understandable that cast iron failures occur both from a mechanical and age point of view, one alarming experience is that ductile iron which was installed in the late 1960's and 1970's is also exhibiting a significant failure rate. Recent investigations, supported by previous studies, have indicated that corrosion is a primary cause of failures on both gray cast and ductile iron piping. As this fact has become recognized more widely by the waterworks industry, so has the need for corrosion prevention solutions. |
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Paper Number : 11113
Date : 2/1/1987
Author : C.R. Pynn |
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| The paper deals with the pipe failures due to corrosion experienced on the water distribution system of the Township of Emo, Ontario. Specifically, the detection and analysis of the problem; the evaluation of sacrificial anode arrangement; the development of a distributed impressed current cathodic protection system (i.e. DICCAP™) and performance history. |
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Paper Number : 11115
Date : 5/1/1988
Author : R.A. Gummow |
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The cost of rehabilitating the 38,000 km of water distribution piping in Ontario, currently valued at $21.2 billion ($2,725 per capita) has become a major focus of attention. Not only is it estimated that 15% of the water supplied is unaccounted for but the average annual breaks per 100 km is an astounding 25 resulting in annual emergency repair costs estimated at $65 million.
This Ministry of Environment report of January 1987 entitled "The Need for a Rehabilitation Program for Water Distribution Systems in Ontario" further estimated that the annual cost for replacing Ontario's water system would be $50 million assuming only 50% required reconstruction over the next 50 years. There is a major concern as to who will pay the cost of this rehabilitation since most current water rate charges are insufficient to provide replacement funding. Despite appeals for funding to all levels of government by the Ontario Sewer and Watermain Contractors Association, it is apparent that there is substantial resistance to these requests. Yet as the appeals for special funding echo through our industry, municipalities continue to repair about 9500 breaks annually with the expectation that this number will continue to grow. The Environment Ministry estimates however that if the break frequency could be reduced to 10 breaks per 100 km, then an annual savings of $15 million would be realized.
The question then arises as to whether or not the "break" rate can be practicably reduced. Numerous studies have identified corrosion to be the primary cause of both grey cast iron and ductile iron watermain failures. Accordingly, if the corrosion activity can be reduced then the service life can be proportionately extended and the "break" rate reduced. |
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Paper Number : 11125
Date : 9/1/1988
Author : C.R. Pynn |
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| This paper presents an economic model of a watermain, in terms of corrosion costs, as a tool for the waterworks engineer to assess the benefit of upgrading alternatives. The general effect of various upgrading alternatives are indicated using the model, and the steps for implementing a corrosion control program are outlined. |
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Paper Number : 11126
Date : 9/1/1989
Author : R.G. Wakelin |
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| This paper outlines the procedures used in designing a cathodic protection system for new or existing iron water piping. Both sacrificial and impressed current systems are discussed, and design examples for various applications of these systems are also given. |
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Paper Number : 11131
Date : 6/12/1905
Author : R.G. Wakelin / R.A. Gummow |
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| The data obtained from several municipal watermain corrosion studies in the Province of Ontario is presented. This data corroborates the findings of a previous study indicating that the galvanic couple formed by the connection of copper service piping to iron watermains is a principal factor controlling the watermain corrosion rates. Soil electrical resistivity is found to be of major importance only where this galvanic couple exists. A simple means of estimating the integrity of a watermain based on soil resistivity and service type is also presented. |
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Paper Number : 11132
Date : 6/13/1905
Author : R.G. Wakelin |
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This paper provides a summary of the statistical findings of several recent watermain corrosion studies conducted for municipalities in Southern Ontario. External corrosion rates are correlated with soil resistivity, chloride ion concentrations, pH, watermain material, and galvanic factors. Internal corrosion rates are correlated with watermain age and diameter, and are compared to external corrosion rates. Case studies of watermain failure histories are also presented for three municipalities.
