ABSTRACT With burning of municipal solid waste (MSW), the potential for corrosion and tube wastage is always present. This is mainly due to certain corrosive substances in the refuse and some of its other constituents. There are two approaches to corrosion control, either prevention by conservative design, or by utilization of corrosion resistant materials. This paper will describe both of these corrosion control methods, with specific emphasis on application and experience. Both mass-burn and refuse-derived-fuel (RDF) systems will be addressed.
INTRODUCTION MSW is one of the most difficult fuels to burn because of its heterogeneous and highly variable nature. This mixture of household, commercial, institutional and industrial wastes provides special challenges during the handling and burning process. Depending on the refuse components and their variation, MSW ranges from relatively easy to very difficult to burn. The main problem is encountered with commercial and industrial wastes and their constitution, or possibly some other aspects such as sizing, moisture fluctuation, high chlorine content, etc. Because of the refuse composition and characteristics, the corrosion potential is always present. Acid gasses, specifically HCI, and some metals such as lead, zinc and tin, are the major contributors to the corrosion process. As refuse boilers are designed for ever higher steam conditions (pressure and temperature), many boiler components, specifically the tubes, are increasingly susceptible to corrosion.
It is most important to understand these issues and to properly address them.
ABSTRACT The influence of iron-oxidizing bacteria, Thiobacillus ferrooxidans, grown in a ferrous ion-free medium, on the corrosion of type 304 stainless steel (UNS S30400) was evaluated. Electrochemical measurements were performed, both in the inoculated and in the sterile media. Corrosion potential (Ecorr) for type 304 stainless steel exposed in the bacterial culture was shifted near +230 mVvs S. C.E. Cyclic voltammogram showed significant differences, a reduction peak was detected near -400 mV vs S. C.E. in the presence of the bacterial culture. This effect was most probably due to small quantities of Fe(III) compounds in the culture caused by iron-oxidizing bacteria. These results indicated that bacterial metabolic products affected the corrosion process, although they were able to cause initiation of corrosion of type 304 stainless steel.
INTRODUCTION Iron-oxidizing bacteria were implicated in microbially induced corrosion. The organism, Thiobacillus ferrooxidans, has been described as an obligate autotrophic bacterium that can transport ferrous iron into the cell, oxidize it to the ferric state, and transport it out of the cells. Several studies have been conducted to investigate the effect of iron-oxidizing bacteria on the corrosion of various mater ials3?4?5. Traditionally, iron-oxidizing bacteria have been reported to be important in the corrosion process, promoting differential aeration cells and providing oxygen depleted conditions due to their ability to oxidize ferrous ion to ferric ion. However, an investigation into whether iron-oxidizing bacteria accelerate initiation of corrosion has not been conducted. Recently, it has been reported that microbial colonization of passive metals could shift corrosion potential(EMCOR) in the noble direction. The phenomena of ennoblement has been variously ascribed to an increase in cathodic current density7, depolarization of the oxygen reduction react ion8?g, the combined effect of elevate dHz Oz and decreased p Hi, and production of manganic oxidell, etc. From a technical perspective, ennobled potentials can exceed critical pitting potentials for stainless steel, increasing the risk of localized corrosion. Once initiated, localized attack may proceed rapidly due to the enhanced cathodic depolarization.
The purpose of the present study was to investigate the mechanism of initiation of corrosion of type 304 stainless steel in freshwater containing iron-oxidizing bacteria and focusing particularly on the electrochemical phenomenon of ennoblement. Ferrous ion-starved iron-oxidizing bacteria were used to measure corrosion potential. The cyclic voltammetry was applied to evaluate the effect of the bacteria on the corrosion initiation process. Experiments were conducted using type 304 stainless steel immersed both in a sterile and in an inoculated media under two different conditions, air-purge (aerated) and argon-purge (deaerated).
