Showing papers in "Corrosion in 1997"
TL;DR: In this article, molecular orbital theoretical calculations based on the modified neglect of differential overlap (MNDO) method were performed on some substituted methyl pyridines and substituted ethane derivatives in common use as corrosion inhibitors for iron in acid media.
Abstract: Molecular orbital theoretical calculations based on the modified neglect of differential overlap (MNDO) method were performed on some substituted methyl pyridines and substituted ethane derivatives in common use as corrosion inhibitors for iron in acid media. New correlations of corrosion rates with the energy of the highest occupied molecular orbital (EHOMO), the energy gap or difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital (ELUMO − EHOMO), and Hammett's parameter (σ) were presented. Absolute electronegativity (χ) values and the fraction of electrons (ΔN) transferred from substituted pyridine and ethane compounds to iron in the bulk metal were calculated and correlated with corrosion rates for the first time.
466 citations
TL;DR: In this article, the corrosion behavior of copper in aqueous solutions of different pH values was investigated using electrochemical and surface analysis methods, and it was shown that the corrosion mechanism changed with pH and was associated with morphology of the surf ace films formed.
Abstract: The corrosion behavior of copper in aqueous solutions of different pH values was investigated using electrochemical and surface analysis methods. It was shown that the corrosion mechanism changed with pH and was associated with morphology of the surf ace films formed. In solution of pH 3, the copper surface was covered with porous corrosion products of cuprous oxide (Cu2O). Corrosion was controlled predominately by diffusion in solution. In solutions of pH 4 to pH 5, formation of cubic Cu2O on the copper surface provided a diffusion barrier to copper dissolution. The anodic process was controlled by a mixed diffusion of copper ions in oxide films and in solution. In solutions of pH 6 to pH 9, the oxide films (Cu2O) became more protective. Diffusion in the oxide films became a rate-determining step of anodic dissolution. In pH 10 solution, a thin, compact Cu2O film formed, and spontaneous passivation was observed. At pH 12 and pH 13, analysis by x-ray photoelectron spectroscopy (XPS) and scanning ...
202 citations
TL;DR: Corrosion and passivation of solution-treated and aged (STA), and diffusion-hardened (DH) variants of Ti-13% Nb- 13% Zr (Ti-13-13) were examined in a simulated physio...
Abstract: Corrosion and passivation of solution-treated (ST), solution-treated and aged (STA), and diffusion-hardened (DH) variants of Ti-13% Nb-13% Zr (Ti-13-13) were examined in a simulated physio...
196 citations
TL;DR: In this paper, the interaction of corrosion inhibitors with metal surfaces in acidic solutions was investigated using a nonlinear model encompassing the Langmuir adsorption isotherm and a regression equation.
Abstract: Interaction of corrosion inhibitors with metal surfaces in acidic solutions was investigated using a nonlinear model encompassing the Langmuir adsorption isotherm. A regression equation, w...
101 citations
TL;DR: In this article, the electrochemical behavior of 55% Al-Zn coated steel sheet was studied using electrochemical impedance spectroscopy (EIS) using a very thin polymeric film (≈ 1 μm).
Abstract: The electrochemical behavior of 55% Al-Zn coated steel sheet, on which a very thin polymeric film (≈ 1 μm) was applied, was studied using electrochemical impedance spectroscopy (EIS). Use ...
100 citations
Journal Article•
TL;DR: In this paper, Electrochemical Noise (ECN) and Electrochemical Impedance Spectroscope (EIS) measurements were made simultaneously in a 75 mm I.D., 10 m long acrylic pipeline using salt-water/carbon dioxide mixtures.
Abstract: Electrochemical Noise (ECN) and Electrochemical Impedance Spectroscope (EIS) measurements were made simultaneously in a 75 mm I.D., 10 m long acrylic pipeline using salt-water/carbon dioxide mixtures. Full pipe flow was studied for liquid velocities of 0.5, 0.75, 1.1, 1.5 m/s and slug flow for Froude numbers 4, 6 and 9. Experiments were carried out at a constant pressure of 136 kPa and temperature of 40 C. ECN data were measured with a fast auto zero resistance ammeter. The ECN technique is able to detect changes in flow regime, showing distinct differences between full pipe flow and slug flow. The choice of sampling rate when using ECN is very important. For slug flows, sampling rates as high as 100 Hz are necessary to include most of the transients in the flow. Distinct differences can be seen in the Fast Fourier Transforms where dominant frequencies exist which correspond to possible bubble action in the slug body. EIS can be used to measure corrosion rate in multiphase flows. It does show an increase in the corrosion rate with liquid flow rates for full pipe flow and Froude numbers for stationary slug flow. A simple statistical analysis of ECN response gives a correlation withmore » corrosion rate. These show ECN could be a very powerful tool for determining corrosion rate and corrosion mechanism in multiphase flow.« less
91 citations
Journal Article•
TL;DR: In this paper, the combined effect of HNO 3, NaCl, and temperature on the general corrosion behavior of 304 stainless steel (SS) was examined, and the corrosion response of 304 SS was bifurcated: materials were either continuously passive following immersion or spontaneously passivated following a period of active dissolution.
