Showing papers in "Corrosion in 2000"

Polarization Resistance Method for Determination of Instantaneous Corrosion Rates

Abstract: The polarization resistance method for the determination of instantaneous corrosion rates of metals were reviewed. The assumptions in electrode kinetics that govern the connection between the slope of steady-state applied electrochemical potential-applied current density (Eapp-iapp) measurements (i.e., the polarization resistance) and the corrosion rate were restated. Electrochemical impedance, as well as statistical and spectral electrochemical noise methods for obtaining polarization resistance, also were discussed. Traditional sources of error such as high excitation voltage amplitudes, insufficiently slow voltage ramp rates, high alternating current (AC) frequencies, inadequate polarization hold periods, high solution resistance, presence of parallel reduction-oxidation reactions, and nonuniform current and potential distributions were examined with the goal of defining some of the conditions and circumstances where these complicating factors are important. Other complicating factors such as ...

Electrochemical Behavior of Rust Formed on Carbon Steel in a Wet/Dry Environment Containing Chloride Ions

Abstract: The iron rust phase was analyzed by using the in-situ x-ray diffraction (XRD) and alternating current (AC) impedance methods after a wet/dry corrosion test using sodium chloride (NaCl) solution, which is the main composition of airborne saline particles. The corrosion content of the carbon steel depended on the concentration of Cl ions in the environment of the test chamber. As the concentration of Cl ions increased, the content of β-FeOOH increased in iron rust phases. The transition of β-FeOOH from the green rust I (GRI) was observed directly by in-situ XRD. The amount of GRI depended on the concentration of Cl ions, and β-FeOOH was transformed from GRI automatically in the dry process of the test. AC impedance showed that the resistance of the rust (Rrust) increased with the number of cycles in the corrosion test, and that the structural factor of the rust became predominant in Rrust. With the increase of the amount of rust, the resistance corresponding to the corrosion rate (Rt decreased, whi...

High-Resolution Characterization of Intergranular Attack and Stress Corrosion Cracking of Alloy 600 in High-Temperature Primary Water

Abstract: Intergranular (IG) attack regions and stress corrosion cracks in Alloy 600 (UNS N06600) U-bend samples tested in 330°C pressurized water reactor water were characterized by analytical tran...

Inhibition of pitting corrosion on aluminum alloy 2024-T3: Effect of soluble chromate additions vs. chromate conversion coating

Abstract: Pitting potentials (Epit) of aluminum alloy (AA) 2024-T3 (UNS A92024) were improved with additions of 0.01 M sodium chromate (Na2CrO4, pH 8) and 0.0062 M Na2CrO4 + 0.0038 M chromic acid (H2CrO4, pH 6) additions to 0.1 M sodium sulfate (Na2SO4) + 0.005 M sodium chloride (NaCl, pH 6) after 2-h periods at open-circuit potential (OCP). Chromate conversion coatings (CCC) on AA 2024-T3 also improved Epit in 0.1 M Na2SO4 + 0.005 M NaCl. However, CCC did not improve the Epit determined in fast potentiodynamic scans without periods at OCP. These tests were designed to minimize chromate leaching and long-range transport of chromate. The OCP of CCC AA 2024-T3, Al2Cu, Al2CuMg, 99.999% Cu, and 99.998% Al were not changed significantly in 0.1 M Na2SO4 + 0.005 M NaCl. Moreover, the OCP of AA 2024-T3, Al2Cu, Al2CuMg, and 99.999% Cu were not changed significantly in 0.1 M Na2SO4 + 0.005 M NaCl with the addition of 0.01 M soluble chromate at pH 6 and pH 8. The mass transport limiting current density for O2 reducti...

2,5-Bis(n-Pyridyl)-1,3,4-Oxadiazoles as Corrosion Inhibitors for Mild Steel in Acidic Media

Abstract: The effect of new corrosion inhibitors—namely, 2,5-bis(n-pyridyl)-1,3,4-oxadiazoles (n-POX)—on the corrosion of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulfuric acid (H2SO4) wa...

