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Corrosion inhibition and management (including H2S and CO2)
ABSTRACT: As oil and gas becomes more difficult to find and wells are drilled deeper the well bottom hole temperature increases. The temperatures of deep wells can be as high as 230°C. There are a limited number of oil soluble corrosion inhibitors that work well in such systems. In this paper we report the development of a new water based corrosion inhibitor that works at high temperature and can be injected using a capillary string. A new water soluble corrosion inhibitor has many advantages such as greater partitioning in the water phase, higher flash point and higher reportable quantities (RQ) if a spill occurs than the oil soluble counterparts. In this paper the laboratory studies on new high temperature water soluble corrosion inhibitor are reported. The performance of this corrosion inhibitor in a field trial is also reported. Wherever possible the water soluble corrosion inhibitor will be compared with a standard high temperature oil soluble corrosion inhibitor. INTRODUCTION: As shallow onshore and offshore oil fields mature, new discoveries will occur in deeper reservoirs with higher temperatures and more severe materials problems. The challenges presented by ultra high pressure and temperature wells (ultra-HPHT) has been described by Zeringue.1 As described in the article, there are several material issues that are involved in ultra-HPHT well technology. There are both technical concerns and lead time concerns involving the use of nickel based alloys for this application.1 Carbon steel in conjunction with corrosion inhibitors has been used in several wells above 150 °C.2-5 The inhibitors used in these applications were formulated in a hydrocarbon solvent system. An inhibitor that is primarily formulated in water will transport more easily to low spots in the line and preferentially partition to the water phase. The water based corrosion inhibitor will also have a higher flash point and hence be safer to handle. In this paper the development of water based corrosion inhibitors that have similar/better corrosion inhibition performance to a standard high temperature corrosion inhibitor formulated in a hydrocarbon solvent, with superior secondary properties, and environmental and handling advantages is described. EXPERIMENTAL: Corrosion inhibitor tests were performed in a variety of devices to ensure that the corrosion inhibitors are compared in a large number of situations with different ways that corrosive fluids contact carbon steel. The test methodologies included, the wheel bomb (WB), the high speed autoclave (HSAT) apparatus, and the jet impingement (JI) device. The first set of WB tests measured the film persistency of the corrosion inhibitor. In this test 1018 carbon steel coupons were filmed with corrosion inhibitor at different concentration of inhibitors in soda bottles under saturated CO2 and 180 °F (82 °C) conditions for 1 hour. The coupons were then rinsed with deionized water and transferred to the wheel bomb in inhibitorfree brine. The tests were performed at 350 °F (177 °C). The tests were performed with carbon dioxide gas at a pressure of 100 psi (687 kPa). The composition of brine used in the test is shown in Table 1.
- Water & Waste Management > Water Management > Water & Sanitation Products (1.00)
- Materials > Chemicals > Specialty Chemicals (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
ABSTRACT: Commercial alloy tube components from a biomass gasifier were removed and characterized to quantify the extent of corrosion. The Fe- and Ni-base outer bed tubes exposed to the fluidized bed of the gasifier had a metal temperature of ~700°C. Oxalic acid etching suggested that all of the bed tubes were internally carburized. However, evidence of grain boundary carbides or sigma phase was not apparent using electron microprobe. Both chromiaand alumina-forming shield tubes were placed inside the bed tubes to shield the combustion flame from overheating the bed tubes. These tubes were exposed to a much higher temperature oxidizing environment. As expected, the alumina-forming shield tube material showed less degradation. However, the Al depletion profiles were much higher than typically observed in laboratory tests. Compared to laboratory exposures of the chromia-forming shield tube alloy, the Cr depletion profiles measured in the shield tube suggest that the metal temperature was much lower than 1100°C. INTRODUCTION: In the pulping process for papermaking, black liquor is a waste stream containing the unused portion of the wood and the remaining inorganic process compounds. Black liquor gasification1 is a potentially higher efficiency, lower cost and lower emission alternative to a recovery boiler, which traditionally is used to regenerate the pulping chemicals (e.g. NaOH and Na2S). One gasification method uses steam reforming in a fluidized bed and is attractive because it uses relatively low temperatures (£ 605°C) to keep the alkali salts below their melting points.2 This process was demonstrated in full scale facilities at mills in Virginia and Ontario. Both of these plants use the semi-chemical sodium carbonate paper-making process, which In this lower-temperature process, heat is transferred to the bed through