Showing papers in "Corrosion in 1998"

Role of Conductive Corrosion Products in the Protectiveness of Corrosion Layers

Abstract: In carbon dioxide (CO2) corrosion of steels, the bicarbonate ion (HCO3−) is simultaneously the buffer for carbonic acid (H2CO3), the source of iron carbonate (FeCO3) precipitation, and the product of the cathodic reaction. In addition to spatial separation of the production of Fe2+ and HCO3−, galvanic coupling between the steel and cementite (Fe3C) layers is the principal cause of internal acidification in these layers, since the HCO3− ions are removed from the steel surface by electromigration. This can facilitate localized corrosion by lateral galvanic coupling. This mechanism explains the role of traces of free acetic acid (CH3COOH, or HAc) and the existence of multiple steady states. Transposition to corrosion of iron by hydrogen sulfide (H2S) or to corrosion of copper is discussed.

Effect of the Amine Functional Group on Corrosion Rate of Iron Coated with Films of Organofunctional Silanes

Abstract: Silane pretreatments were investigated as environmentally friendly replacements for the existing chromating processes. The objective was to compare the corrosion protection properties of v...

In-Situ Monitoring of Pitting Corrosion in Aluminum Alloy 2024

Abstract: An in-situ monitoring method was used to observe the initiation sites and the processes of pitting corrosion in aluminum alloy 2024-T3 (UNS A92024) in real time. These observations complemented more detailed information about composition and distribution of constituent particles, pre- and post-corrosion surface morphology, and the internal morphology of corrosion pits. In-situ observations provided a comprehensive view of the development of localized corrosion in real time. Results confirmed the importance of intermetallic constituent particles in promoting initiation and growth of pits in aluminum alloys. Heterogeneous distribution of these particles served to define the location and extent (or severity) of pitting. A conceptual model was proposed as a framework for continued research. The formation of occluded cells under corrosion product domes over severe pits was observed. This formation will be incorporated into an overall reconsideration and modeling of the processes of pitting corrosion o...

Effect of Microstructure on Corrosion of Steels in Aqueous Solutions Containing Carbon Dioxide

Abstract: The influence of microstructure on the corrosion rate of steels in a carbon dioxide (CO2)-containing aqueous solution was measured experimentally as a function of pH, temperature, and part...

Inhibition of Mild Steel Corrosion by Sodium Dodecyl Benzene Sulfonate and Sodium Oleate in Acidic Solutions

Abstract: Inhibition of mild steel corrosion by sodium dodecyl benzene sulfonate ((C12H25C6H4SO3Na [SDBS]) and sodium oleate (CH3[CH2]7CH=CH[CH2]7COONa) in acidic solutions was investigated using a ...

Factors Controlling Naphthenic Acid Corrosion

Abstract: A laboratory study was conducted to elucidate the influence of chemical and physical parameters on corrosion of type 1018 carbon steel (CS, UNS G10180)and 5% Cr-0.5% Mo steel in oils conta...

Corrosion Inhibition of a Mild Steel by Aniline and Alkylamines in Acidic Solutions

Abstract: Corrosion inhibition of a mild steel in acid solutions by alkylamines (ALK-AM) and aniline hydrochloric (ANL-HCl) salts was investigated in the presence of sodium sulfate (Na2SO4) and sodium chloride (NaCl) using a potentiostat, a contact-angle goniometer, a scanning electron microscope (SEM), a Fourier transform infrared spectrometer (FTIR), and an atomic force microscope (AFM). Results showed chloride ions (Cl−) had a pronounced effect on inhibition of amines and ANL for corrosion of mild steel. In the presence of Cl− ions, cationic types of surfactants (ALK-AM and ANL) were attached to the surface through formation of chloride precipitate at the surface. In the absence of the organic inhibitors, corrosion initiated along grain boundaries of ferrite and pearlite structures. In the presence of the organic inhibitor, however, the steel surface was covered by an organic salt precipitation, and the corrosion rate was reduced significantly.