Relationship Between Corrosion and the Biological Sulfur Cycle: A Review

Abstract: Sulfur and sulfur compounds can produce pitting, crevice corrosion, dealloying, stress corrosion cracking, and stress-oriented hydrogen-induced cracking of susceptible metals and alloys. Even though the metabolic by-products of the biological sulfur cycle are extremely corrosive, there are no correlations between numbers and types of sulfur-related organisms and the probability or rate of corrosion. Determination of specific mechanisms for corrosion caused by microbiologically mediated oxidation and reduction of sulfur and sulfur compounds is complicated by the variety of potential metabolic/energy sources and by-products; the coexistence of reduced and oxidized sulfur species; competing reactions with inorganic and organic compounds; and the versatility and adaptability of microorganisms in biofilms. The microbial ecology of sulfur-rich environments is poorly understood because of the association of aerobes and anaerobes and the mutualism or succession of heterotrophs to autotrophs. The physical...

Conducting Polymers and Corrosion: Part 2 — Polyaniline on Aluminum Alloys

Abstract: The electrochemical behavior of conducting polyaniline coatings on various aluminum alloys subjected to immersion in dilute Harrison solution (035% ammonium sulfate [(NH4)2SO4], 005% sodium chloride [NaCl]) was studied Electrochemical impedance spectroscopy revealed that the charge-transfer resistance (Rct) of polyaniline-coated alloys increased as a function of immersion time Polyaniline-coated platinum did not exhibit a significant increase in impedance under similar conditions, indicating that an active metal in contact with the polyaniline is required for the observed increase in Rct A similar pattern of increasing Rct was observed for Alodine (Product A)-treated Al 7075T-6 (UNS A97075) alloys Mean current and mean potential values obtained from electrochemical noise measurements also suggest a substantial electrochemical interaction between the polyaniline and the aluminum alloy during the early stages of immersion Polarization experiments and opencircuit potential measurements reveal

Review of the Corrosion of Nickel-Based Alloys and Stainless Steels in Strongly Oxidizing Pressurized High-Temperature Solutions at Subcritical and Supercritical Temperatures

Abstract: The corrosion phenomena of nickel-based Alloy 625 (UNS N06625), which in the present content is representative of other nickel-based alloys and stainless steels in strongly oxidizing solut...

2000 F.N. Speller Award Lecture: Stress Corrosion Cracking in Pressurized Water Reactors Interpretation, Modeling, and Remedies

Abstract: The aging of water-cooled and moderated nuclear steam supply systems inevitably has given rise to many material corrosion problems of which stress corrosion cracking (SCC) is one of the mo...

Corrosion Fatigue Crack Initiation in Aluminum Alloys 7075 and 7050

Abstract: Mechanisms of corrosion fatigue crack initiation by pitting in high-strength, 7000-series aluminum alloys were studied The alloys used were Al 7075-T7351 (UNSA97075) and Al 7050-T7451 (UN

Oxides Formed on Titanium by Polishing, Etching, Anodizing, or Thermal Oxidizing

Abstract: Photoelectrochemistry (PEC), glancing angle x-ray diffraction (GAXRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) in synthetic salt water were uti...

Dianils: New and Effective Corrosion Inhibitors for Oil-Well Steel (N-80) and Mild Steel in Boiling Hydrochloric Acid

Abstract: Selected condensation products of aromatic aldehydes and p-phenylenediamine have been synthesized and evaluated as corrosion inhibitors for mild steel (MS) and oil-well steel (N-80) in 15% hydrochloric acid (HCl) at 105°C ± 2°C by the weight loss method. All the condensation products showed excellent performance. 2,4-dicinnamyledene aminophenylene (DCAP) was found to be the best corrosion inhibitor. It exhibited 99.75% inhibition efficiency (IE) for MS and 99.12% for N-80 steel at 5,000 ppm of inhibitor concentration. The potentiodynamic polarization studies carried out at room temperature on MS in 15% HCl containing 500 ppm of condensation products showed that all the investigated compounds were mixed type inhibitors, whereas 500 ppm DCAP on N-80 steel behaved predominantly as anodic inhibitors. The adsorption of all the condensation products was found to obey Temkin's adsorption isotherm.

Influence of pH and Chloride Concentration on the Pitting and Crevice Corrosion Behavior of High-Alloy Stainless Steels

Abstract: Localized corrosion resistance (pitting and crevice corrosion) of two high-alloy stainless steels (superduplex and superaustenitic) was studied in solutions with chloride concentrations of 200, 400, 600, and 6,000 ppm at pH values ranging from 2 to 6.5. Critical temperatures for pitting and crevice corrosion were calculated for these test media using electrochemical techniques (continuous current). From results obtained for cyclic polarization, the critical pitting temperature (CPT) and critical crevice temperature (CCT) of these materials in the different test media were determined. Under the tested conditions, the resistance of these materials to localized corrosion was very high. Only in test conditions of higher aggressivity (6,000 ppm Cl− and pH 6.5), pitting or crevice corrosion was observed. In those cases, values of pitting potential (Epit) and crevice potential (Ecre) showed little tendency to decrease with an increase in Cl− concentration, temperature, and pH. Moreover, the CPT of these...

