Showing papers in "Corrosion in 2006"

Threshold Chloride Concentrations of Selected Corrosion-Resistant Rebar Materials Compared to Carbon Steel

Abstract: The threshold chloride concentration for solid Type 316LN (UNS S31653) stainless steel, Type 316L (UNS S31603) stainless steel clad, 2101 (UNS S32101), Fe-9%Cr, and carbon steel rebar (ordinary ASTM A 615M) was investigated using potentiodynamic and potentiostatic current monitoring techniques in saturated calcium hydroxide (Ca[OH]2) + sodium chloride (NaCl) solutions. There is general consensus in this study and the literature that the chloride threshold for carbon steel is less than a chloride to hydroxl (Cl−/OH−) molar ratio of 1. Solid Type 316LN stainless steel rebar was found to have a much higher chloride threshold (i.e., threshold Cl−/OH− ratio > 20) than carbon steel (0.25 < Cl−/OH−< 0.34). Type 316L stainless steel clad rebar possessed a chloride threshold expressed as a Cl−/OH− ratio of 4.9 when cladding was intact. However, surface preparation, test method, duration of period exposed to a passivating condition prior to the introduction of chloride, and the presence of cladding defects...

Influence of Chromium and Molybdenum on the Corrosion of Nickel Based Alloys

Abstract: The addition of chromium and molybdenum to nickel creates alloys with exceptional corrosion resistance in a diverse range of environments. This study examines the complementary roles of ch...

Corrosion of Austenitic Alloys in Supercritical Water

Abstract: The purpose of this study was to determine the mechanism by which austenitic iron- and nickel-based alloys oxidize in pure supercritical water. Austenitic stainless steel alloys Type 304 (UNS S30400) and Type 316L (UNS S31603) and nickel-based Alloy 625 (UNS N06625) and Alloy 690 (UNS N06690) were exposed in deaerated supercritical water over the temperature range from 400°C to 550°C. Exposure experiments resulted in the formation of a two-layer oxide on Type 304 and Type 316L in which the outer layer is porous magnetite (Fe3O4) and the inner layer is a denser iron-chromium spinel. In Alloy 690 the outer layer is iron-rich and the inner layer is composed of chromia (Cr2O3), nickel oxide (NiO), and Ni(Cr,Fe)2O4. The oxide on Alloy 625 was too thin to measure. Inner and outer oxides have the same grain orientation as the matrix on the stainless alloys, and on Alloy 690, the inner oxide has a common orientation with the matrix but the outer layer consists of randomly oriented oxides. The inner/outer...

Diagnosing Microbiologically Influenced Corrosion: A State-of-the-Art Review

Abstract: Diagnosing microbiologically influenced corrosion (MIC) after it has occurred requires a combination of microbiological, metallurgical, and chemical analyses. MIC investigations have typic...

Assessing the Corrosion Performance of High-Level Nuclear Waste Containers

Abstract: The assessment of the corrosion performance of containers (waste packages) for the disposal of high-level nuclear waste has been underway for more than 20 years. A review of the rationale behind disposal site selection, container design, materials selection for fabrication, and the bases for the development of corrosion models is discussed.

Stress Corrosion Cracking of Carbon Steel in Ethanol

Abstract: This paper presents the results of a study on the effects of water, acetic acid (CH3COOH), oxygen, corrosion inhibitor, chloride, methanol (CH3OH), denaturant, and corrosion product on the stress corrosion cracking (SCC) of steel in ethanol (C2H5OH). The factor that was found to have the greatest effect on causing SCC was corrosion potential, as influenced by oxygen. The lower critical potential for SCC ranges from 25 mV vs. saturated calomel electrode (SCE) to 300 mVSCE, depending on the presence of chloride and methanol as impurities. Galvanic contact with precorroded steel appeared to exacerbate SCC by increasing the corrosion potential. Within the fuel ethanol specification limits, chloride had a less significant effect than oxygen. SCC was intergranular when the chloride concentration in ethanol (both laboratory and field samples) was low (less than 1 ppm) and it was transgranular when the chloride concentration was high (32 mg/L). A denaturant, a corrosion inhibitor, and acidity, within the...

