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1.
Micro-electrochemical characterization of corrosion of welded X70 pipeline steel in near-neutral pH solution 总被引:4,自引:0,他引:4
G.A. Zhang 《Corrosion Science》2009,51(8):1714-1724
The local corrosion behavior of welded X70 pipeline steel in near-neutral pH solution was studied by micro-electrochemical measurements, including scanning vibrating electrode and local electrochemical impedance spectroscopy. The microstructure of the welded steel was observed by optical microscopy and scanning electron microscopy. It is demonstrated that the microstructure of weld metal consists of acicular ferrite and grain boundary ferrite, while that of heat-affected zone is a mixture of acicular ferrite, bainitic ferrite and a few martensite/austenite microconstituents. The microstructure of base steel is typically ferrite and pearlite. Electrochemical corrosion mechanism of welded X70 steel does not experience change upon hydrogen-charging, or stressing, or both. Hydrogen-charging is capable of enhancing the local anodic dissolution of the steel. The resistance of corrosion product layer decreases with hydrogen-charging, and heat-affected zone has the largest dissolution current upon hydrogen-charging. The increase of applied stress enhanced the anodic dissolution of welded X70 steel, especially the heat-affected zone, in near-neutral pH solution. Maximum current is observed in heat-affected zone, and increases with the increase of applied stresses. The total synergistic effect of hydrogen-charging (10 mA/cm2) and applied stress (550 MPa) on anodic dissolution of welded X70 steel in near-neutral pH solution is determined to be within the range of 5.7 and 6.5, with a maximum value encountering in heat-affected zone. 相似文献
2.
Occurrence of stress corrosion cracking of pipelines under a near-neutral pH condition depends on the synergism of stress, hydrogen and anodic dissolution at the crack tip of the steel. In this work, micro-electrochemical techniques, including localized electrochemical impedance spectroscopy and scanning vibrating electrode technique, were used to characterize quantitatively the synergistic effects of hydrogen and stress on local dissolution at crack-tip of a X70 pipeline steel in a near-neutral pH solution. Results demonstrate that, upon hydrogen-charging, the anodic dissolution of the steel is enhanced. The resistance of the deposited corrosion product layer depends on the charging current density. There is a non-uniform dissolution rate on the cracked steel specimen, with a highest dissolution current density measured at crack-tip. For a smooth steel specimen, the synergistic effect factor of hydrogen and stress is equal to 5.4, and the total effect of hydrogen and stress on anodic dissolution of the steel is 7.7. In the presence of a crack, the hydrogen effect factor, stress effect factor and the synergistic effect factor are approximately 4.3, 1.3 and 4.0, respectively. The total effect factor is up to 22.4, which is very close to the 20 times of difference of crack growth rate in pipelines in the presence and absence of the hydrogen involvement recorded in the field. 相似文献
3.
Stress corrosion cracking behaviour of API-5L-X52 steel under cathodic protection in near-neutral and high pH conditions was studied using slow strain rate test method and electrochemical measurements. The slow strain rate test showed ductile and brittle fracture feature at low and high applied potentials, respectively. In order to identify the mechanism contributes in stress corrosion cracking; the electrochemical potentiodynamic polarisation test was done at fast and slow sweep rate. The results revealed that at near-neutral pH condition the anodic dissolution at crack tip was the dominant mechanism. While at high pH medium, the hydrogen based mechanism was dominant. 相似文献
4.
Rong Wang 《Corrosion Science》2009,51(12):2803-2810
Effects of hydrogen on the fracture toughness of a X70 pipeline steel were investigated in the cases of hydrogen pre-charging and dynamic hydrogen charging in 0.5 mol/L H2SO4 solution under slow strain rate tensile testing. Under the hydrogen pre-charging, the fracture toughness decreased in a linear relationship with the hydrogen concentration as the hydrogen concentration was more than 1 ppm in weight. The fracture surfaces were characteristic of dimples. Under the dynamic hydrogen charging, the fracture toughness for hydrogen-induced cracking decreased linearly with logarithm of the hydrogen concentration without stress. The hydrogen-induced fracture had the appearance of cleavage facets. 相似文献
5.
Influence of pH on the nitrite corrosion inhibition of reinforcing steel in simulated concrete pore solution 总被引:1,自引:0,他引:1
Measurements of corrosion rate of reinforcing steels have been carried out in solutions simulating electrolytic chloride environments in corrosion pits in the propagation period with sodium nitrite. A significant corrosion inhibition has been observed at relatively low chloride contents of 0.045 M due to the presence of nitrite in these systems, but its efficiency decreases when the pH is reduced. The corrosion intensity seems to be related to the [Cl−]/[OH−] ratio. Three different pH regions from acid to alkaline have been observed in terms of corrosion activity. An explanation on the behaviour of nitrite at different pH is given. 相似文献
6.