An Electrochemical Approach to Predicting Long-Term Localized Corrosion of Corrosion-Resistant High-Level Waste Container Materials

Abstract: Lifetime predictions of containers used for the disposal of high-level radioactive waste (HLW) are necessary to determine the overall performance of a HLW repository. Failure of the contai...

Prediction of Stress Corrosion Cracking Susceptibility of Stainless Steels Based on Repassivation Kinetics

Abstract: Repassivation kinetics of rapidly scratched scars on the surface of type 304 (UNS S30400) stainless steel (SS) in a chloride solution was examined using an ampero-chronometric method. Its ...

Pigment-Derived Inhibitors for Aluminum Alloy 2024-T3

Abstract: Inhibitor characteristics of 27 compounds considered as possible replacements for chromate pigments in aerospace paint were investigated. These compounds were tested and screened in soluti...

Formation of Corrosion Products on Open and Confined Zinc Surfaces Exposed to Periodic Wet/Dry Conditions

Abstract: The formation of corrosion products was followed during the atmospheric corrosion of open and confined zinc surfaces exposed to periodic wet and dry conditions. The periodic wet and dry exposure consisted of the immersion of samples in sodium chloride (NaCl) solutions followed by exposure to laboratory air for different time periods. Phases of the corrosion products were identified by Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD), while the relative proportions of the corrosion products were determined by FTIR. Three main components were identified in the corrosion products on the zinc surfaces, namely zinc oxide (ZnO), hydrozincite (Zn5[OH]6[CO3]2), and simonkolleite (Zn5[OH]8Cl2·H2O). The wet/dry pattern of the exposure conditions was an important factor affecting the composition of the corrosion products for open zinc surfaces and zinc surfaces confined in crevices. Similar proportions of zinc oxide, simonkolleite, and hydrozincite were formed on both open and conf...

Migrating Corrosion Inhibitor Blend for Reinforced Concrete: Part 2— Inhibitor as Repair Strategy

Abstract: The efficiency of a migrating corrosion inhibitor in stopping or reducing corrosion of steel has been investigated in saturated (sat.) calcium hydroxide (Ca[OH]2) solutions and mortar. In solution, a slight decrease of the corrosion rate was found when the inhibitor blend (10%) was added after the onset of pitting corrosion. Investigation of the diffusion rate in mortar demonstrated the high mobility of the hydroxyalkylamine molecule in porous cement paste. Thus, it was assumed that it is, in principle, possible to obtain high inhibitor concentrations at the rebar to influence corrosion rate. However, on reinforced mortar samples showing chloride-induced pitting corrosion, no reduction of the corrosion rate could be detected after inhibitor application. The discrepancy between the observed high diffusion rate and the lack of corrosion mitigation was rationalized by the fact that only the diffusion of the volatile component of the inhibitor was measured. Migration of the nonvolatile component (car...

Corrosion of Iron Under Alternating Wet and Dry Conditions

Abstract: In-situ alternating current (AC) and direct current (DC) electrochemical techniques were used to determine the corrosion rate and corrosion potential of high-purity iron under alternate wet and dry conditions. Comparisons between DC electrochemical measurements and weight loss were conducted to verify the validity of the corrosion rate measurements. Identification of the corrosion products was performed using Raman spectroscopy. Corrosion products contained layers of iron oxides and oxyhydroxides. At low Cl− concentrations, corrosion products consisted of lepidocrocite (γ-FeOOH) and magnetite (Fe3O4). At higher Cl− concentrations, the formation of akaganeite (β-FeOOH) was observed. Corrosion rates and corrosion potentials fluctuated throughout the wet cycles depending on electrolyte layer thickness, ionic strength, and wetting cycle. Accelerated corrosion rates of high-purity iron, up to three times those observed under continuously immersed conditions, were the result of Fe(III) reduction in the...

Aqueous Corrosion Behavior of Weathering Steel and Carbon Steel in Acid-Chloride Environments

Abstract: Aqueous corrosion characteristics of carbon steel and weathering steel in aerated acid-chloride solutions were studied by using immersion weight loss tests, crevice corrosion tests, electr...