Influence of Carbide Precipitation and Rolling Direction on Intergranular Stress Corrosion Cracking of Austenitic Stainless Steels in Hydrogenated High-Temperature Water

Abstract: The intergranular stress corrosion cracking (IGSCC) growth behavior of austenitic stainless steels (SS) in hydrogenated high-temperature water were studied using compact tension specimens ...

Fundamental Aspects of CO2 Metal Loss Corrosion - Part 1: Mechanism

Abstract: Carbon steel is thermodynamically unstable in water with dissolved CO2 and the only reason that carbon steel is so attractive and can be so widely used in oil and gas production is that the steel surface becomes covered by a protective layer of corrosion products, oil, mineral scale or inhibitors. It is relatively easy to predict and explain the high corrosion rates on bare steel. The real challenge is to reduce the corrosion and that requires knowledge about the performance of the protective layers, means to predict the breakdown of the layers and methods and techniques to ensure that robust layers form on the surface. The paper discusses how CO2 affects the water chemistry, the electrochemical reactions on the bare steel surface, and the initiation and growth of protective corrosion product films. As many sweet systems contain organic acids that affect the solution chemistry and the formation and stability of the FeCO3 corrosion product films, organic acids need also to be considered when the effect of CO2 is discussed.

A Comparison of the Corrosion Behavior of Nanocrystalline and Conventional Al 5083 Samples

Abstract: Pitting scan (PS) and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the corrosion behavior of nanocrystalline (NC) samples and conventional Al 5083 (UNS A95083) in three solutions with different chloride concentrations. The PS obtained in 0.5 N sodium chloride (NaCl) and in 0.5 M sodium sulfate (Na2SO4) + 0.1 N NaCl indicated that pitting should occur in these solutions. These results were confirmed by EIS data that were recorded for up to 25 days. For exposure to 0.5 M Na2SO4 + 0.05 N NaCl the pitting (Epit) and protection (Eprot) potentials determined after exposure for 2 h suggested that pitting would not occur in this solution. However, the initial impedance spectra were indicative of pitting. Tests carried out after exposure for 2 days and 3 days showed passive behavior, but starting with exposure for 5 days, pitting was again indicated for all three samples. PS performed at the end of the EIS tests suggested that this result was due to the increase in corrosi...

The Mechanism of Action of Isothiazolone Biocide

Abstract: Isothiazolone biocides have proven efficacy and performance for microbial control in a variety of industrial water treatment applications. Understanding the mechanism of action of industrial biocides is important in optimizing their use and combating resistance if encountered. Isothiazolones utilize a two-step mechanism involving rapid inhibition (minutes) of growth and metabolism, followed by irreversible cell damage resulting in loss of viability (hours). Cells are inhibited by disruption of the metabolic pathways involving dehydrogenase enzymes. Critical physiological functions are rapidly inhibited in microbes, including growth, respiration (oxygen consumption), and energy generation (adenosine triphosphate synthesis). Cell death results from the destruction of protein thiols and production of free radicals. The rate and extent of killing may be enhanced by various adjuvants including surfactants. This unique mechanism results in a broad spectrum of activity, low use levels, and difficulty in attaining resistance.

Intergranular Stress Corrosion Cracking Behavior of Austenitic Stainless Steels in Hydrogenated High-Temperature Water

Abstract: The influence of material factors on the intergranular stress corrosion cracking (IGSCC) susceptibility of austenitic stainless steels under hydrogenated high-temperature water were studie...