The paper shows that where copper service piping is used, soil resistivity is the only soil characteristic which has a significant effect on the external corrosion rates. The corrosion rates of watermains connected to lead, galvanized iron, or ductile iron service piping, on the other hand, are found to be relatively independent of soil characteristics. Failure rates of iron watermains connected to lead or iron service piping are found to be consistently lower than those associated with copper service piping.
Internal corrosion rates are found to decrease exponentially with time, with large diameter mains generally exhibiting higher rates than small diameter mains, but the amount of internal surface area pitted is found to increase with time. Internal corrosion is found to result in a greater total loss of metal than external corrosion, but maximum internal pit penetration rates are limited to values much less than the maximum external rates.
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Paper Number : 11146
Date : 8/1/2004
Author : R.A. Gummow
Notes : Maintaining & Rehabilitating Wtrmns - EPIC Seminar |
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| External corrosion of iron watermains has been a problem for municipalities for over 100 years. The three main causes of corrosion, in a historical context are; stray currents from electrified transit systems, dissimilar soils, and galvanic corrosion. All of these causes remain with us today, although to varying degrees. |
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Paper Number : 11148
Date : 5/5/2005
Author : R.A. Gummow
Notes : NACE Materials Performance |
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| Prestressed concrete cylinder pipe (PCCP) used for water and sewer transmission service is composed of a thin wall steel cylinder, lined on the interior and exterior with cement mortar, and reinforced by prestressing wire either wrapped around the steel cylinder or embedded in the exterior mortar. These large-diameter composite pipes are often thought to be immune to corrosion because the steel cylinder and prestressing wire are covered by concrete whose alkalinity promotes the formation of a protective passive film on the steel surfaces. As with many passive films, however, the protective film is subject to breakdown by chlorides, and there have been an increasing number of failures on PCCP piping because of chloride attack. Once the film is penetrated and corrosion is initiated on the prestressing wires, which are typically under ~200 ksi (1,400 MPa) tension, stress corrosion cracking occurs, often causing catastrophic failure of a major water transmission main. |
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Paper Number : 11205
Date : 11/1/1983
Author : C.R. Pynn
Notes : E.Cdn. NACE Conf. |
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The failure of ductile iron water distribution systems due to corrosion is resulting in ever increasing annual maintenance costs in many communities. This experience has lead to a growing awareness of corrosion in general, and its prevention in particular, throughout the municipal waterworks industry. Realizing that, in many instances, cathodic protection is a cost-effective corrosion prevention technique to extend the service life of these piping systems, some communities have been installing sacrificial anodes along their ductile iron watermains.
To date, however, a general, industry-wide standard has yet to be established regarding the required anode alloy, dimensions, or spacing. The situation has been further complicated by some published material where the comparison between differently alloyed and dimensioned anodes has been either incomplete or limited to specific soil resistivities or current requirements.
The paper will; 1) review the standard structure potential and current requirement criteria employed in cathodic protection design, 2) review the characteristics and construction of magnesium and zinc sacrificial anodes, 3) review the calculations employed to determine anode output current and service life, and 4) present a general method for accurately comparing the cost-effectiveness of different anodes, independent of total current requirements, over the range of soil resistivities where they are typically employed. |
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Paper Number : 11210
Date : 2004
Author : R.A. Gummow
Notes : NACE N.W. Conf. Feb-04 (Victoria) & MP May-04 |
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| The service life of Mg anode cathodic protection systems installed on iron water mains has, in some instances, been significantly less than design calculations would predict. Testing of high-potential Mg alloys from various suppliers using the ASTM G97-89 test method indicates that efficiencies are widely variable and that the life of a Mg anode could be as much as 90% less than calculated, depending on the source of the Mg. The literature shows that various factors such as anode current density, anode oxidation reaction, anolyte chemistry, alloy chemical composition, and alloy microstructure can affect anode efficiency. Municipalities are advised to conduct tests for alloy composition, microstructure, and backfill composition on anodes from industry suppliers in order to ensure anode quality and maximum system life. |
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Paper Number : 11404
Date : 8/1/1999
Author : R.A. Gummow
Notes : Int'l Union of Radio Science (26th General Assembly) |
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Potential and current fluctuations on oil and gas pipelines attributed to telluric currents have been observed for many years by corrosion control personnel when conducting routine cathodic protection performance surveys. The impact of these geomagnetically induced currents has generally been considered more of a nuisance when measuring cathodic protection parameters than a serious corrosion concern.