Abstract: In an effort to examine the combined effect of HNO 3 , NaCl, and temperature on the general corrosion behavior of 304 stainless steel (SS), electrochemical studies were performed. The corrosion response of 304 SS was bifurcated: materials were either continuously passive following immersion or spontaneously passivated following a period of active dissolution. Active dissolution was autocatalytic, with the corrosion rate increasing exponentially with time and potential. The period of active corrosion terminated following spontaneous passivation, resulting in a corrosion rate decrease of up to five orders of magnitude. The length of the active corrosion period was strongly dependent on the solution volume-to-surface area ratio. This finding, coupled with other results, suggested that spontaneous passivation arises solely from solution chemistry as opposed to changes in surface oxide composition. Increasing NaCl concentrations promoted pitting, active dissolution upon initial immersion, a smaller potential range for passivity, longer active corrosion periods, larger active anodic charge densities preceding spontaneous passivation, and larger corrosion current and peak current densities. In contrast, intermediate HNO 3 concentrations promoted active dissolution, with continuous passivity noted at HNO 3 concentration extremes. During active corrosion, increased HNO 3 concentrations increased the anodic charge density, corrosion current density, and peak current density. The time required for spontaneous passivation was greatest at intermediate HNO 3 concentrations. Susceptibility to pitting was also greatest at intermediate HNO 3 concentrations: the pit initiation and repassivation potentials decreased with increasing HNO 3 concentration until the HNO 3 concentration exceeded a critical concentration beyond which susceptibility to pitting was entirely eliminated. Increasing solution temperature increased the susceptibility to both pitting and active dissolution.
80 citations
TL;DR: In this article, a corrosion rate equation was derived on the basis of fundamental reaction rate theory and compared to empirically determined relationships reported in the literature, and the application limit for this equation extends to the point where corrosion becomes diffusion-controlled as a result of the formation of stable corrosion products on the steel surface.
Abstract: Corrosion of steel in carbon dioxide (CO2)-containing solutions is considered a chemical reaction-controlled process. A corrosion rate equation was derived on the basis of fundamental reaction rate theory and compared to empirically determined relationships reported in the literature. The predictive equation was developed as a function of pH, partial pressure of CO2 (PCO2), and temperature. The equation allows the inclusion of other variables, such as flow, impurities, inhibitors, and steel microstructure, through the reaction constant. The application limit for this equation extends to the point where corrosion becomes diffusion-controlled as a result of the formation of stable corrosion products on the steel surface.
77 citations
TL;DR: In this article, a systematic investigation of the ability of the homologous straight chain mono-and α,ω-dicarboxylates to inhibit corrosion of mild steel, copper, and aluminum in aerated, mildly saline, and near neutral aqueous solutions was conducted.
Abstract: Electrochemical methods were used in a systematic investigation of the abilities of the homologous straight chain mono- and α,ω-dicarboxylates to inhibit corrosion of mild steel, copper, and aluminum in aerated, mildly saline, and near-neutral aqueous solutions. Performance of both compound types was shown to be critically dependent upon their chain length, the metal, and the number of carboxylate groups. For dicarboxylates, with the possible exception of mild steel, longer chain lengths were found advantageous. This was not true for monocarboxylates, which showed abrupt decreases in inhibitor ability outside the optimal range. The dramatic variations in inhibitor efficiencies probably resulted from competing reactions, such as adsorption and complexation at the metal (hydr/oxide) surface, solubility, and micelle formation.
77 citations
TL;DR: In this article, Grey relational analysis makes use of relatively simple mathematical procedures to arrive at salient relationships in a complex system and uses a relatively small amount of data and works well on complex systems.
Abstract: Grey relational analysis makes use of relatively simple mathematical procedures to arrive at salient relationships in a complex system. It uses a relatively small amount of data and works ...