pulsed heater modules, which consist of ~250, “bed” tubes which are ~3m (10') long and contain the hot combustion gases. Combustion occurs in a refractory lined chamber which burns product gas or auxiliary fuel in a pulsed mode producing gas temperatures of ~1300°C. To prevent the bed tubes from exceeding 605°C, a ~60cm (2') long “shield” tube is used inside each outer bed tube. Thus, the outside of the bed tubes are exposed to the bed environment and can experience both corrosion and erosion. On the inside, the bed tubes are exposed to the higher temperature combustion gas containing O2, H2O, COx, uncombusted fuel and possible contaminants from the fuel. The first alloys selected for this application were type 321 stainless steel (321SS or UNS 32100), for the bed tubes and super austenitic alloys 330 (N08330) and 800H (N08811) for the shield tubes.1,3,4 However, with a desired module lifetime of 40kh, more corrosion-resistant alloys are likely required. The 321SS bed tubes were internally carburized in service, thus more heavily alloyed materials were considered to resist this form of attack.4 An aluminide coating5 also was suggested to protect the 321SS tubes. For the higher temperature shield tubes, prior work6 suggested that a chromia-forming alloy with a reactive element7 addition or an aluminaforming alloy would be needed to meet the lifetime goal.
- North America > United States > Virginia (0.24)
- North America > Canada > Ontario (0.24)
- Energy > Oil & Gas > Upstream (0.48)
- Materials > Metals & Mining > Steel (0.35)
- Materials > Paper & Forest Products > Paper Products (0.34)
ABSTRACT: Chloride-based deposits can significantly accelerate the progress of elevated temperature degradation of stainless steels and nickel-base alloys. Such deposits are present in the byproducts of combustion of alternative fuels and are common in the environment experienced by hot automotive exhaust components. A test was developed to investigate the susceptibility of materials to attack under chloride salt deposits at elevated temperatures, using a sample incorporating stressed, unstressed, and welded segments. Both gravimetric and metal recession measurements were used to determine the progression of corrosion. Nickel-base alloys were found to be resistant to deposit-assisted attack, while common stainless steels were prone to scaling and exfoliation. Results will also be presented on recently developed higher-alloy content stainless steels which exhibit corrosion resistance similar to that of the nickel-base superalloys, and on lean austenitic stainless alloys intended as replacements for traditional austenitic stainless steels. INTRODUCTION: Alloys used at elevated temperatures rely on the formation of a slow-growing, persistent, adherent oxide scale, generally referred to as a protective oxide layer, as protection against excessive attack by high temperature oxidation and corrosion. The majority of heat-resistant alloys available in wrought product forms rely on the selective oxidation of chromium to form a protective chromium oxide scale. Disruption of this scale by mechanical or chemical means can result in rapid degradation of the underlying metal. 1 A protective oxide scale can be disrupted at elevated temperature by the formation of reactive deposits. This is commonly observed in industrial environments where the gas flow stream contains particulate matter or vapor species that can condense on surfaces. Chloride salts are a commonly encountered deposit. Most of these salts melt at temperatures ranging from 600-800°C. 2 When molten, chloride salts can aggressively attack oxide scales - one common industrial use of molten salt baths is in the heattreating and descaling of hot-worked steels and alloys to prepare a clean surface for further use. Extended exposure to molten salt can result in metal wastage and intergranular penetration. 3 When sulfur is present in the gas stream, a more complex form of attack known as active oxidation can occur. This is often observed in systems handling flue gas which contains both entrained chlorides and sulfur-bearing species, notably in the burning of biomass and waste to provide heat for firing boilers. The sulfur-bearing species in the flue gas lower the melting point of the chloride deposits by forming sulfates, setting up a sustaining reaction in the liquid deposits where chlorine is circulated through the deposit to the metal substrate, resulting in the formation of volatile metal chlorides which remove metal from boiler tubes and other metallic components. 4 Similar reactions between ingested salts and sulfurbearing species lead to hot corrosion of alloys used typically in gas turbines. 5 Underbody exhaust components for automobiles typically operate at temperatures below the melting points of common chloride salts in the absence of sulfur-bearing compounds. Salt is deposited on exposed surfaces of components, particularly in cold climates when deicing compounds are used on roads.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (0.88)