Boteler has shown that the telluric voltage induced on a pipeline can be calculated using distributed source transmission line equations. He has shown that the magnitude of the telluric voltage (Vt) is not only a function of the direction and magnitude of the electric field but is also directly dependent on the length and the pipe's resistance to earth. These calculations when applied to modern well coated pipelines, suggests that telluric current effects may not be as innocuous as originally thought for pipelines located in Canadian latitudes.
For the corrosion control practitioner there are three main areas of concern as follows; corrosion during positive half cycles of the telluric wave form, accuracy of pipeline current and potential measurements to determine the level of cathodic protection (for comparison with industry criteria), and coating damage caused by excessively negative potentials during negative half cycles. |
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Paper Number : 11407
Date : 3/1/2000
Author : T. Place/O. Sneath
Notes : NACE Corrosion 2000 |
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| Transient phenomena can significantly affect the accuracy of pipe-to-soil potential (PSP) measurements. One pipeline operator has developed a simple method to improve the accuracy of cathodic protection close interval survey (CIS) measurements through the use of continuous dataloggers at reference locations within the survey area. |
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Paper Number : 11408
Date : 2/3/2003
Author : T. Place
Notes : NACE Northern Area Western Conference Calgary, Alberta |
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| Transient phenomenon can significantly affect the accuracy of pipe-to-soil potential (PSP) measurements. This paper discusses two methods of improving the accuracy of cathodic protection (CP) test station survey measurements that have been affected by geomagnetically induced currents (GICs). The effectiveness of these techniques is explored in the context of two pipeline surveys totalling more than 1200km in length. |
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Paper Number : 11409
Date : 3/1/2003
Author : B. Rix / D.H. Boteler
Notes : NACE Corrosion 2001 Paper No. 01317 |
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The Maritimes and Northeast Pipeline on the east coast of North America is constructed through an area where large geomagnetic disturbances can be expected. Because of this it was decided to include consideration of telluric current effects in the design of the cathodic protection (CP) system for the new pipeline.
An evaluation was made of the electric fields expected to be produced by geomagnetic disturbances. A computer model was set up to examine the pipeline response to these electric fields. This allowed calculations of the pipe-to-soil potentials produced with different coating resistances and placement of insulating flanges and groundbeds, which therefore allow various cathodic protection schemes to be evaluated before construction. The modeling showed that putting insulating flanges into the pipe created extra sites where large pipe-to-soil potentials would be produced. Accordingly, it was decided to make the pipe electrically continuous and drain the telluric currents off at the ends of the pipeline using potential-controlled rectifiers. This paper describes the CP system installed to mitigate the telluric current effects and presents observations of telluric currents both before and after commissioning of the CP system. |
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Paper Number : 11312
Date : 11/01/1991
Author : R.A. Gummow |
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A 1985 study conducted by the Canada Mortgage and Housing Corporation stated that the overall cost of repairs to damaged parking structures in Canada was estimated at 1.5 to 3.0 billion dollars. Little has been done in the intervening years to reduce these costs on existing parking structures. In fact, repair costs have escalated not only due to inflation but owing to more rigorous repair techniques since it is now recognized that the old methods of simply repairing a delamination does little to reduce overall corrosion. Unless all concrete containing greater than a threshold concentration of chlorides is removed, then corrosion continues unabated in non-repaired areas. It is now apparent that unless chloride contaminated concrete is removed, corrosion activity continues as long as the relative humidity remains above 50% at the reinforcing steel surface even if a membrane or sealer is applied since the chloride ions are not consumed in the corrosion process. Because of this, repairs have become more extensive and expensive, often involving hydrodemolition of large areas of a parking deck and in extreme cases complete removal and replacement of the slab. Many of these costly measures could have been avoided at considerable savings to the owners if cathodic protection had been used. The data presented in this paper will describe case history results on several cathodically protected structures based primarily on results of delamination surveys conducted by a number of civil and structural consultants.