74 citations
Journal Article•
TL;DR: A fiber-optic pH-imaging sensor array capable of both visualizing remote corrosion sites and measuring local chemical concentrations at these sites was applied to real-time corrosion monitoring as mentioned in this paper.
Abstract: A fiber-optic pH-imaging sensor array capable of both visualizing remote corrosion sites and measuring local chemical concentrations at these sites was applied to real-time corrosion monitoring. The imaging fiber's distal face, containing an immobilized pH-sensitive fluorescent dye, was brought into contact with metal surfaces submerged in aqueous buffers and fluorescence images were acquired as a function of time. Heterogeneous fluorescence signals were observed due to both pH increases at cathodic surface sites and pH decreases at anodic surface sites. These fluorescence signals showed both localization and rates of corrosion activity. Three corrosion processes were investigated, galvanic corrosion at a copper/aluminum interface and crevice corrosion and pitting at a stainless steel surface. The spatial resolution of the technique was limited by proton/hydroxide diffusion and the diameter of the individually clad optical fibers comprising the imaging bundle.
TL;DR: In this paper, a mathematical model was proposed for determining the crack growth rate of hydrogen-induced cracking (HIC) in steel plates exposed to a sour gas, and the model showed reasonable agreement with experimental results, which correspond to the first stages of HIC growth.
Abstract: A mathematical model was proposed for determining the crack growth rate of hydrogen-induced cracking (HIC) in steel plates exposed to a sour gas. The model assumes that the extension of an embedded circular crack results from accumulation of internal hydrogen pressure that produces a rise of the stress intensity factor in excess of the plane strain fracture toughness of the steel with dissolved hydrogen. Upon crack extension, the volume of the crack cavity increases, and the pressure drops, causing the crack to arrest. As the cavity is filled again with hydrogen, the process is repeated. HIC experiments were conducted on API 5L-X52 steel plates, using ultrasonic inspection to measure crack sizes. Data from inspected sour gas pipelines were gathered and compared to the predicted crack growth rates. The model showed reasonable agreement with experimental results, which corresponded to the first stages of HIC growth. It failed to approximate values for large crack lengths found in pipelines after long exposure to sour gas. This suggested either that there were important crack delay processes or that the cracking criterion changed as the crack grew. These delay processes were related to the effect of metallurgical variables.
TL;DR: In this paper, current and potential fluctuations between two nominally identical carbon steel electrodes were recorded in a solution of sodium phosphate (Na3PO4) at difference times.
Abstract: Current and potential fluctuations (electrochemical noise [EN]) between two nominally identical carbon steel electrodes were recorded in a solution of sodium phosphate (Na3PO4) at differen...
TL;DR: In this article, observed and simulated electrochemical noise (EN) from general and localized corrosion on uncoated metals was used to test theoretical concepts regarding the relation of electrode area and EN.
Abstract: Observed and simulated electrochemical noise (EN) from general and localized corrosion on uncoated metals was used to test theoretical concepts regarding the relation of electrode area and...
TL;DR: In this article, a fine-grained magnesium matrix with β-Mg17Al12 precipitates was used to synthesize fast solidified alloys with 8 at, 15 at, and 20 at% Al and 1 at% and 3 at% Zn.
Abstract: Rapidly solidified magnesium alloys with 8 at%, 15 at%, and 20 at% Al and 1 at% and 3 at% Zn were fabricated by centrifugal atomization followed by hot extrusion. Microstructure of the alloys was composed of a fine-grain magnesium matrix (0.5 μm) with β-Mg17Al12 precipitates. Electrochemical and weight-loss tests were performed in borate and ASTM D 1384 solution (chloride, carbonate, and sulfate). In both media, corrosion current of the alloys decreased with increases in aluminum or zinc content. In borate solution, a passivating plateau was observed from the corrosion potential (Ecorr) to Ecorr + 1,200 mV. Current density decreased with aluminum and zinc concentrations. Electrochemical behavior of the synthesized matrix and precipitates was characterized. Zinc increased Ecorr of the two phases, with a corresponding decrease of corrosion current. The same trend was noticed for aluminum but with a less dramatic effect. The corrosion mechanism was suggested result from galvanic coupling of the matr...
TL;DR: In this paper, the effects of TTAH and BTAH corrosion inhibitors on anodic polarization behavior of copper in 1 M sodium chloride (SCL) was compared with tolytriazole and benzotriazole (BTAH) corrosion inhibitors.