ABSTRACT The U.S. Army has developed a proving ground accelerated corrosion and durability test for military vehicles. The test was based on the automotive testing developed by the General Motors Corporation and the SAE Automotive Corrosion and Prevention (ACAP) working group. Since it was initially used for High Mobility Multi-Wheeled Vehicle (HMMWV) off-road testing, the test included a combination of durability and corrosion inputs to achieve a target corrosion rate while performing activities that conform to a typical military vehicle mission profile. The testing is intended to achieve corrosion and material performance data that may be correlated to years of service in a highly corrosive military vehicle environment.
BACKGROUND Prior to 1950 catastrophic corrosion on automobiles was not considered to be problem. From the 1950?s to the 1970?s body corrosion became an increasing a significant problem on automobiles, with body perforation a major concern by the 1970?s. 1 By 1975 the cost of corrosion on -. automobiles was estimated to be $16 billion, roughly 20% of the total cost of corrosion that year.
In order to evaluate new and existing materials for use in automotive applications, many accelerated test procedures were developed. Accelerated test procedures include those that were performed in laboratory cabinets and on specially designed proving grounds. Laboratory~ cabinet testing is a relatively inexpensive way to obtain corrosion performance on components and to compare alternative materials. Proving ground testing is considerable more expensive, but allows one to evaluate all of the materials as a complete system ? including typical input stresses that a vehicle experiences. Of course, service exposure data would be required to correlate the field testing to the intended service environment.
This paper focuses on materials testing in proving ground tests. Incorporating periodic chemical and environmental inputs into a standard durability test procedure increases the natural corrosion rates of vehicle components. Vehicles assembled as close to a production vehicle as possible are driven through a course representative of the typical driving environment.2 It is the combination of these corrosion and driving/durability inputs that make this such a valuable test. Not only does this allows for many years of cosmetic corrosion to be simulated in a condensed time frame, but can show the potential functional problems related to corrosion of vehicle components.
It is important to recognize that environmental factors are accelerated to varying degrees. For example, although we can simulate 10 or more years of cosmetic corrosion on coated steel, other factors leading to the degradation of petroleum products, like oils and greases, are not accelerated. Thus care must be taken when evaluating these materials in the test. Routine maintenance involving oils and greases is commonly scaled to vehicle mileage rather than accelerated test duration. Careful consideration must be given to the evaluation of petroleum based coatings (e.g., under coatings) when conducting accelerated corrosion tests. Crevice corrosion within door flanges and sheet metal seams is also accelerated at a different rate than cosmetic corrosion. Although the test may have successfully simulated 10 years of cosmetic corrosion, there may have only been the equivalent of 3 years of crevice corrosion. Each of these acceleration factors is dependent on the service environment. Correlation to data obtained from vehicles in a variety of environments is essential to proper interpretation of test results.
ABSTRACT A microbiologically fouled industrial cooling water system was investigated utilizing a portable corrosion and fouling monitor according to the NACE RP0189-951 Standard. Baseline data was established and at which time the monitor was subjected to various dispersants (3) typically used for organic and microbiological deposit removal. The results of this in-field, side stream, experiment on a dynamic system will be presented. A number of key points and factors influencing the performance of the foulant clean up will also be discussed.
INTRODUCTION Biofouling has always been a concern in industrial water and process systems. Increased pumping rates, reduced heat transfer and heat rejection rates, higher energy consumption, malodors, dermatological effects and materials of construction corrosion represent a number of the industrial concerns. Recently there has been a shift in the industry to address biofouling from the standpoint of . Microbiocidal efficacies on sessile rather than planktonic microflora, thus reducing the overall biomass present in the biofilm, - Synergistic combinations of multiple microbiocides or use of biodispersants in conjunction with a microbiocide, to achieve lower mass loading of chemicals at higher efficacies, again reducing the overall biomass present in the biofilm. . Utilizing enzymes (5-200 mg/1)2to dissolve the extra cellular polymer through oxidation or hydrolysis. . Utilizing surfactants (20-100 mg/1)3?4?5to condition the surfaces, making the subject surface less prone to adhesion of organic and microbial contaminants. The adhesion of microbial matter can be minimized between a critical surface tension range of 20 to 30 dynes per square centimeter. . Use of increased velocity with the addition of a biocide or a dispersant.6 . Optimization of biofilm control additives sequencing to achieve lower mass loading of ,chemicals while increasing the recovery time of the biofilm.? In some cases, the laboratory experiments were performed utilizing their own testing protocol which was not able to stimulate; . the engineering used in the field for system design. - insitu sessile reduction from heat transfer surfaces, but rather explored sessile bacteria extracted from passive surfaces. - heterogenetic biofilms generated from actual flowing system waters. Investigations were of broths of a few bacteria apparently identified in an industrial system water or fluid. . other inorganic and organic materials inclusion in the fouling biofilm test matrix.