Micro-electrochemical characterization of corrosion of pre-cracked X70 pipeline steel in a concentrated carbonate/bicarbonate solution 总被引:1,自引:0,他引:1
G.A. Zhang 《Corrosion Science》2010,52(3):960-968
The electrochemical corrosion behavior of a stressed, pre-cracked X70 pipeline steel was studied in a bicarbonate/carbonate solution by electrochemical and micro-electrochemical measurements, numerical calculation and surface analysis technique. The effects of stress and potential on passivity, corrosion and electrochemical behavior of the steel at crack-tip were mechanistically determined. It was found that the passive film formed at crack-tip was less stable than that formed in the region ahead of the crack. Moreover, the crack-tip is more susceptible to pitting corrosion than other region of the specimen. The applied stress enhances the anodic dissolution of the steel. In particular, the stress concentration at crack-tip further increases the local anodic dissolution rate. The enhancement of the anodic dissolution of the steel at crack-tip is also resulted from the formation of a galvanic couple, i.e., the crack-tip as an anode and the surrounding region as a cathode. 相似文献
7.
Environmentally assisted cracking mechanism of pipeline steel in near-neutral pH groundwater 总被引:1,自引:0,他引:1
A modified Devanathan dual cell was used in environmentally assisted cracking (EAC) tests to independently control the concentration of dissolved hydrogen and anodic current density. The experimental evidence indicates that the corrosion may reduce the micro-hardness of steel, suggesting a dissolution-induced degradation of the mechanical properties in the surface layer. An EAC model is described in which surface micro-plastic deformation can be enhanced by the dissolved hydrogen and anodic dissolution, and plays a crucial role in cracking processes. The model can provide a reasonable prediction for the dependence of the cracking resistance of pipeline steel on the applied potential. 相似文献
8.
Yongwang Kang Weixing Chen Richard Kania Gregory Van Boven Robert Worthingham 《Corrosion Science》2011,(3):968-975
The objective of this investigation was to understand the role of crack dimension, hydrogen, room-temperature creep and loading procedure on crack growth during hydrostatic testing of pipeline steels in near-neutral pH aqueous soil environments. Crack growth was found during hydrotesting, but was not linearly related to the stress intensity factor at the crack tip. Crack growth is mainly driven through the internal-hydrogen-assisted-cracking mechanism, instead of the hydrogen-environmental-assisted-cracking mechanism. Excessive plastic deformation induced by room-temperature creep prior to hydrotesting reduces crack advance during hydrotesting. Lower loading rate generally induces larger crack growth by hydrostatic loading. More crack growth occurs during loading in high stress regime. 相似文献
9.
Stress corrosion cracking initiation under the disbonded coating of pipeline steel in near-neutral pH environment 总被引:1,自引:0,他引:1
A novel test setup has been used in this study to simulate stress corrosion cracking initiation under a disbonded coating on an X-65 pipeline steel. In this setup, the synergistic effects of cyclic loading, cathodic protection and soil solution environment under disbonded coatings have been considered. When the X-65 pipeline steel was exposed to the test environment, there existed a wide range of corrosion products on the steel surface in the gradient of cathodic protection. Increasing the test time and the maximum stress increased the possibility of stress corrosion cracking initiation in regions with a high susceptibility to pitting corrosion. 相似文献
10.
B.R. Tian 《Corrosion Science》2008,50(3):773-779
Oil sand slurry hydrotransport pipelines are experiencing serious corrosion and erosion. In this work, rotating disk electrode technique was used to study the effects of fluid hydrodynamics on corrosion of X-65 steel in the simulated oil sand slurry by potentiodynamic polarization curve and electrochemical impedance spectroscopy measurements. In the absence of sands, the cathodic polarization current increases with the increasing electrode rotating speed due to the accelerated oxygen diffusion and reduction. However, the anodic polarization current decreases because of the improved oxidation of the steel. Although the oxygen diffusivity increases with temperature, the resultant oxidation of steel by oxygen is not sufficient to offset the enhanced reactivity of steel at an elevated temperature. The presence of oils is believed to form a layer of oily phase on the steel surface, facilitating the cathodic reduction of oxygen and inhibiting dissolution of the steel. With the increasing sand content and size in the solution, the corrosion of steel is enhanced. 相似文献
11.
A corrosion mechanism has been developed to describe tubercle formation along pipeline steels during successive anaerobic–aerobic cycles. Small concentrations of O2 under nominally anaerobic conditions can lead to the separation of anodes and cathodes. Under subsequent aerobic conditions localized corrosion is then promoted by O2 reduction on the general magnetite-covered surface. Subsequently, the conversion of magnetite to maghemite passivates the general surface, and focuses corrosion within one major tubercle-covered pit. On switching from aerobic to anaerobic conditions, corrosion is temporarily supported by the galvanic coupling of lepidocrocite (γ-FeOOH) reduction (to γ-Fe-OH·OH) to steel dissolution primarily within the tubercle-covered pit. 相似文献
12.