Corrosion of Carbon Steel by H2S in CO2 Containing Oilfield Environments

Abstract: The effect that even small concentrations of H2S can have upon CO2 corrosion has been recognized since at least the 1940's. Early studies showed that the FeS corrosion products that were formed had an impact, but disagreed whether the impact was beneficial or not. Although H2S corrosion has not received the level of attention given to CO2 corrosion, the literature has shown that there are a number of different forms of FeS that can form as corrosion products, depending upon the exposure conditions. Between the corrosion, geochemical and thermodynamics literature, a great deal is known about the corrosion chemistry involved with the formation of the various FeS species as well as the impact that each has upon further corrosion.

Kinetics of Iron Sulfide and Mixed Iron Sulfide/Carbonate Scale Precipitation in CO2/H2S Corrosion

Abstract: Glass cell experiments were conducted to investigate kinetics of iron sulfide and mixed iron sulfide/carbonate scale precipitation in CO2/H2S corrosion. Weight gain/loss (WGL) method was used to investigate the scale formation using X65 carbon steel as substrates. Scanning Electron Microscopy (SEM/EDS), X-ray Diffraction methodology (XRD), X-ray Photoelectron Spectroscopy (XPS), and Electron Probe Micro-analyzer (EPMA) were used to analyse the scale. The experimental results show that the corrosion products formed in CO2/H2S system depend on the competitiveness of iron carbonate and mackinawite. At high H2S concentration and low Fe concentration, mackinawite was the predominant scale formed on the steel surface. At low H2S concentration and high Fe concentration, both iron carbonate and mackinawite form. It was also found that ferrous ions forming mackinawite scale mainly come from Fe released from the steel surface.

Protective Iron Carbonate Films—Part 1: Mechanical Removal in Single-Phase Aqueous Flow

Abstract: The protective role of iron carbonate fi lms deposited on steel surfaces as by-products of carbon dioxide (CO2) corrosion may be hindered by mechanical fi lm removal due to hydrodynamic forces. Damage to the fi lm is frequently accompanied by se- vere corrosive attack, which may ultimately result in costly equipment failure. The present work reports on experimental investigations of mechanical fi lm removal (its kinetics and level of damage to the fi lm) using a rotating cylinder con- fi guration in the highly turbulent fl ow regime. Corrosion rate monitoring using the linear polarization resistance technique was used as a tool for implicit fi lm removal rate measuring, whereas scanning electron microscopy served for verifi cation and evaluation purposes. Two types of fi lms were studied, one less uniform and adherent and the other more compact and adherent. The results clearly show that pure mechani- cal removal in undisturbed single-phase fl ow does occur. However, fi lm removal starts after an initiation period and is only localized. The differences in the thickness, microstruc- ture, and topography of intact and residual fi lms are dis- cussed in detail for both fi lm types. In addition, the possible mechanism of mechanical fi lm removal from the fl uid mechan- ics point of view has been proposed.

Stress Corrosion Cracking of Austenitic Alloys in Supercritical Water

Abstract: The purpose of this study was to determine the stress corrosion cracking behavior of austenitic alloys in pure supercritical water (SCW) and to gain a better understanding of the stress co...

On the interpretation of corrosion processes through the superposition of electrochemical partial processes and on the potential of mixed electrodes

Abstract: EDITOR’S NOTE: This new series, “Classic Paper in Corrosion Science and Engineering,” will feature reprints of defining papers that presented milestone advances in corrosion science and engineering. Each paper will be accompanied by a perspective written by a senior member of the corrosion research community. (Comments may be submitted via e-mail at PubsOnline@mail.nace.org or mailed to Dr. J.B. Lumsden, FNACE, CP SSP TJP O Technical Editor, Rockwell International, 1049 Camino Dos Rios, Thousand Oaks, CA 91360.) —Jesse B. Lumsden, Technical Editor * Corrosion and Environmental Effects Laboratory (CEEL), Department of Materials Science and Engineering, University of Southern California, Los Angeles, CA 90089-0241. E-mail: mansfeld@usc.edu. Classic Paper in Corrosion Science and Engineering with a Perspective by F. Mansfeld