ABSTRACT: Testing of discrete titanium-based anodes was initiated in September 2006. The purpose of these tests was to investigate the operating characteristics of three types of discrete anodes installed in reinforced concrete blocks and to determine the relationship between acid formation/damage and operating current. The anodes tested were mixed metal oxide (MMO) catalyzed star-shaped and round configurations installed in two different types of grouts. Test blocks were operated indoors and were ponded to prevent over-drying on a cycle similar to the test procedure used in ASTM Standard Test Method G-109. This paper summarizes appearance, resistance, and voltage data collected over 570 days of operation. Autopsies were conducted on anodes after 235, 404, and 570 days on line. The amounts of Anode Reaction Product (ARP) are presented in the paper, together with pictures. Results were either excellent or good, based on the condition of the grout surrounding the outside surfaces of the anodes. The amount of ARP observed for the anodes was roughly proportional to the operating current density. These test results provide significant information for the application of discrete anodes in the concrete rehabilitation industry. INTRODUCTION: The concrete repair industry is developing in the western countries where it's needed to extend the service life of dated infrastructures and to preserve buildings of architectural importance or in the Middle East where the concrete is exposed to hot and aggressive environmental conditions. Impressed Current Cathodic protection (ICCP) is widely used in the rehabilitation of concrete structures and is now recognized as a cost effective and reliable technique to stop rebar corrosion and extend the service life of reinforced concrete structures exposed to the atmosphere. During the 1980's new anode types were developed, first as polymer-based anodes and then with MMO-activated titanium and finally conductive paints (carbon filled). The most successful anodes for bridge decks are titanium based with mixed metal oxide coatings, either as ribbon in slots or as mesh under an overlay1. The same anodes have also been applied to bridge substructures, parking garages, wharves, buildings, floating foundation slabs, and cooling towers. There were two important breakthroughs in anode design that made CP design more flexible and applicable to new and historic structures2. The first one was the mixed metal oxide coated titanium mesh ribbon that made possible the optimization of the current protection in the different zones of the structure depending on the steel density and environmental conditions. This invention was widely applied to new structures where lower protection current is required to prevent initiation of corrosion in aggressive high chloride environments. The other was the development of probe anode rods of various configurations that could be inserted in small holes drilled unobtrusively in the structure. In 2005 Industrie De Nora S.p.A.(1) filed a patent application3 for a discrete anode for cathodic protection of reinforced concrete where it is described a cathodic protection system of reinforced concrete structures with discrete anodes obtained starting with a corrugated planar substrate welded to a longitudinal current collector.
- North America > United States (0.68)
- Europe (0.48)
- Materials > Construction Materials (1.00)
- Construction & Engineering (1.00)
- Energy > Oil & Gas > Upstream (0.48)
Update Results Of Zno Behavior As A Corrosion Inhibitor For Rebars
Rincón, Oladis T. (Centro de Estudios de Corrosión, Facultad de Ingeniería, Universidad del Zulia) | Sánchez, Miguel (Centro de Estudios de Corrosión, Facultad de Ingeniería, Universidad del Zulia) | Millano, Valentina (Centro de Estudios de Corrosión, Facultad de Ingeniería, Universidad del Zulia) | Pérez, Orlando (Centro de Estudios de Corrosión, Facultad de Ingeniería, Universidad del Zulia)
INTRODUCTION: ABSTRACT: In this paper, studies were conducted in a concrete structure built twenty years ago, approximately, which due to the aggressive atmosphere of exposure (Progreso Port in Mexico), led to their deterioration during an early age. The latest repair (over 4 years ago) was conducted with a partial replacement of concrete which contains different concentrations of inhibitors: 4% zinc oxide (ZnO), 4% of calcium nitrite (Ca (NO2)2), and 4% of mixture (2% ZnO + 2% Ca (NO2)2), in addition to the repair with conventional concrete. Electrochemical behavior of the repairs was done through the linear polarization resistance technique (Rp) and the corrosion potential by a commercial corrosometer. After over four years of exposure, ZnO is the only inhibitor that shows a clear passivation (Ecorr <-200 mV and an icorr of <0.2 µA/cm2). On the other hand, steel piles were evaluated over eight years exposure in a platform located in Lake Maracaibo, Venezuela, lined with concrete in the wave and splash zone. ZnO was added to the concrete in the range of 0.0-3% and the results indicate that only the concrete coating with 1% ZnO performed very well with and without the cathodic protection system installed in the submerge zone. Reinforced steel corrosion is the main problem that diminishes the durability of concrete structures. The use of corrosion inhibitors is an attractive alternative as a way to stop the corrosive attack of agents like the chloride ions, in structures exposed to marine atmospheres as in the case of ports, bridges and dikes; specially, in repairs cases where it is unavoidable the use of aggregates and/or water contaminated with