Low-Toxicity Copper Corrosion Inhibitors

Abstract: The efficiency of various imidazole derivatives as corrosion inhibitors for copper in hydrochloric and sulfuric acids (HCl and H2SO4) was investigated. Electrochemical measurements showed the organic compounds investigated have fairly good inhibiting properties, except for 4-methyl-5-imidazole-carbaldehyde in HCl. Protecting properties of most imidazole derivatives were close to those of commercial inhibitors for copper. Evaluation of the toxicity of the water solutions on the biological system for treatment of waste water — as measured in regard to chemical oxygen demands (COD), aerobic, and anaerobic toxicity — showed the tested inhibitors have relatively low toxicity.

Monitoring Localized Corrosion Processes and Estimating Localized Corrosion Rates Using a Wire-Beam Electrode

Abstract: A wire-beam electrode (WBE) fabricated from 100 mild steel wires was used to study the localized corrosion processes of mild steel exposed to several typical corrosive environments. Results confirmed the applicability of a WBE in simulating and monitoring various types of localized corrosion. A new method of localized corrosion rate estimation was developed using a WBE.

Analytical characterization of the passive film formed on steel in solutions simulating the concrete interstitial electrolyte

Abstract: Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) were used to study the effect of chloride (Cl−) and fly ash on behavior of the passive film formed on steel in ...

Application of the Pitting Resistance Equivalent Concept to Some Highly Alloyed Austenitic Stainless Steels

Abstract: The influence of alloying levels in the ranges from 0.01% to 0.5% N, 4.5% to 6% Mo, and 0.2% to 10% Mn on pitting corrosion resistance was investigated for austenitic stainless steels (SS)...

Hydrogen-Facilitated Anodic Dissolution of Austenitic Stainless Steels

Abstract: Effects of hydrogen in alloys on their anodic polarization curves and the dissolution behavior of types 304 and 310 (UNS 30400 and UNS 31000) stainless steels (SS) in 0.5 M sulfuric acid (...

Corrosion of alloy 625 in aqueous solutions containing chloride and oxygen

Abstract: Alloy 625 (UNS N06625) is used frequently as a reactor material for the oxidation of hazardous organic wastes in supercritical water (supercritical water oxidation [SCWO]). In the presence of chloride (Cl−) and oxygen (O2), all Ni-based alloys corrode fast in high-temperature, subcritical water. High-pressure, high-temperature-resistant tube reactors made of alloy 625 were used as specimens. Coupons were exposed simultaneously inside the test tubes. Experimental conditions included temperatures up to 500°C and pressures up to 38 MPa. Pitting corrosion was observed at temperatures above ≈ 130°C to 215°C. At higher temperatures (up to the critical temperature of water), transpassive dissolution dominated. Under certain conditions, transgranular stress corrosion cracking (TGSCC) appeared in the transition zone between the passive and transpassive regions leading to premature failure of the test reactors. Parts of the corrosion products were insoluble in supercritical water and formed thick layers in...

Electrochemical Impedance Spectroscopy and Surface Characterization Techniques to Study Carbon Dioxide Corrosion Product Scales

Abstract: Electrochemical impedance spectroscopy (EIS) was used to study carbon dioxide (CO2) corrosion product scales and their effects on further CO2 corrosion. Objectives were to determine the suitability of EIS for studying corrosion scales and to investigate the influence of environmental factors on scale formation. EIS provided useful information about protective abilities and electrochemical properties of corrosion scales. CO2 corrosion scales formed at high-temperature and pressure provided better protection than those formed at low-temperature and pressure. The level of protection of the scale formed at higher temperature and pressure increased with exposure time. EIS results were compared with coupon weight-loss measurements. Scales were analyzed using a combination of Fourier transform infrared (FTIR) analysis, x-ray diffraction (XRD), and electron microscopy.

Using Indole to Inhibit Copper Corrosion in Aerated 0.5 M Sulfuric Acid

Abstract: Inhibition of copper corrosion in aerated 0.5 M sulfuric acid (H2SO4) solutions containing various concentrations of indole was studied in the temperature range from 25°C to 55°C using pot...