Such investigations could lead to the generation of a comparative study on synergistic dual biocides and synergistic biodispersants which may not provide the most effective approach. This is illustrated in Table 1 whereby the extracted sessile bacteria are in colony forming units per gram dry weight per square centimeter (CFU/g/cm2) from non heated surfaces. The planktonic bacteria counts are reported in colony forming units per milliliter (CFU/ml) of system water and the microflora obtained from the field is also defined under bacterial distribution. It can be seen that all approaches appear to work, Note that, however, upon making an economic review, it is revealed that Isothiazolone and Dispersant D are the most cost effective. Furthermore, a trial was run in the field on a mild steel heat transfer monitoring rod. The results illustrate (Figure 1)that the biofilm recovered in 28-36 hours, and this film had an average fouling factor of 350 to 400x 10-5hr F ft.2/Btu. This performance was deemed unacceptable. The cost of every day and a half addition was much greater than originally calculated at a three day frequency and a two and a half day retention time in the system. A se
ABSTRACT A variety of hydrogen fluoride containing gases, hydrofluonc acid condensates and hydrofluoric acid aqueous solutions are encountered in petrochemical and chemical process applications. A special laboratory test system has been designed to develop stress corrosion cracking and general corrosion data for several nickel alloys in hydrogen fluoride and hydrofluoric acid environments at temperatures from 50°C to 450°C. Test results from this system and aqueous corrosion test results show Ni-Cu alloy 400 (UNS N04400) to be one of the best materials for high temperature applications and better than the ten other nickel base alloys examined in this study for resistance to general corrosion in aqueous hydrofluoric acid.
INTRODUCTION Both hydrofluoric acid (HF) in concentrations up to 70% and anhydrous hydrogen fluoride (AHF) are used in a wide range of applications. Hydrofluoric acid is used for metal pickling, acid treatment of oil wells, glass etching and many other applications. The largest applications for AHF are as an alkylation catalyst for gasoline and in the manufacture of chlorofluorocarbon refrigerants and propellants?. In these processes HF may be present as liquid hydrofluoric acid, vapor above the liquid or as a gas, and temperatures may range from ambient to 650°C(12000F) or higher. Under this wide range of conditions various metals may be resistant to attack or suffer from corrosive attack by either general wastage or stress corrosion cracking (SCC).
Nickel alloys have useful resistance to attack in many HF environments and are often superior to other metals or alloys. Commercially pure Nickel 200 (UNS N02200) is resistant to HF acid at relatively low temperatures, while MONEL* alloy 400 (UNS N04400) has been used for all concentrations to temperatures of about 120°C(2500F). Unfortunately alloy 400 is susceptible to SCC in hydrofluoric acid vapors2. INCONEL* alloy 600 (UNS N06600) has been used successfully in dilute HF acid solutions and in high temperature AHF environments. Other more highly alloyed nickel alloys have been used for HF and AHF service but often do not provide greatly improved corrosion resistance and are much more expensive than the traditional alloys above.
Unfortunately there are only limited data available for comparison of the many nickel alloys available in a variety of HF and AHF environments. This study was undertaken to both develop new data in low temperature aqueous or condensing conditions and high temperature gaseous environments and to compare existing data for various nickel alloys.