this agent. (1-28) So far, Calcium Nitrite (Ca (NO2)2) is the only inhibitor that has been longer evaluated to justify its commercial use for corrosion control in reinforced concrete. However, it is too expensive and difficult to acquire in some countries and, also, its inhibiting effect can be lost in relations of Cl-/NO2 - > 1(21), which can be present as an effect of the migration/diffusion of Chloride ions inside the concrete matrix and/or the leaching out of the nitrite, due to the water solubility of this compound. One of the most promising compounds that have been studied in the Corrosion Study Center in our university (Centro de Estudios de Corrosion de LUZ), as total or partial substitutes of Calcium Nitrite, is the Zinc Oxide (ZnO)(3, 7, 22-28), as its electrochemical study shows the passivity of reinforced steel in concrete exposed to a very aggressive marine atmosphere. It is known that ZnO acts as a cathodic inhibitor when used in water, since it can precipitate compounds in the cathode due to its high alkalinity compared to the anode. However, concrete possesses a high alkalinity, and it has been determined(28) that Zinc Oxide precipitates compounds on the cathodic and anodic areas. It is expected that zinc oxide as inhibitor reacts in concrete in the same way as the zinc oxide on a galvanized steel bar does, in the following way.
- North America > Mexico (0.49)
- North America > United States > Texas (0.29)
- South America > Venezuela > Zulia > Maracaibo (0.26)
- Materials > Chemicals > Commodity Chemicals (1.00)
- Materials > Chemicals > Specialty Chemicals (0.71)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
INTRODUCTION: ABSTRACT : Risk Based Inspection (RBI) results using the API RBI software are presented for calculating a risk value for each piece of plant fixed-equipment. Usually RBI implementation results in fixed-equipment inspection program modification. Inspection is specified for equipment items that exceed Owner acceptable risk criteria while it is waived for equipment that is below acceptable risk levels. In RBI analysis, equipment risk value consists of a Likelihood-of-Failure (LOF) and a Consequence-of-Failure (COF) element. The sum of different equipment damage mechanisms (internal corrosion, external corrosion, cracking mechanisms and mechanical damage) is the LOF value. The COF value is the sum of the damage to the specific equipment item, damage to surrounding equipment, lost production, serious injury to personnel and environmental clean-up. This paper describes benefits realized from applying RBI in gas plants as a reliability-engineering tool for guiding decisions in optimizing fixed-equipment mechanical integrity. Utilizing the calculated LOF, COF and Risk values for each piece of fixed-equipment allows for extracting maximum value from a RBI database. Based on RBI calculated risk values, fixed-equipment relative risk ranking is established to: -set priorities and focus attention on the critical areas -justify capital investment for Lifetime Extension projects -proactively address Loss of Primary Containment and Process Safety issues . RBI is a well established methodology within the oil & gas industry that delivers bottom-line improvement results. The RBI analysis focuses only on fixed process equipment (vessels and piping). RBI can successfully replace the time-based criteria for inspection activities that have been used across industry facilities in the past. The RBI methodology consists of a detailed inspection, corrosion, materials and process analysis that aims to identify equipment risk and propose a risk-prioritized inspection plan for optimized equipment maintenance. Prescriptive industry practices are the traditional approach for in-service fixed equipment inspection. The American Petroleum Institute (API) recommended inspection codes for vessels (API-510), for piping (API-570) and for tanks (API-653) basically suggest a five to ten year interval between inspections if RBI methodology is not used. In RBI analysis the relative equipment risk value determines the inspection plan. High-risk equipment becomes the focus of our finite inspection resources. Equipment risk is defined as the product of Likelihood of Failure (LOF) and Consequence of Failure (COF). In a risk-based approach, inspections provide updated prediction as to whether corrosion degradation is anticipated and the extent of equipment damage that is expected. Recognizing the potential for failure and specifying the right inspection method at the proper equipment location results in a reduction of TDF. The underlying implicit statement is that in a competent organization inspection findings will be followed by proper action that will actually reduce TDF and therefore equipment risk. An action plan may include one or a combination of the following activities: follow-up inspection, equipment monitoring, use of upgraded materials, replacement, operational procedure changes. Consequence of failure is not impacted from inspection since loss of containment will have the same consequences regardless of inspection activity. However, improvements in detection, isolation and mitigation systems will reduce potential consequence.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Management > Risk Management and Decision-Making (1.00)
- (3 more...)