An 18-Year Exposure Test of Thermal-Sprayed Zn, Al, and Zn-Al Coatings in Marine Environment

Abstract: The thermal spray committee of the Japan Association of Corrosion Control (JACC) has been conducting a marine corrosion test of thermal-sprayed Zn, Al, and Zn-Al coatings since 1986. The coating was applied to twelve steel pipes by arc- and flame-spraying to varied thicknesses and subjected to various post-spray treatments. The samples were set vertically into seawater at a port located approximately 80 km south of Tokyo. The corrosion performance of these coatings has been inspected annually by recording their appearance and thickness at the sea-air, splash, and tidal zones. No significant changes were observed for the first several years of exposure. After 7 years, however, Zn coatings with and without sealing started to suffer degradation in the immersed portion. Contrary to this, most of the Al and Zn-Al coatings still exhibit superb corrosion performance. In order to place the test in a proper perspective, a special team of about 20 members was formed to conduct a survey on corrosion prevent...

Relationship between Yield Strength and Near-Neutral pH Stress Corrosion Cracking Resistance of Pipeline Steels—An Effect of Microstructure

Abstract: In this paper the relationship between the near-neutral pH stress corrosion cracking (SCC) resistance and the yield strength of pipeline steels was investigated and an attempt was made to ...

Effect of Temperature on Inhibitive Action of Damsissa Extract on the Corrosion of Steel in Acidic Media

Abstract: The inhibitive effect of damsissa (Ambrosia maritime, L.) plant extracts on the corrosion of steel in an aqueous solution of 1 M sulfuric acid (H2SO4) was investigated in the temperature range from 25°C to 40°C using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The stability of the inhibition efficiency of damsissa extracts with immersion time was examined by weight-loss measurements at 30°C and 60°C. Potentiodynamic polarization curves indicated that the damsissa extract behaves as a mixed-type inhibitor. EIS measurements showed that the dissolution process occurs under activation control. The corrosion rates of steel and the inhibition efficiencies of the extract obtained from impedance and polarization measurements were in good agreement. Inhibition was found to increase with an increasing concentration of the plant extract but decreases with increasing temperature. The results obtained show that the damsissa extract could serve as an effective inhi...

Basics Revisited: Kinetics of Iron Carbonate Scale Precipitation in CO2 Corrosion

Abstract: Glass cell experiments were conducted to understand kinetics of iron carbonate scale formation in pure carbon dioxide (CO2) corrosion of mild steel. Weight gain and loss (WGL) method was used as a direct approach to investigate kinetics of scale formation. The experiments were done at the temperatures of 60C to 90C, and an iron carbonate supersaturation range of 12 to 350. It is found that the calculated results obtained by the previous kinetics expressions using the traditional dissolved ferrous ion concentration method are one to two orders of magnitude higher than the experimental precipitation rates obtained in the present study by the WGL method. The results show that the main source of the ferrous ions which are involved in formation of the protective iron carbonate scale is the iron dissolution process. It has been clearly demonstrated that the precipitation rate of iron carbonate is directly related to the conditions at the steel surface which can frequently be very different from the one in the bulk fluid.

Pitting corrosion of steam turbine blading steels: The influence of chromium content, temperature, and chloride ion concentration

Abstract: Two industry-standard steam turbine blading steels, FV566 containing 11% Cr and FV520B containing 13.5% Cr by weight, are characterized with respect to chloride-induced pitting corrosion u...

Effect of Temperature and Pressure on the Morphology of Carbon Dioxide Corrosion Scales

Abstract: Carbon dioxide (CO2) corrosion product scales of three kinds of oil well steel were obtained from simulated tests in autoclaves at varying temperatures and pressures. The effect of tempera...