ABSTRACT Foreign and domestic test and research reactor fuel is currently being shipped from locations over the world for storage in water filled basins at the Savannah River Site (SRS). The fuel was provided to many of the foreign countries as a part of the Atoms for Peace program in the early 1950?s. In support of the wet storage of this fuel at the research reactor sites and at SRS, corrosion surveillance programs have been initiated. The International Atomic Energy Agency (IAEA) established a Coordinated Research Program (CRP) in 1996 on Corrosion of Research Reactor Aluminum-Clad Spent Fuel in Water and scientists from ten countries worldwide were invited to participate. This paper presents a detailed discussion of the IAEA sponsored CRP and provides the updated results from corrosion surveillance activities at SRS.
In May 1998, a number of news articles around the world reported stories that microbiologically influenced corrosion (MIC) was active on the aluminum-clad spent fuel stored in the Receiving Basin for Offsite Fuels (RBOF) at SRS. This assessment was found to be in error with details presented in this paper. A biofilm was found on aluminum coupons, but resulted in no corrosion. Cracks seen on the surface were not caused by corrosion, but by stresses from the volume expansion of the oxide formed during pre-conditioning autoclaving. There has been no pitting caused by MIC or any other corrosion mechanism seen in the RBOF basin since initiation of the SRS Corrosion Surveillance Program in 1993.
INTRODUCTION Foreign and domestic test and research reactor fuel is currently being shipped from locations over the world for storage in water filled basins at the Savannah River Site (SRS). The fuel was provided to many of the foreign countries as a part of the Atoms for Peace program in the early 1950?s. Now, as part of the U.S, Department of Energy 's non-proliferation policy on foreign research reactor spent nuclear fuel, much of this fuel is coming back from research and test reactors in Europe, Asia, and Latin America. This fuel has been in water storage at the reactor sites for times ranging from a few years to over 40 years, The majority of fuel is manufactured horn uranium-aluminum alloy and is clad with aluminum. The quality of water in the fuel storage basins ranges from highly deionized to untreated and circulated water. In these extreme environments, the aluminum-clad fuel is very susceptible to pitting corrosion. In the early 1990?s corrosion of this aluminum-clad fuel was an issue at several of the storage basins in the U.S. and has been seen on Materials Test Reactor (MTR) type foreign research reactor fuel scheduled for shipment back to SRS. ]
In late 1989, processing of aluminum clad production fuel was suspended at SRS for safety upgrades to the canyon reprocessing facilities and issues related to U.S. non-proliferation concerns. The irradiated fuel and target materials were caught in back end of the nuclear pipeline with no plans for processing imminent. Normal water storage times of 9-18 months soon became years. With less than optimum water quality during the early 1990?s, pitting corrosion of the fuel became an issue at SRS and at other Department of Energy sites.2 An expansive program was initiated at SRS to clean up the water storage basins and to install new and improved water purification equipment. As a part of these activities, a corrosion surveillance program was started at SRS to monitor corrosion of the fuel stored in the basins and to measure the effectiveness of the cleanup activities. Results of these surveillance activities through 1997 have been reported in previous NACE publications.3-5
ABSTRACT This paper reports results of a study comparing the characteristics of mineral scale formation (BaSOA) in a bulk solution and at a solid surface. An electrochemically-based technique, in which the scale was formed on a rotating disk electrode has been used in conjunction with assessment of bulk precipitation measurement. Results from this study have shown that the action of a commercial PolyPhosphinoCarboxylic Acid inhibitor is different in the bulk solution and at the surface. The addition of 25 ppm PPCA, although effective in retarding bulk precipitate formation, enhances the level of surface scaling. Practical implications resulting from these findings are discussed.