ABSTRACT: This study applied a pH buffer as a corrosion inhibitor in brine packer fluids. The study systematically evaluated the effect of pH buffer on corrosion control of steel materials at elevated temperatures up to 425oF. The paper describes laboratory results of pH buffer in sodium chloride, potassium chloride, sodium bromide and sodium chloride/sodium bromide brines and field case histories for buffered brine packer fluids in high-temperature high-pressure wells. The pH buffer applied is cost effective, readily available and easily handled and monitored in the field. Results from buffer capacity, general corrosion and stress corrosion cracking tests are presented. Field case histories are presented to demonstrate the successful use of the pH buffer in brine packer fluids at high temperatures. INTRODUCTION: Sodium, potassium and calcium chloride and sodium, calcium and zinc bromide brines have been successfully used for well completions for more than 25 years. More recently, sodium, potassium and cesium formate brines are being explored for use as completion and packer fluids. These brines can be applied as single-, two- or three-salt mixtures based on density, crystallization temperature, and economic requirements. However, brine corrosivity is a major concern - especially when the brines are used as packer fluids (which remain in contact with production tubing and casing for an extended period of time). Generally, brine corrosivity increases with increases in temperature, brine density and zinc content. The corrosivity of brines also increases with a decrease in pH of brine solutions. In application, single-salt brines have density limitations, and mixtures of two or more salts are needed to provide adequate density for hydrostatic pressure requirements. In most cases, mixtures of salts are more corrosive than single-salt brines. Some single-salt brines have lower corrosion rates than others. Due to the corrosive nature of brines, a corrosion inhibitor becomes necessary to reduce corrosivity. Two types of inhibitors are conventionally used: film-forming amine and low molecular weight inorganic thiocyanate (SCN-) compounds. In application, thiocyanate corrosion inhibitors have unique characteristics compared with conventional amine-based inhibitors: excellent solubility in high-density brines and ability to control corrosion of brines on carbon steels and low alloy steels at high temperatures. Thiocyanate inhibitors were originally developed to control corrosion of carbon steels in ZnBr2 brines and also found application in non-zinc brines such as sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2), sodium bromide (NaBr) and calcium bromide (CaBr2). Thiocyanate inhibitors for oilfield corrosion control include sodium thiocyanate (NaSCN), potassium thiocyanate (KSCN) and ammonium thiocyanate (NH4SCN). However, when applied at high temperatures, thiocyanate can decompose and yield hydrogen sulfide (H2S) or free sulfur. Burke et al.1 reported that NaSCN present in NaBr brines decomposes at temperatures above 302oF and forms hydrogen sulfide. Hydrogen sulfide certainly increases the potential of sulfide stress corrosion cracking (SSC) of steel materials. Isaacs et al.2 also reported that thiocyanate can form elemental sulfur and cause SCC of austenitic stainless steels. Ke et al.3 further reported that thermal decomposition of thiocyanate can induce sulfide stress cracking.