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Paper Number : 11121
Date : 02/01/1989
Author : R.A. Gummow |
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The possibility that cathodic protection (CP) could successfully reduce corrosion on reinforced concrete structures exposed to the atmosphere was postulated by Finley in 1961 and later attempted on bridge decks by Stratfull and Fromm during the 1970's. Much of the research work into the types and operating characteristics of CP systems has been funded by the U.S. Federal Highways Administration which as a result issued a memorandum on December 31, 1981 that concluded "Research and field experiences with cathodic protection (CP) on the other hand, show that corrosion damage can be halted regardless of the salt content of the concrete". Although bridge structures are particularly susceptible to corrosion arising from the combined presence of air, moisture and chlorides from de-icing salts so also are reinforced concrete parking facilities. The earliest developed CP systems used a conductive asphalt overlay electronically connected to high silicon iron anodes but this type of system is not feasible for parking structures because of the inability of the parking reinforced structural slabs to support the substantial weight of the overlay.
As CP is probably the most cost effective corrosion control option for existing facilities, a number of alternative systems have been developed over the last decade which now make CP systems routinely applicable to parking structures. Presently, it is estimated in Canada alone that CP has been applied to over 500 thousand square meters of reinforced concrete parking decks. Most of these systems have utilized a conductive coating applied to the soffit as the primary anode instead of the overlay on the top surface. Other systems, applied to the top surface have utilized anode materials such as conductive polymer cables, and rare metal oxide coated titanium in a mesh configuration or platinum clad niobium wires implanted in sawed slots surrounded by a conductive grout. Regardless, before CP is applied to a reinforced concrete parking structure several factors must be considered. |
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Paper Number : 11128
Date : 02/01/1988
Author : R.A. Gummow
Notes : "Construction Canada" |
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| The paper covers the application of cathodic protection to reinforced concrete structures, such as parking garages, bridge decks, etc. The typical rebar corrosion process by de-icing salts is discussed in conjunction with the conventional rehabilitation measures, explaining why the repaired structures continue to deteriorate after repair. The cathodic protection technique is explained in detail, including the technical approach, the operating and maintenance requirements, and the cost benefits. |
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Paper Number : 11129
Date : 07/01/1987 |
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The corrosion of reinforcing steel in concrete structures is the most serious corrosion problem in Canada. A 1985 study prepared for the Canada Mortgage and Housing Corporation stated that "the overall cost of repairs to damaged parking structures in Canada has been estimated at 1.5 to 3.0 billion dollars".
It is well established that the corrosion of reinforcing steel is both initiated and sustained by the continual presence of chlorides, moisture and oxygen at the reinforcing steel/concrete interface. The corrosion mechanism, therefore, is aqueous which is similar to the corrosion action that attacks other steel structures exposed to an earth environment. Accordingly, the most appropriate solutions for prevention of reinforcing steel corrosion are the same ones that are successfully applied to other structures exposed to an aqueous chloride environment. In this respect, cathodic protection is the most dominant and successful corrosion prevention technique of all. |
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Paper Number : 11138
Date : 06/01/1997
Author : R.A. Gummow / J.I. Munro
Notes : TAPPI Conference |
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Soil side corrosion of surface storage tanks can be a serious problem. In many industries the life of the tank is limited by external corrosion of the tank bottom. Cathodic protection (CP) is a cost effective technique used to eliminate soil side corrosion and hence can indefinitely extend the life of the tank bottom and significantly increase the intervals between internal inspections as recommended in API 653.