Electrochemical Behavior of API X70 Steel in Hydrogen Sulfide-Containing Solutions

Abstract: As an attempt to contribute to the understanding of the cor- rosion process of steel by hydrogen sulfi de (H2S), the corro- sion behavior of an X70 pipeline steel immersed in several H2S-containing solutions is analyzed in this work. Linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques were used in order to charac- terize the corrosion behavior of X70 steel in H2S-containing solutions. Electrochemical parameters such as charge-transfer resistance, Rct, polarization resistance, Rp, and corrosion rate are presented in this work. Additionally, a comparison be- tween static and turbulent fl ow conditions was made in order to describe the corrosion behavior of X70 steel. Turbulent fl ow conditions were controlled using the rotating cylinder electrode (RCE) (at 1,000 rpm) in a saturated H2S solution.

Localized Corrosion Susceptibility of Alloy 22 in Chloride Solutions: Part 2 Effect of Fabrication Processes

Abstract: The effect of fabrication processes on the localized corrosion susceptibility of Alloy 22 ([UNS N06022] 56Ni-22Cr-13.5Mo-3W-4Fe), a candidate container material for the disposal of high-level nuclear waste in the proposed repository at Yucca Mountain, Nevada, was assessed in chloride-containing solutions at temperatures ranging from 60°C to 95°C. The results of tests covering a range of metallurgical conditions, including as-welded, welded plus solution-annealed, and thermally aged materials, were compared with those for the as-received mill-annealed alloy. The localized corrosion susceptibility of Alloy 22 was determined by comparing the crevice corrosion repassivation potentials with corrosion potentials measured in separate tests. The crevice corrosion susceptibility was found to be dependent on temperature, chloride concentration, and the nitrate-to-chloride molar concentration ratio. Welding and short-term thermal aging decreased the localized corrosion resistance of Alloy 22 compared with t...

Protective Iron Carbonate Films— Part 2: Chemical Removal by Dissolution in Single-Phase Aqueous Flow

Abstract: The dissolution of deposited, protective iron carbonate films in oil and gas transportation pipelines may drastically enhance corrosive processes on steel surfaces, and thus, seriously aff...

Solution Chemistry Effects on Corrosion of Carbon Steels in Presence of CO2 and Acetic Acid

Abstract: The corrosion behavior of X65 pipeline steel in solutions containing carbon dioxide (CO2), acetic acid (CH3COOH, abbreviated HAc) and 0.1-0.3 % sodium chloride (NaCl) was investigated on rotating cylinder specimens in glass cells. The tests were carried out at 25 C (1 bar CO2) and 80 C (0.5 bar CO2). The initial concentration of HAc was varied between 0 and 600 ppm (0-10 mM). The ferrous ion (Fe) concentration was in most of the tests held far below the iron carbonate (FeCO3) saturation limit. The electrode rotation rate was 1900 RPM, corresponding to ca. 1 m/s peripheral velocity. At 25 C the HAc inhibited general corrosion, but promoted formation of deep corrosion pits. At 80 C the corrosion was uniform; the corrosion rates were high (several tens of mm/y) in presence of HAc. The literature on CO2 corrosion in presence of HAc was reviewed. Some studies reported increased corrosivity in presence of HAc, whereas others reported that HAc works as an inhibitor. Most of the corrosion data reported in the literature was, however, found to be consistent when the effect of temperature and type of corrosion attack observed in the present work was taken into consideration. The literature data indicated that HAc corrosion could be mitigated by means of corrosion inhibitors and pH control. The physiochemical properties of HAc was also reviewed: diffusion coefficient, partial pressure of HAc over aqueous HAc solutions, HAc solubility in oil, and formation constants of ferrous and calcium acetate complexes. The effect of complex formation was investigated and discussed.

Use of Artificial Neural Networks for Predicting Crude Oil Effect on Carbon Dioxide Corrosion of Carbon Steels

Abstract: The role of crude oil on carbon dioxide (CO2) corrosion has gained special attention in the last few years because of its significance when predicting corrosion rates. However, the complex...