Investigation of the Electrochemical Corrosion Behavior and Passive Film for Fe-Mn, Fe-Mn-Al, and Fe-Mn-Al-Cr Alloys in Aqueous Solutions

Abstract: The corrosion behavior of austenitic Fe-(17 wt% to 31 wt%) Mn-(1 wt% to 9 wt%) Al-(1 wt% to 7 wt%) Cr alloys in different aqueous solutions and the corrosion protection mechanism induced b...

Corrosion of Iron in Acid Solutions with Hydrogen Sulfide

Abstract: The influence of pH and the concentration of hydrogen sulfide (H2S) on corrosion of iron in acid solutions was studied using a potentiostatic polarization method. The alternating current (AC) impedance technique also was used to characterize the active dissolution process of iron. Results showed the dissolution process was accelerated by H2S. The anodic dissolution current (ia) increased with pH and H2S concentration with reaction orders of about npH = nH2S = 0.25 when the ratio of H2S concentration and hydrogen ion (H3O+) concentration was 101.5. The Nyquist diagram corresponding to the active dissolution process in the Tafel range exhibited two capacitive loops in addition to the well-known, high-frequency capacitive loop. A mechanism was proposed to explain the results in which H2S chemisorbed first on the electrode surface and then catalyzed the anodic dissolution of iron in two discharging steps.

Effect of Natural Marine Biofilms on Galvanic Corrosion

Abstract: Galvanic corrosion of copper (UNS C11000), 1018 carbon steel (CS, UNS G10180), aluminum alloy 3003 (UNS A93003), and zinc (UNS Z32121) coupled to cathodes of UNS N08367 was tested with and...

Microstructure Analysis of Coupons Exposed to Carbon Dioxide Corrosion in Multiphase Flow

Abstract: Carbon dioxide (CO2) corrosion products formed on low-carbon steel test coupons exposed to multiphase flows of CO2-oil-salt water mixtures were analyzed. The effects of flow, temperature, ...

Thermal transition effects and electrochemical properties in organic coatings. Part 1: Initial studies on corrosion protective organic coatings

Abstract: Thermal effects in a high-performance fusion-bonded epoxy (FBE) powder coating on steel were measured by electrochemical means. Experimental performance of the coating in immersion indicated the coating resistance as acquired by electrochemical noise methods (ENM), electrochemical impedance spectroscopy (EIS), and direct current resistance (RDC) measurements decreased in an Arrhenius manner with increasing temperature up to the glass transition temperature (Tg) of the immersed coating film. Coating resistance then abruptly decreased more rapidly. The abrupt change in film resistance (a coating transport property) at Tg was seen in all three film resistance measures. Using independent differential scanning calorimetry (DSC) experiments, Tg was shown to be that of the water-plasticized film and not of the dry film. Calculation of film capacitance values from EIS indicated increased water uptake with temperature consistent with water-plasticization as seen in Tg measurements. Data implied that use o...

Effect of Natural Marine Biofilms on Galvanic Corrosion Predicted Using Potentiodynamic Polarization Curves

Abstract: Abstract Galvanic corrosion of copper (UNS C11000), 1018 carbon steel (CS, UNS G10180), aluminum alloy 3003 (UNS A93003), and zinc (UNS Z32121) coupled to cathodes of UNS N08367 was tested with and...