Many owners are now installing secondary containment when constructing new tankage. Most of these containment liners are fabricated from non-conductive materials that may prevent the application of cathodic protection unless specific components are installed concurrently with tank fabrication. This paper will examine the corrosion mechanisms of tank bottoms as well as the various designs of CP systems with and without secondary containment. |
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Paper Number : 11142.1
Date : 03/04/2004
Author : R.A. Gummow
Notes : NACE Corrosion 2004, New Orleans, LA |
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| Although cathodically protected pipelines are often connected directly to electrical ground in stations and plants, there is little information on the amount of current required to polarize various grounding materials such as copper, tinned copper, stainless steel, silicon iron, and galvanized steel. This paper presents results of short and long-term cathodic polarization tests on commercially available grounding materials buried in a low resistivity clay and a high resistivity sand. The results indicate that in the non-aerated clay all the grounding materials, that would normally be cathodic to steel, required the same or less current density than steel. In the more aerated sandy soil, the current requirements for all the cathodic materials as well as steel increased by at least 2 orders of magnitude with copper requiring an increase of 3 orders of magnitude. Packaged zinc and magnesium anodes were also included in the testing program since they are occasionally used as grounding electrodes for cathodically protected pipelines. |
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Paper Number : 11144
Date : 02/04/2004
Author : J.I. Munro / O. Sneath
Notes : NACE Northern Area Western Conference, Victoria, BC |
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Copper grounding has a detrimental effect on cathodic protection (CP) of interconnected underground carbon steel piping. The copper can consume large amounts of protection current as well as introducing significant measurement errors when verifying the protection level of the piping.
This paper examines the interactions between copper grounding and pipeline systems as well as a cost effective solution to the problem. An actual case study is presented confirming that silicon iron can be used to replace copper electrodes resulting in effective electrical grounding with minimal impact on cathodic protection systems. |
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Paper Number : 11136
Date : 11/01/1993
Author : R.A. Gummow
Notes : "Materials Performance" |
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| This article traces the history and development of the -0.850 VCSE (copper sulfate electrode) potential criterion over the last 60 years with respect to thermodynamic considerations and empirical testing in both the laboratory and field. The significance of reference electrode position and IR-drop voltages for the protective potential measurement and the influences of soil resistivity, sulfate-reducing bacteria, and temperature on the effectiveness of the minimum potential value are reviewed. In addition, the hazards of overprotecting a steel structure with respect to hydrogen embrittlement and coating disbondment are considered. |
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Paper Number : 11139
Date : 02/01/2000
Author : R.A. Gummow
Notes : NACE Ottawa (10/99) & Materials Performance (2/00) |
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| Since its introduction in 1824, cathodic protection (CP) technology has developed to become a fundamental tool for preventing corrosion on municipal infrastructure. Potable water storage tanks and piping, prestressed concrete cylinder pipe, reinforced concrete structures, bridges, parking structures, underground fuel tanks, and effluent treatment clarifiers now benefit from this technology. |
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Paper Number : 11208
Date : 11/01/1993
Author : R.G. Wakelin
Notes : NACE Int'l Conf. |
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| This paper discusses some of the corrosion problems typically experienced by the underground portions of electrical transmission line towers, and examines cathodic protection as a method by which tower footing corrosion can be prevented. A case history of one power company's cathodic protection experiences is also presented. |
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Paper Number : 11403
Date : 03/01/1980
Author : J.I. Munro
Notes : NACE Corrosion 80 |
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| Reverse current electrolysis switches have been used for many years to minimize stray current corrosion damage to underground metallic structures. Various types of systems have been utilized with varying degrees of success. During the past thirty years the power electronics industry has come of age resulting in new, more reliable, high power devices for the corrosion engineer to utilize in the fabrication of reverse current switches. This paper will examine the need for such units as well as compare and optimize their usage. |
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Paper Number : 10207
Date : 03/01/1998
Author : R.A. Gummow / R.G. Wakelin / S.M. Segall
Notes : NACE Corrosion 98 Paper No. 566 |
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| Corrosion of steel by alternating current was investigated as far back as the early 1900's. These early studies and others in the 1950-60's indicated that AC corrosion of steel was only a fraction of an equivalent amount of direct current (i.e. less than 1% of a like amount of DC) and in addition was controlled to negligible levels when cathodic protection was applied to industry standards. In 1986 however, an investigation into a corrosion failure on a high pressure gas pipeline in Germany indicated that the sole cause of the failure was AC corrosion. This corrosion failure on an otherwise well protected pipeline resulted in the initiation of several laboratory and field studies which indicated, that above a certain minimum AC current density, normal levels of cathodic protection will not control AC corrosion to acceptable levels and that AC mitigation is often required to prevent serious corrosion. Several other AC corrosion sites were discovered at coating holidays during the follow-up investigations in Germany. A graph, relating AC voltage to holiday size at the minimum AC current density for corrosion, is presented to assist the pipeline operator in determining whether or not a pipeline is susceptible to AC corrosion activity. |
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Paper Number : 10208
Date : 03/01/1998
Author : R.A. Gummow / R.G. Wakelin / S.M. Segall
Notes : NACE Corrosion 98 Paper No. 565 |
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Literature dating back to the early 1960's has shown that AC current can cause corrosion of cathodically protected steel under laboratory conditions. Until recently however, there has been little evidence to suggest that AC corrosion of cathodically protected structures may be of practical concern.