The inhibition effect of two pyrazine derivatives of 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) was studied by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results show that both AP and ABP are good inhibitors, and inhibition efficiency follows the order: ABP > AP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves show that two pyrazine derivatives act as mixed-type inhibitors. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. 相似文献
13.
Inhibitory action of aqueous coffee ground extracts on the corrosion of carbon steel in HCl solution 总被引:1,自引:0,他引:1
Vanessa Vasconcelos Torres Roberto Salgado Amado Camila Faia de Sá Tatiana Lopez Fernandez Carlos Alberto da Silva Riehl Alexandre Guedes Torres Eliane D’Elia 《Corrosion Science》2011,(7):2385-2392
The effects of aqueous extracts of spent coffee grounds on the corrosion of carbon steel in a 1 mol L−1 HCl were examined. Two methods of extraction were studied: decoction and infusion. The inhibition efficiency of C-steel in 1 mol L−1 HCl increased as the extract concentration and temperature increased. The coffee extracts acted as a mixed-type inhibitor with predominant cathodic effectiveness. In this study, the adsorption process of components of spent coffee grounds extracts obeyed the Langmuir adsorption isotherm. The chlorogenic acids isolated do not seem to explain the corrosion inhibition observed during the use of the coffee extracts. 相似文献
14.
Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine 总被引:2,自引:0,他引:2
The behavior of the Schiff base N,N′-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1 mol L−1 HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the inhibitors studied. The results obtained in the presence of Salen were similar to those obtained in the presence of the salicylaldehyde and ethylenediamine mixture, showing that in acid medium the Salen molecule undergoes hydrolysis, regenerating its precursor molecules. 相似文献
15.
Sodium tungstate (Na2WO4) as a corrosion inhibitor of cold rolled steel (CRS) in peracetic acid (PAA) solution was investigated by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). All the data obtained from the experiments indicate that Na2WO4 is capable of inhibiting the corrosion of CRS in PAA solution. Polarization data show that Na2WO4 behaves as an anodic type inhibitor in PAA solution. Adsorption of Na2WO4 is found to follow the Temkin adsorption isotherm. The calculated free energy of adsorption (ΔGads) probably indicates that both physical adsorption and chemical adsorption may take place in the adsorption process. 相似文献
16.
The inhibition effect of methyl violet (MV) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20-50 °C was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that MV is an excellent inhibitor even with very low concentration, and the adsorption of MV on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that MV behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of MV is also evidenced by SEM. 相似文献
17.
The inhibition effect of nitrotetrazolium blue chloride (NTBC) on the corrosion of cold rolled steel (CRS) in 0.5 M H2SO4 was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that NTBC is a good inhibitor, and the adsorption of NTBC on CRS surface obeys Langmuir adsorption isotherm. Polarization curves show that NTBC acts as a mixed-type inhibitor. EIS spectra consist of large capacitive loop at high frequencies followed by a small inductive one at low frequency values, and charge transfer resistance increases with the inhibitor concentration. 相似文献
18.
Erosion–corrosion (E–C) of X-65 pipe steel was investigated in a simulated oil–sand slurry through an impingement jet system. Measurements of weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy combined with optical microscopy observation were performed to determine the synergism of corrosion and erosion in E–C of steel. It was found that passivity of the steel developed in static oil–water emulsion cannot be maintained in the flowing fluid due to the enhanced activity of the steel upon impingement of the emulsion/slurry. The effect of slurry impact angle on E–C of steel is complex, depending on the magnitude and synergism of shear stress and normal stress exerting on the electrode surface, enhancing the steel E–C by degrading the oxide film formed on the steel surface. There is a synergism of corrosion and erosion in E–C of steel. The contributions of corrosion and erosion to E–C rate of the steel in oil–sand slurry rank approximately 30% and 70%, respectively. Erosion dominates the E–C of X-65 steel in oil–sand slurry. 相似文献
19.
Blue tetrazolium as a novel corrosion inhibitor for cold rolled steel in hydrochloric acid solution 总被引:1,自引:0,他引:1
The inhibition effect of blue tetrazolium (BT) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20 °C was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that BT is a very good inhibitor, and the adsorption of BT on CRS surface obeys Langmuir adsorption isotherm. Polarization curves reveal that BT acts as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BT is also evidenced by SEM images. 相似文献
20.
The synergistic inhibition effect of rare earth cerium(IV) ion (Ce4+) and sodium oleate (SO) on the corrosion of cold rolled steel (CRS) in 3.0 M phosphoric acid (H3PO4) has been investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The results reveal that SO has a moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. Ce4+ has a poor effect. However, incorporation of Ce4+ with SO improves the inhibition performance significantly, and exhibits synergistic inhibition effect. SO acts as a cathodic inhibitor, while SO/Ce4+ mixture acts as a mixed-type inhibitor. 相似文献