Abstract: Potentiodynamic techniques were used to compare the effects of tolytriazole (TTAH) and benzotriazole (BTAH) corrosion inhibitors on anodic polarization behavior of copper in 1 M sodium chl...
TL;DR: In this paper, a mathematical model was developed to predict cathodic protection requirements for coated pipelines protected by parallel anodes, which is motivated by the need to estimate current and potential distribution on a pipe when anodes are placed nearby or when discrete coating holidays expose bare steel.
Abstract: Mathematical models were developed to predict cathodic protection (CP) requirements for coated pipelines protected by parallel anodes. This work was motivated by the need to estimate current and potential distribution on a pipe when anodes are placed nearby or when discrete coating holidays expose bare steel. The mathematical model solves Laplace's equation for potential with boundary conditions appropriate for the pipe being protected, the anode, and any region through which current does not pass. The current density on bare steel was assumed to be composed of contributions from corrosion, reduction of dissolved oxygen, and evolution of hydrogen. Kinetic parameters were obtained from independent experiments. The anode was assumed to have a constant potential, and current was allowed to flow through the coating under the assumption that the coating is a high-resistance ionic conductor. A boundary element technique coupled with Newton-Raphson iteration was used to solve the governing equations for...
TL;DR: In this paper, the behavior of steel in chloride-free and chloride-contaminated simulated concrete solutions was studied to observe the degradation of steel as a result of addition of chlorides.
Abstract: The behavior of steel in chloride-free and chloride-contaminated simulated concrete solutions was studied to observe the degradation of steel as a result of addition of chlorides. One of t...
TL;DR: Corrosion protection of aluminum metal-matrix composites (MMC) by anodizing treatments was investigated in this paper, and the behavior of MMC without protection also was investigated.
Abstract: Corrosion protection of aluminum metal-matrix composites (MMC) by anodizing treatments was investigated Electrochemical behavior of MMC without protection also was investigated Electroch
TL;DR: In this article, a boundary element mathematical model was used to assess the influence of cathodic protection (CP) design parameters on performance of a parallel-ribbon sacrificial anode CP system for coated pipelines.
Abstract: A boundary element mathematical model was used to assess the influence of cathodic protection (CP) design parameters on performance of a parallel-ribbon sacrificial anode CP system for coated pipelines. The model accounted for current and potential distributions associated with discrete holidays on coated pipelines that expose bare steel to the environment. Case studies, based on the CP system used to provide protection to the Trans-Alaska pipeline, were selected to show conditions under which a given CP system will and will not protect a pipe. In the cases studied, Mg ribbons provided adequate protection in 50 kΩ-cm soil, but almost no additional protection was achieved by retrofitting Mg anodes to a CP system using Zn ribbons if the Zn ribbons remained connected to the pipe. The model also was used to show the lack of sensitivity of aboveground on-potential surveys to localized corrosion on the buried pipe.
Journal Article•
TL;DR: In this article, a boundary element mathematical model was used to assess the influence of cathodic protection (CP) design parameters on performance of a parallel-ribbon sacrificial anode CP system for coated pipelines.
Abstract: Abstract A boundary element mathematical model was used to assess the influence of cathodic protection (CP) design parameters on performance of a parallel-ribbon sacrificial anode CP system for coated pipelines. The model accounted for current and potential distributions associated with discrete holidays on coated pipelines that expose bare steel to the environment. Case studies, based on the CP system used to provide protection to the Trans-Alaska pipeline, were selected to show conditions under which a given CP system will and will not protect a pipe. In the cases studied, Mg ribbons provided adequate protection in 50 kΩ-cm soil, but almost no additional protection was achieved by retrofitting Mg anodes to a CP system using Zn ribbons if the Zn ribbons remained connected to the pipe. The model also was used to show the lack of sensitivity of aboveground on-potential surveys to localized corrosion on the buried pipe.
TL;DR: In this article, the authors evaluated the performance of three different anilines (SABT, SACLBT, and SAMEOBT) as corrosion inhibitors for mild steel in 1 M hydrochloric acid (HCl) at concentrations from 100 ppm to 500 ppm and temperatures from 35°C to 60°C.