INTRODUCTION One of the major recognized problems in the offshore oilfield production industry is the formation of mineral scale on the surface of production equipment and in the pores of rock. 1>2The deposition of various types of scale in oil and gas production operations is very common ; these mainly include calcium carbonate, barium sulfate, calcium sulfate and strontium sulfate.374One of the primary causes of sulfate scale formation is the mixing of two or more incompatible waters. Many of the brines found in the offshore reservoirs contain high concentrations of Ba++ or Sr++. During secondary oil recovery, seawater containing SO~- ions is injected into the reservoir to maintain the pressure. When the waters come into contact in the region of the well bore, a solid precipitate can formi2 the consequences of which range from reduced heat transfer efficiency, increased instabilities in the flow regime, blocked pipes and material damage. This can be accentuated by corrosion occurring in 1conjunction with scaling.? Depending on the local conditions such as temperature, pressure and pH,l scale deposit can be found in, many parts of the production system and on a range of equipment as well as in the near well bore region inside the formation. The low volubility of barium sulfate in almost all! solvents (2rn3/L in water at 20°C), compared with the other scale-forming minerals, make it highly~ undesirable since it cannot be dissolved economically with chemical agents. An expensive solution to the problem of scale formation is to reduce the salt concentration in~ the process water by reverse osmosis prior to injection.7 However, a far cheaper alternative is to use! scale control inhibitors, with the objective of either preventing the mineral scale from forming, o? altering the precipitate to such an extent that it no longer poses a problem. Many classes of chemicals~ !have been identified as scale control inhibitors : organic phosphonates and sulfonated, carboxylated and phosphonated polymers.
Although the formation of, scale on the surface of process equipment (e.g. separation vessels) presents a major problem in the oil and gas industry, by far the majority of studies to date have concentrated on the nucleation and precipitation of scale in bulk solution by traditional chemistry techniques. The relationship between precipitation in the bulk solution and deposition at a solid surface is only partially understood.9 Some recent studies have used tube blocking rigs to address issues relating to surface scale formation and to test inhibitor efficiency.
In previous papers,12 the authors have introduced a new approach to the study of scale deposition on metal surfaces in the absence and presence of scale control. An electrochemical technique! has been devised, which allows the extent of scale to be determined by following the diffusion OF oxygen to the solid surface. Results on calcium carbonate bulk precipitation and surface deposition? have been reported to date. In the work presented herein, the electr
ABSTRACT Coil tube steam generators are low water volume to boiler horsepower (bhp) rating, rapid steaming units which occupy substantially less space per boiler horsepower than equivalent conventional tire tube and water tube boilers. These units can be retrofitted into existing steam systems with relative ease and are more efficient than the generators they replace. During the early ?70?s they became a popular choice for steam generation in commercial, institutional and light to medium industrial applications. Although these boiler designs do not require skilled or certified operators, an appreciation for a number of the operational conditions that result in lower unscheduled maintenance, increased reliability and availability cycles would be beneficial to facility owners, managers, and operators. Conditions which afford lower operating and maintenance costs will be discussed from a practical point of view. An overview of boiler design and operation is also included. Pitfalls are provided for operational and idle conditions. Water treatment application, as well as steam system operations not conducive to maintaining long term system integrity; with resolutions, will be addressed.
INTRODUCTION Coil tube steam generators were originally designed for comfort heating of railway passenger cars and for marine shore side dockage conditions. They later progressed from portable steam cleaning processes to down hole water flood applications. The latter design is of atypical nature, high pressure, and does not provide the required steam quality for steam condensate handling systems. Quick availability of steam and rapid steam production capability is associated with the forced circulation design, low heating surface area and high heat input rates. From the perspective of the coiled heat exchange surface in steam generation, these units could be considered as a highly saturated once through design that produce steam qualities of 99.9%. Over the years many manufacturers have entered the coil tube market, however, approximately five remain today. Configurations from one manufacturer to the next vary as they compete for floor space efficiency, a competitive price and a reliable design.
ABSTRACT Advances in information technology (IT) and in particularly with respect to database systems, have allowed the development of specialized corrosion management systems. Until recently corrosion management and inspection management systems were confined to stand-alone applications on individual PCs with different software packages used for different data types (inspection results, inspection planning, corrosion monitoring, cathodic protection, etc).