In Ontario over the past six years, the authors have investigated several corrosion anomalies occurring on pipelines exposed to induced AC interference. This paper discusses a number of such cases where AC corrosion was suspected. The test procedures used to identify AC corrosion are discussed, as are some of the methods for minimizing the risk of AC corrosion.
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Paper Number : 11143
Date : 02/03/2003
Author : B. Woloschuk
Notes : NACE Northern Area Western Conference, Calgary, Alberta |
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| Regulatory agencies in Canada's oil and gas industry provide instructions for the monitoring frequency and criteria to be used for evaluating the performance of cathodic protection systems. Frequently, the actual monitoring of these systems is contracted out to third party service providers who may have divergent opinions of what constitutes an effective survey procedure. Incomplete current interruption, loss of rectifier synchronization, auto-rectification of induced AC voltages on pipelines, and lack of considering foreign current sources are only four survey difficulties that can make the difference between a valid and an erroneous CP survey. Modern equipment allows for effective consideration and evaluation of these potential difficulties, and also provides concrete documentation that allows the end user to audit the performance of their service provider. This paper provides information to end users with which to avoid the more common pitfalls that can invalidate cathodic protection pipe-to-soil potential survey data. |
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Paper Number : 11147
Date : 04/05/2005
Author : R. Reid / S. Segall
Notes : NACE Corrosion 2005, Paper No.05184, Houston, TX |
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| Under an Integrity Management Program (IMP) for natural gas transmission lines, the ECDA concept was analyzed and the process was validated from 2002 to 2004. A plan was developed and implemented in 2004 on one 17 km pipeline and segments of two other pipelines. This paper covers the Request for Proposal (RFP) methodology, the selection of a service provider, the execution plan and the results obtained. |
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Paper Number : 11149
Date : 03/01/2006
Author : S. Segall / R.A. Gummow / R. Reid
Notes : NACE Corrosion 2006, Paper No.06193, San Diego, CA |
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The paper describes the theoretical and practical aspects of merging two indirect inspection tools (i.e. Close Interval Potential Survey and DC Voltage Gradient) in one integrated survey, as used in 2004 during an ECDA project covering more than 21 km of gas pipelines in Southern Ontario.
A method was developed and verified in the field to calculate the %IR at coating defects using the recorded data, with no need to interrupt the survey or to return to the defect location in order to measure the total gradient to remote earth.
The data processing was improved by deriving the longitudinal gradient profile from the Close Interval Potential Survey data. This enhancement will be used in future surveys to validate indications, in conjunction with the measured lateral gradient data.
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Paper Number : 11309
Date : 03/01/2000
Author : G. John / T. Rosbrook / J. Robinson / J.I. Munro
Notes : NACE Corrosion 2000 |
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Due to failure of internal coatings in the high pressure and test separators on offshore production facilities, the option to install an internal cathodic protection system was considered. The background to the system selection (covering literature review, discussions with operators, laboratory study and computer modeling) are described.