- Well Completion (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Health, Safety, Environment & Sustainability (1.00)
Performance Of Corrosion Prevention Methods-18 Year Study
Kessler, Richard J. (Florida Dept of Transportation-Corrosion Research Laboratory) | Powers, Rodney G. (Florida Dept of Transportation-Corrosion Research Laboratory) | Paredes, Mario A. (Florida Dept of Transportation-Corrosion Research Laboratory)
ABSTRACT: Over the last 30 years, a variety of approaches have been taken to delay the start of corrosion of reinforcement in concrete. While short term and accelerated performance data is readily available in the literature, it is difficult to find long term laboratory data performed under control conditions. This report intends on filling that gap in the knowledge base of the performance of the various products evaluated. The long term laboratory performance of specimens with 1.75 inches (4.4 cm) of concrete cover exposed to 3 wt% NaCl at 72° F (22 °C) and 64% humidity is presented. Specimens were made with corrosion inhibitors, concrete penetrant sealers, coated rebar, galvanized rebar, and supplementary cementitious materials of various types and quantities. INTRODUCTION: In the late 1980's the Florida Department of Transportation (FDOT) identified the need for a study investigating the performance of all corrosion prevention systems available at that time. The basic cause of corrosion was already known to be the chloride ion1, and the majority of the prevention systems deal with ways to prevent chloride ions from reaching the steel, either by blocking it, slowing it down, or rendering the steel bar immune. The basic approaches can be grouped in the following five general areas: 1. Concrete Sealer: Intended to block the passage of water and chloride ions into the concrete. Penetrant sealers like Silane and Siloxane fall in this category. 2. Rebar Sealer: Intended to block the chloride ions that have penetrated the concrete from reaching the surface of the steel. Epoxy coatings fall in this category as well as inorganic polymer coatings. 3. Densifier: Intended to slow down the ingress of chloride ions to such a degree that corrosion would not affect the designed service life of the structure. Pozzolans like fly ash and silica fume are part of this category. 4. Sacrificial Metal: Intended to protect the metal even in the presence of chloride ions by use of an anodic sacrificial metal. Zinc galvanizing is an example of this approach. 5. Corrosion Inhibitor: Intended to extend the passivation region of the steel even in the presence of chloride ions. Calcium nitrite is an example of corrosion inhibitors. EXPERIMENTAL PROCEDURE: Project Description For discussion purposes, the mixes will be divided into three groups. The first group consisted of the first thirteen mixes. Two of these mixes were eliminated; one due to mixing complications (Mix # 6, polymer modified), and the other due to the high cost of materials (Mix # 12, stainless steel) which was not believed to be cost effective for actual use. The cement content was maintained constant for all these mixes except for Mix 13 where fly ash was used as a cement replacement, silica fume (SF) was used as an addition. The second group consisted of Mixes 14 to 24. During the casting of these mixes, no single variable was held constant. Concrete was made following the supplier's recommendations or in combinations attempting to optimize performance.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- (2 more...)
Synthesis And Characterization Of Nickel-Alumina Dispersion Strengthened Composite By Electrodeposition Method
Aole, Dhanashree (Engineering Research Center, Tata Motors Ltd) | Bhadauria, Pallav (Engineering Research Center, Tata Motors Ltd) | Hariharan, V. (Engineering Research Center, Tata Motors Ltd)
ABSTRACT: Dispersion strengthened Nickel- alumina composite was fabricated by electro-deposition method on a non-metallic substrate with the help of nickel-sulphamate bath. The fine particles of alumina were dispersed and vigorously stirred in the bath in order to get uniformly into the Ni-matrix. The influencing parameters i.e. current density, pH, and temperature of the electrolyte were varied to study the effect on the composite quality. The Ni-alumina dispersion strengthened composite was fabricated by optimizing the parameters like current density, temperature, pH of the electrolyte etc. of the sulphamate bath. The composite coatings were characterized pertaining to physical appearance, microstructure, hardness and thickness. The obtained results indicate that the micro-structural refinement of the Ni- matrix and uniformity of distribution of oxide particles is obtained by choosing the small size of (less than 5 µm) particles. Also the results indicate increase in the hardness of the Ni-matrix after dispersion of the oxide particles. INTRODUCTION: There is a growing interest in extending the quality and reliability of artifacts in mechanical systems. This has led to the development of new materials and coatings which can withstand the severe conditions during service. If a monolithic material is unsuitable for a particular application, composite materials and structures are considered. Such composite structures