More recently fully integrated database systems have been developed and implemented providing all the different aspects of a company wide operation, covering; asset registry, monitored data, inspection planning, maintenance and operational aspects, to be accessed from one application across the company network.
This paper describes the complex data handling requirements of an integrated corrosion management database system ? as used for oil & gas production. Various aspects are already in use in operating companies from the North Sea to the Middle East to the Pacific Rim. As well as current systems the next wave of applications & features (which are already under developments) are also highlighted.
INTRODUCTION What is Corrosion Management? ] Corrosion Management can be defined as that part of the overall management system concerned with development, implementation, review and maintenance of the corrosion policy often causes problems for organizations. This is because complex decisions are required from non- specialist engineers (design, operation and maintenance) who are responsible not only for the day- to-day input of data and information but also for the decision making and future remedial action. They have therefore to place a high reliance on agreed procedures and criteria as part of an operational management system.
The corrosion policy adopted should include establishment of organizational structures with defined responsibilities, reporting routes, practices, procedures, processes and resources. This requires the demonstration of responsibility and accountability for corrosion performance, managing risks, reducing costs, measuring compliance and motivating personnel. A computerized corrosion management system should therefore have the capability to provide the necessary information to allow protection of the assets and hence maximize safety and minimize environmental impact of activities. It should also provide a management tool with which to monitor and control the daily activities of the work force.
ABSTRACT The Society of Chemical Engineers, Japan (SCEJ), and The Japan Petroleum Institute (JPI) have jointly surveyed the experience of so called Chloride-SCC resistant stainless steels in petrochemical plants and refinery plants. The survey covered more than one hundred cases of applications of duplex stainless steels, 400 series stainless steels, high nickel alloys and austenitic stainless steels. The survey included the followings : First, countermeasures taken in advance of or after the occurrence of the damage. Second, environmental conditions of the equipment considered. And third, performance of the adopted countermeasure materials. As a conclusion, detailed analysis has clarified safe limits of SCC resistant alloys, some unexpected weak points, and remarkable performances.
INTRODUCTION Chloride stress corrosion cracking (Cl- - SCC) is a major corrosion problem repeated in various fields of industry. Therefore, various measures to counter SCC have been considered from viewpoints of materials, structure, operation and maintenance. In order to search materials-based countermeasures to SCC, The Society of Chemical Engineers, Japan (SCEJ), in alliance with The Japan Petroleum Institute (JPI), carried out a questionnaire survey of the Cl- - SCC damage and its materials-based countermeasures in the domestic process plants.
The main reason why this survey was carried out is that many Cl- - SCC resistant stainless steels have been developed by steel makers for many years, but details of the adoption of those materials and the resultant performance are not clearly and totally reported. Furthermore, materials were developed mainly under certain laboratory conditions, therefore accelerated laboratory tests should be confirmed by field performance. Some developed materials have good SCC resistance, while miss or do not attain the adequate resistance to other damage, such as localized corrosion and hydrogen embrittlement.
The Corrosion Subcommittee of The Plant Materials Engineering Committee of SCEJ has carried out field surveys of SCC of stainless steel heat exchangersl?2?3, and proposed some countermeasure guidelines to prevent SCC. Based on these surveys, this survey was carried out to confirm the field performance of the Cl- - SCC resistant alloys. The questionnaire survey was made by The Corrosion Subcommittee of SCEJ, in alliance with The Materials Subcommittee of JPI.
The survey is mainly intended to, 1) identify the environmental conditions where Cl- - SCC occurred, and 2 confirm the usage and performance of countermeasure (alternative) Cl- - SCC resistant alloys. As a result of the survey, it was recognized that 316SS, duplex SS, high purity ferritic SS and high alloys are adopted as Cl- - SCC resistant materials. Furthermore, environmental safe limits of those materials as well as unexpected weak points were confirmed. Based on those results, materials selection guidelines to prevent Cl- SCC were obtained.