The initial concept was to install a sacrificial anode system based on high-temperature zinc alloys. However, the prolonged shutdown required to install nearly 3000 kg of anodes in high-pressure separators was not economically viable (due to deferred production costs). Hence an impressed current system was designed. This required considerable engineering work to overcome objections on electrical safety grounds in the hazardous environment of an oil production facility. Detailed HAZOP studies were carried out and special protection systems incorporated to ensure safe operation. The final system installed is described together with preliminary data from the commissioning program. |
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Paper Number : 11310
Date : 03/01/2000
Author : O. Sneath
Notes : NACE Corrosion 2000 |
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| Monitoring the operation of cathodic protection (CP) systems on 39,000 km (22,000 miles) of pipeline through site visits and manual readings is a time consuming and costly task. Of the 1300 plus rectifier sites in the subject pipeline network, more than 40 sites are accessible only by helicopter and an additional 15-20 sites can only be accessed in the winter months by snowmachine, snowshoe or helicopter. Not only do the costs for performing this function lead one to investigate alternative solutions, but the philosophy of having corrosion technicians' carry out reactive instead of proactive work reduces their productivity. |
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Paper Number : 11405
Date : 10/01/1999
Author : D.H. Boteler / R.A. Gummow / B. Rix
Notes : NACE N.E. Area Conference (Ottawa) Paper No. 8A.3 |
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The Maritimes and Northeast Pipeline on the east coast of North America is being constructed through an area where large geomagnetic disturbances can be expected and where the electric fields produced will be amplified by the coast effect. In addition, the water movement associated with the rise and fall of tides in the Bay of Fundy (the highest tides in the world) will produce significant tidal electric fields. Because of these factors it was decided to include consideration of telluric current effects in the design of the cathodic protection (CP) system for the new pipeline.
An evaluation was made of the electric fields expected to be produced by geomagnetic disturbances and the tidal dynamo. A computer model was also set up to examine the pipeline response to these electric fields. This allowed calculation of the pipe-to-soil potentials produced with different coating resistances and placement of insulating flanges and ground beds. The modelling capability allowed various cathodic protection schemes to be evaluated before construction and has resulted in a more cost effective CP design for the pipeline. |
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Paper Number : 11406
Date : 02/01/2001
Author : R.A. Gummow
Notes : NACE N.W. Area Conf. (Anchorage) |
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| The impact of telluric current activity on the corrosion control systems on pipelines in northern regions and cold climates is examined. Three specific areas of concern are identified. These factors are; corrosion of the pipe during positive cycles of the telluric disturbances, accurate measurement of cathodic protection performance parameters, and coating damage during the negative cycles of the telluric activity. Corrosion rates are calculated versus the magnitude of the pipe potential change caused by discharging telluric current for different values of the Kp geomagnetic index. Methods of compensating and mitigating telluric current effects are discussed in the context of cathodic protection design and monitoring procedures. The benefits of using potential controlled rectifiers and integrated reference/coupons in mitigating telluric current effects are illustrated. |
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Paper Number : 12208
Date : 05/01/1990
Author : J.I. Munro / D. Singbeil
Notes : CPPA Conference |
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| More than 100 potential adjustment protection (PAP) systems for bleach plant washers have been installed over the past decade. Long-term monitoring data from these systems shows that electrochemical protection can more than double the lifetime of a bleach washer, sufficient to pay back the capital and operating costs in one year. |
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Paper Number : 12301
Date : N/A
Author : J.I. Munro / E.R. Dille / G.E. Moller
Notes : NACE Corrosion 84 |
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Ten flue gas desulfurization (FGD) scrubber towers in Units 1 and 2 of the double-loop limestone scrubber complexes at the Laramie River Station of the Missouri Basin Power Project were fabricated from chromium-nickel-molybdenum-iron alloys -- 904L, 316L, 317L, Alloy 825, Alloy G, and Alloy 625. The performance of these alloys has been essentially corrosion-free in the upper quencher, absorber, outlet duct, inlet duct, and dampers of the scrubber towers. Severe attack of 904L has been experienced in the quencher sump tank areas adjacent to welds, in areas of heat tint, in areas of weld spatter, in areas of heavy grinder and scratch marks, beneath paint, and in the free-field portion of some plates. The quencher sumps were repaired with ENiCrMo-3 welding rods. The welds were then pickled and passivated with a nitric-hydrofluoric acid mixture. For long-term performance, each of the quencher sumps has been retrofitted with electrochemical protection. This supplemental protection has performed well since installation and welding repairs in the quencher sumps have virtually ceased.