Roles of H2S in the Behavior of Engineering Alloys: A Review of Literature and Experience

Abstract: Hydrogen sulfide (H{sub 2}S) has long been associated with the cause of corrosion damage and sulfide stress cracking (SSC) in high strength steels and high hardness weldments used in oil and gas production, petroleum refining, and petrochemical/chemical processing. Other applications where sulfide species have produced environmental cracking include heavy water production, electric power, marine applications and many others where sulfate reducing bacteria can flourish and oftentimes produce substantial amounts of H{sub 2}S. H{sub 2}S has also been associated with internal blistering, hydrogen induced cracking (HIC) and stress oriented hydrogen induced cracking (SOHIC) of carbon steels used in refinery vessels in wet H{sub 2}S service and pipelines containing sour (H{sub 2}S-containing) fluids. In recent years, new stainless alloys have been implemented in lieu of conventional steels in many applications where H{sub 2}S corrosion is particularly severe. These materials have been used along with chemical inhibitors to mitigate corrosion. These alloys, however, may in some cases also be susceptible to SSC, localized corrosion and anodic stress corrosion cracking (SCC) in sour environments. In this review, the behavior of carbon and low-alloy steels, stainless steels, and nickel alloys in sour environments is discussed. Emphasis is placed on the identification of the various typesmore » of H{sub 2}S-related corrosion and environmental cracking that can occur, the origin and mechanisms, and the methods of control.« less

Green Chemistry Applied to Corrosion and Scale Inhibitors

Abstract: Numerous breakthroughs in environmental protection and pollution prevention have been realized in recent years by both industry and academia through the application of green chemistry principles. Green chemistry, or pollution prevention at the molecular level, is chemistry designed to reduce or eliminate the use or generation of hazardous materials associated with the manufacture and application of chemicals. The application of the green chemistry principles to the areas of corrosion and scale inhibitors has resulted in the reduction/elimination of many of the more toxic inhibitors and the development of newer, more environmentally friendly ones.

Effect of precorrosion on the performance of inhibitors for CO2 corrosion of carbon steel

Abstract: Four commercially available, water soluble corrosion inhibitors for CO corrosion have been tested in the laboratory on carbon steel specimens that were corroded for up to 18 days in the medium prior to inhibitor addition. The tests were performed at 20-50 °C, pH 5, 1 bar CO, 1-3 w% NaCl in glass cells and a glass loop. The results show that inhibitor performances were impaired with increasing precorrosion time and increasing temperature. The resulting corrosion attack was localised within deep pits. The detrimental effect is influenced both by the nature of the steel and the inhibitor composition. The inhibitor failure is related to the formation of a cementite layer at the steel surface.

Influence of Alloy Sulfur Content and Bulk Electrolyte Composition on Crevice Corrosion Initiation of Austenitic Stainless Steel

Abstract: The influence of alloy sulfur content and bulk solution composition on crevice corrosion initiation of type 304 (UNS S30400) stainless steel (SS) in neutral chloride solutions was determin...

Hydrogen Evolution and Enrichment Around Stress Corrosion Crack Tips of Pipeline Steels in Dilute Bicarbonate Solution

Abstract: Hydrogen involvement in the process of stress corrosion cracking (SCC) of pipelines in a dilute bicarbonate solution was studied. Hydrogen distributions in the steels were determined using...

Dissolution and corrosion inhibition of copper, zinc, and their alloys

Abstract: The corrosion behavior of copper, zinc, and their alloys in sulfuric acid (H2SO4) solutions with oxygen and ferric ions (Fe3+) was studied using a potentiostat. Oxygen and Fe3+ ions were s...

Voltammetric Microelectrodes for Biocorrosion Studies

Abstract: Understanding various biocorrosion mechanisms requires direct measurement of chemical concentrations and profiles within thin biofilms or discrete biodeposits. A gold-based mercury microelectrode was developed for simultaneous measurement of dissolved O2, Mn, Fe, S(-II), and low pH using square wave voltammetry. It was constructed by electroreducing Hg(II) on a gold wire of 25-μm diameter encased in glass. By mounting the electrode on a computerized micromanipulator, vertical microprofiles of the key redox species were measured with 10-μm depth resolution across marine biofilms formed on metal coupons. Various interfering factors and experimental parameters of the voltammetric measurements were reviewed. Results revealed the heterogeneous nature of the biofilm and complex microbially mediated heavy metal (Mn and Fe) cycles within the film system. Data interpretation provided further insight into the mechanism of microbiologically influenced metal corrosion.