include coatings and surface modified materials. One of the main aims of surface engineering is to improve properties such as resistance to friction, wear, corrosion, fatigue and biocompatibility. One purpose of surface engineering is to use a cheaper material as a substrate and a rare or expensive material as a coating. There are many methods in which surface can be modified to improve its performance. This includes traditional methods like carburizing, flame hardening etc. Electro and electroless deposited coating, and new methods including physical vapor deposition, chemical vapor deposition, ion implantation and laser processing. Nickel coatings are obtained on substrates of steels, brass, zinc and other metals in order to provide a surface that is resistant to corrosion, erosion and abrasive wear. A more recent application of the co-deposition of fine non-conducting particles has been for decorative purposes; the list of the materials used is about the same as mentioned above, and their size ranges from 0.2 to 0.5 µm. Co-deposition of non-conducting particles with nickel has been used to improve its wear and abrasion resistance; diamond powders have been co-deposited for use in abrasive tools. Nickel has been dispersion hardened by the co-deposition of 2-6% (by volume) of very fine particles of Alumina. The electro-deposition solutions are of different types such as watt's bath, chloride bath, nickel fluoborate bath etc. Of all these, nickel sulphamate bath is best suitable in terms of the throwing power(1). However, conventionally methods used to make composite coatings included high initial setup cost and highly skilled laborers. The fabrication methods used were good for obtaining thin coatings only. Residual stresses were built up in the coatings due to high temperature involved that were difficult to manage, thus require additional annealing treatment.
- Materials > Chemicals (0.94)
- Materials > Metals & Mining (0.68)
ABSTRACT: This study consists of introducing a new method that may be used to globally quantify the performance of a corrosion inhibitor in a laboratory testing program. For a given corrosion inhibitor, the new concept introduces and defines a single indicator called the Global Performance Index (GPI) that simultaneously takes into account all the corrosion rate measurements from the various techniques applied in the lab in order to assess the performance of the inhibitor for a given application. The index is dimensionless, ranges between 0 and 1 and can account for both general and pitting corrosion rates in a systematic fashion. It also lumps the performances of the inhibitor as reported by all the laboratory test methods, which are usually chosen as a function of the field conditions and the nature of the production system. The new method is illustrated in the case of a corrosion inhibitor selection program for a wet gas transport line and an oil export line. It is particularly recommended that the proposed GPI is to be used in comparing and ranking a given set of corrosion inhibitors for a production system of interest. It can also be utilized to assess the performance sensitivity of a chosen corrosion inhibitor as a function of the variability of the operating field conditions. The method can be extended to evaluate the overall performance of any other non produced chemical, such as scale inhibitors, biocides or wax inhibitors in laboratory testing. INTRODUCTION: When corrosion inhibition is chosen as the corrosion mitigation method for a given application, the selection of the corrosion inhibitor as well as its injection rate and mode become a critical component of a successful corrosion control program. The initial screening of corrosion inhibitors is usually performed by the chemical supply companies. Per application, various inhibitors are often provided by the vendors to the users for selection by performing application-specific testing, screening and ranking. Such exercise is tedious, sensitive to the type of tests and complicated by the number of parameters which affect the performance of inhibitors 1,2,3. DESCRIPTION OF THE METHOD: Traditionally, when a corrosion inhibitor selection program is initiated at the laboratory level for a given application, a list of corrosion inhibitors are chosen for qualification and ranking purposes in terms of performance. It is a common practice to simulate as closely as possible the actual field conditions using representative synthetic brine and inhibitor free crude from the field. The test conditions are usually fixed to mimic the worst case corrosive environment which could prevail in the field. Depending on the specificity of the production system, a set of laboratory experiments are chosen to evaluate the corrosion inhibitor performance. In order to assess the corrosivity of the system in the absence of inhibition, the uninhibited corrosion rate is established for each experiment and chosen as a control. The inhibited corrosion rate is then determined for a chosen inhibitor dosage. A typical laboratory experimental data set is shown in table 1.
- Water & Waste Management > Water Management > Water & Sanitation Products (1.00)
- Materials > Chemicals > Specialty Chemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)