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Paper Number : 12303
Date : 03/01/1998
Author : W.W. Shim / E.R. Dille
Notes : NACE Corrosion 98 |
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Austenitic chromium-nickel-molybdenum-iron alloys (904L, 316L, 317L, etc.) used to construct Flue Gas Desulfurization (FGD) scrubbers and associated equipment in coal fired generating stations can experience localized corrosion. The problem may be alleviated by using more costly materials such as higher grades of stainless steel or high nickel alloys. An alternative and more cost-effective method of prolonging equipment service life is the use of potential adjustment protection, an electrochemical protection system (EP). Weight-loss coupon results in environments similar to FGD scrubbers have shown that the use of electrochemical protection prolongs the life of stainless steels in oxidizing acid-chloride environments by an average of 3 to 5 times.
This paper discusses an EP system that was recently supplied to an electric power utility company to protect a 316L thin metallic lined (wallpapered) FGD scrubber reaction tank. Acidic effluent from the absorber section of the scrubber is piped into this reaction tank for limestone neutralization and hence formation of calcium sulfate. Inspection of the protected reaction tank after one year of operation as well as in-situ coupon test results indicated that the EP system was very effective in mitigating localized corrosion of the scrubber reaction tank. The results are presented in this paper.
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Paper Number : 12304
Date : 08/01/1999
Author : E.R. Dille / K. Frizzell / W.W. Shim
Notes : MEGA Symposium |
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| At Owensboro Municipal Utilities, Elmer Smith Station, localized pitting corrosion had penetrated the 1/2-inch walls of the flue gas desulfurization (FGD) stainless steel 317LMN reaction tanks after two years of operation. In addition, thiosulfate pitting, crevice corrosion, and oxygen concentration cell corrosion have been found. Photographs of the corrosion and analytical data of the corrosive environment in the reaction tank will be presented. An electrochemical protection (EP) system has been installed to control all the previously listed forms of corrosion. Actual operating data will be presented. Significant cost savings are realized over conventional corrosion control techniques. |
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Paper Number : 12305
Date : 03/01/2000
Author : W.W. Shim / E.R. Dille
Notes : NACE Corrosion 2000 |
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| At three flue gas desulfurization (FGD) systems, localized pitting corrosion, thiosulfate pitting, and crevice corrosion has occurred on the inner surfaces of fourteen stainless steel FGD reaction tanks. An electrochemical protection (EP) system is installed on each of these fourteen FGD reaction tanks to control all the previously listed forms of corrosion. Corrosion data shows that the previous corrosion is under control. Significant cost savings are realized over conventional corrosion control techniques. |
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Paper Number : 12306
Date : 08/04/2004
Author : E.R. Dille / K. Frizzell / W.W. Shim
Notes : NACE AIRPOL Symposium (Washington, DC) |
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| A proven technique for the construction of low cost flue gas desulfurization (FGD) scrubbers and associated tanks is presented. Since 1981, electrochemical Potential Adjustment Protection (PAP) systems have been protecting stainless steel against the corrosive FGD environment. To date 14 FGD scrubber reaction tanks with PAP systems, fabricated of various low alloy stainless steels, have resisted corrosion where higher chromium/nickel/molybdenum alloys would have been mandatory. Performance data and cost data will be presented to allow designers of FGD systems to specify the proven PAP technique. |
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