Effect of Cold Work and Processing Orientation on Stress Corrosion Cracking Behavior of Alloy 600

Abstract: Cold work accelerates stress corrosion cracking (SCC) growth rates in Alloy 600 (UNS N06600). However, the variation in crack growth rates generated from cold-worked material has been sign...

Effect of Thiosemicarbazones on Corrosion of Steel in Phosphoric Acid Produced by Wet Process

Abstract: Corrosion inhibition of steel in phosphoric acid (H3PO4) by thiosemicarbazide derivatives was studied using different chemical and electrochemical techniques. Protection efficiency up to 99% was obtained with small amounts (10−4 M) of cinnamaldehyde thiosemicarbazone (CTSCN). The order of increasing inhibition efficiency was correlated with the modification of the molecular structure of the inhibitors. Empirical kinetic relationship was obtained describing the experimental data obtained from the different compounds used in this investigation. Potentiodynamic polarization curves indicated that the compounds acted primarily as mixed-type inhibitors. Electrochemical impedance spectroscopy showed that the charge-transfer resistance increased and the capacitance of the double layer decreased with increasing the concentration of the inhibitor in the medium, confirming adsorption process mechanism. At high concentrations (> 104 M), the capacitance of the double layer leveled off since maximum double-lay...

2000 W.R. Whitney Award Lecture : Visualizing corrosion

Abstract: Using a broad-range pH indicator, the corrosion of Al and Al alloys in chloride-containing agar gels was studied. Distinct changes in pH were observed at low-pH anodic sites and at high-pH cathodes. There was a definite edge effect that occurred when gels were placed directly on the metal, which dominated the pattern of corrosion. Wet-abraded surfaces initially showed a general type of corrosion, whereas dryabraded surfaces showed localized corrosion under the gel. Pure Al, AA1100 (UNS A91110), AA2024 (UNS A92024), and AA5052 (UNS A95052) all showed pitting in contact with agar gels when the edge effect was prevented. Abraded AA7075 (UNS A97075) exhibited a filiform type of corrosion caused by high concentrations of corrosion product initiating corrosion ahead of the growing site.

Technical Note: CAHMT—A New and Eco-Friendly Acidizing Corrosion Inhibitor

Abstract: A new N- and S-containing heterocyclic compound, CAHMT, was synthesized and evaluated as a corrosion inhibitor for oil-well tubular steel (N-80) and mild steel (MS) at 105°C ± 2°C by the weight loss method. Potentiodynamic polarization measurements were carried out at room temperature for both steels in the presence of propargyl alcohol (PA) and CAHMT. Results indicate that the CAHMT is a mixed-type inhibitor while PA is predominantly cathodic. The adsorption of the inhibitors on N-80 steel and MS surface from 15% hydrochloric acid (HCl) has been found to obey Temkin's adsorption isotherm. The efficiency of CAHMT has been found to be comparable with that of PA, a standard corrosion inhibitor for MS in boiling HCl.

Influence of overaging treatment on localized corrosion of Al 6056

Abstract: The influence of T78 overaging treatment on the corrosion behavior of Al 6056 (UNS A96056) in 1 M sodium chloride (NaCl) solution was investigated. The overaged alloy presented the same localized corrosion mechanisms as Al 6056-T6. However, Al 6056-T78 coarse intermetallic Al-Mg-Si-containing particles were found to be more reactive than those in the Al 6056-T6 alloy and were nucleation sites for pits. Pitting and intergranular corrosion were dependent upon each other; intergranular corrosion nucleated on pit walls. A quantitative study showed that T78 overaging of Al 6056 offered a better resistance to intergranular corrosion compared to T6 peak-aging treatment. The overaged alloy will be able to replace the traditional Al 2024 (UNS A92024) because of the efficiency of this overaging treatment

An Overview: Vapor Phase Corrosion Inhibitors

Abstract: When present as vapors, certain organic compounds offer inhibition against the corrosion of ferrous and nonferrous materials. The inhibitors include aliphatic, aromatic, cyclohexylamines, aminonitrobenzoates, heteroalkylated lower amines, etc. The mechanism of inhibition offered by these compounds was discussed and an unified mechanism was presented. Various methods of evaluating inhibition efficiency were discussed with a special reference to surface film characterization techniques. Methods of application of the vapor phase inhibitors and their industrial uses also were presented.