Abstract: The heterocyclic anils 2-salicylideneaminobenzothiazole (SABT), 2-salicylideneamino-6-chlorobenzothiazole (SACLBT), and 2-salicylideneamino-6-methoxybenzothiazole (SAMEOBT) were investigated to evaluate their efficiency as corrosion inhibitors for mild steel (MS) in 1 M hydrochloric acid (HCl) at concentrations from 100 ppm to 500 ppm and temperatures from 35°C to 60°C. SACLBT performed best, giving an inhibition efficiency as high as 98% even at a very low concentration and higher temperature. Potentiodynamic polarization studies showed inhibition was under cathodic control. These compounds reduced hydrogen permeation through MS in 1 M HCl solution. Adsorption on the MS surface followed Temkin's adsorption isotherms. Surface analysis of the MS surface exposed with SACLBT proved adsorption of this compound on the surface occurred through interaction of lone pairs of nitrogen, sulfur, and chlorine atoms with the metal surface.
TL;DR: The anodic polarization behavior of copper in a 0.1 M sulfuric acid + 1 M sodium sulfate (Na2SO4) solution (pH = 2.0) was studied at room temperature under quiescent and stirred co...
Abstract: The anodic polarization behavior of copper in a 0.1 M sulfuric acid (H2SO4) + 1 M sodium sulfate (Na2SO4) solution (pH = 2.0) was studied at room temperature under quiescent and stirred co...
TL;DR: In this article, a method was developed for construction of stability diagrams for metals in the presence of realistically modeled aqueous solutions, based on a comprehensive thermodynamic model of the system.
Abstract: A method was developed for construction of stability diagrams for metals in the presence of realistically modeled aqueous solutions. The method was based on a comprehensive thermodynamic m...
TL;DR: A study of hydrogen accumulation on grain boundaries, at inclusions, and near a kneaded notch tip was conducted in this paper, showing the susceptibility for blistering and hydrogen-induced cracking.
Abstract: A study was undertaken of hydrogen accumulation on grain boundaries, at inclusions, and near a kneaded notch tip; the susceptibility for blistering; and hydrogen-induced cracking (HIC) of ...
TL;DR: In this article, the authors reviewed available data on embrittlement of duplex stainless steels under cathodic protection (CP) in seawater, including some data previously unpublished, and found hydrogen embrittlements.
Abstract: Available data on embrittlement of duplex stainless steels (DSS) under cathodic protection (CP) in seawater, including some data previously unpublished, was reviewed. Results show hydrogen...
TL;DR: In this article, a laboratory study was conducted on the cavitation corrosion behavior of a commercial cast duplex stainless steel (DSS) in seawater using an ultrasonically induced cavitation facility.
Abstract: A laboratory study was conducted on the cavitation corrosion behavior of a commercial cast duplex stainless steel (DSS) in seawater using an ultrasonically -induced cavitation facility. Ma...
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TL;DR: In this article, a potentiostatic test for assessment of critical pitting (CPT) and crevice (CCT) temperatures was analyzed with respect to its ability to generate data relevant to chlorinated seawater systems.
Abstract: Relatively recent failures in seawater systems of highly alloyed (i.e., pitting resistance equivalent [PREN] > 40) stainless steels (SS) have highlighted the issue of corrosion testing and safe-use limits. Three aspects of testing and selection of SS for seawater application were reviewed: relevancy of the electrochemical test methods, the quality control system, and the importance of repassivation. A potentiostatic test for assessment of critical pitting (CPT) and crevice (CCT) temperatures was analyzed with respect to its ability to generate data relevant to chlorinated seawater systems. CPT seemed valid as safe-use limits, but the CCT determined were too high. A modified test approach was proposed. Generally, significant scatter in CCT and CPT values was registered, focusing on the importance of statistical experimental approach and data analyses. Recommendations were made on use of the ASTM G 48 test as a quality control method. The validity of critical pitting and crevice indices was analyze...
Journal Article•
TL;DR: In this paper, a mechanistic model was developed to predict corrosion rates in multiphase (water/oil/CO{sub 2}) flow conditions, taking into account electrochemistry, reaction kinetics, and, mass transport effects.
Abstract: A mechanistic model has been developed to predict corrosion rates in multiphase (water/oil/CO{sub 2}) flow conditions. The model takes into account electrochemistry, reaction kinetics, and, mass transport effects. This paper describes the equations used to determine pH and bulk concentrations of various ions, which are then used to calculate the mass transfer rates to the corrosion surface. The result includes the determination of the mass transfer coefficients of various ionic species and corrosion rates. Details of relations used for determination of mass transfer coefficients for multiphase flows, and rates of electrochemical reaction kinetics are discussed and predicted results are compared with experimental observations. Agreement between model results and experimental data is good.