Corrosion Of X80 Pipeline Steel Research Articles

Influence of Xinjiang Saline Soil on Corrosion of X80 Pipeline Steel

A large-scale gas transmission pipeline project will pass through typical saline soil areas in Xinjiang, China, to find out the influence of the saline soil on the long-distance pipeline in this area, this paper investigates the corrosive behavior of X80 pipeline steel embedded in saline soil with multiple corrosion intensities. Firstly, NaCl, Na2SO4, NaHCO3, and deionized water were used to simulate the saline soil with different corrosion intensities, and then the corrosion test of X80 steel was carried out. A scanning electron microscope was used to observe the X80 steel before and after corrosion. Finally, the weight loss method was used to calculate the corrosion rate, and the corrosive behavior of X80 pipeline steel in Xinjiang saline soil environment was analyzed. The results show that: (1) X80 steel is susceptible to pitting corrosion in the saline soil environment; (2) the rate and level of corrosion were mainly related to the content of Cl− and SO4 2−. The greater the content, the stronger the pipeline is corroded; (3) the rate and level of corrosion were positively correlated with the corrosion intensities of saline soils.

Effect of yeast extract on microbiologically influenced corrosion of X70 pipeline steel by Desulfovibrio bizertensis SY-1

Microbiologically influenced corrosion (MIC) is a complicated process that happens ubiquitously and quietly in many fields. As a useful nutritional ingredient in microbial culture media, yeast extract (YE) is a routinely added in the MIC field. However, how the YE participated in MIC is not fully clarified. In the present work, the effect of YE on the growth of sulfate reducing prokaryotes (SRP) Desulfovibrio bizertensis SY-1 and corrosion behavior of X70 pipeline steel were studied. It was found that the weight loss of steel coupons in sterile media was doubled when YE was removed from culture media. However, in the SRP assays without YE the number of planktonic cells decreased, but the attachment of bacteria on steel surfaces was enhanced significantly. Besides, the corrosion rate of steel in SRP assays increased fourfold after removing YE from culture media. MIC was not determined for assays with planktonic SRP but only for biofilm assays. The results confirm the effect of YE on D. bizertensis SY-1 growth and also the inhibitory role of YE on MIC.

Corrosion under insulation of pipeline steel in groundwater containing sulphate-reducing bacteria

ABSTRACT Corrosion under insulation is a major economic concern in the safe operations of water, oil and gas steel pipes. Herein, the external corrosion of X80 pipeline steel was examined beneath a disbonded insulation in groundwater containing sulphate-reducing bacteria (SRB). The results show that the steel under the insulation exhibited different electrochemical behaviour from the uninsulated sample in the bulk solution. A galvanic effect was detected between the steel under insulation and the uninsulated sample. Spectroscopic analysis reveals the rust layer of the insulated steel immersed in the SRB-inoculated groundwater was enriched by FeS from microbial metabolism. The steel under insulation recorded severe localised perforation, while corrosion severity was reduced on the uninsulated sample. Diffusion of ions, film development and insulation degradation played important roles in steel corrosion.

Inhibition Effect of Pseudomonas stutzeri on the Corrosion of X70 Pipeline Steel Caused by Sulfate-Reducing Bacteria.

Microbiologically influenced corrosion (MIC) is a common phenomenon in water treatment, shipping, construction, marine and other industries. Sulfate-reducing bacteria (SRB) often lead to MIC. In this paper, a strain of Pseudomonas stutzeri (P. stutzeri) with the ability to inhibit SRB corrosion is isolated from the soil through enrichment culture. P. stutzeri is a short, rod-shaped, white and transparent colony with denitrification ability. Our 16SrDNA sequencing results verify the properties of P. stutzeri strains. The growth conditions of P. stutzeri bacteria and SRB are similar, and the optimal culture conditions are about 30 °C, pH 7, and the stable stage is reached in about seven days. The bacteria can coexist in the same growth environment. Using the weight loss method, electrochemical experiments and composition analysis techniques we found that P. stutzeri can inhibit the corrosion of X70 steel by SRB at 20~40 °C, pH 6~8. Furthermore, long-term tests at 3, 6 and 9 months reveal that P. stutzeri can effectively inhibit the corrosion of X70 steel caused by SRB.

The synergistic effect of temperature, H2S/CO2 partial pressure and stress toward corrosion of X80 pipeline steel

In this work, the H2S / CO2 coexistence environment was simulated in a high-temperature and high-pressure reactor. The influence of H2S/CO2 partial pressure (0/1.2, 0.7/1.2 and 2.0/1.2 MPa), temperature (50, 100 and 150 °C) and applied stress (30%, 70% and 90% σs) on the corrosion rates of natural gas pipeline steel X80 was investigated by the weight loss measurements combined with the SEM, EDS and XRD techniques. The results show that the corrosion of X80 steel under pure CO2 condition is much more serious than that under H2S/CO2 coexistence. The corrosion stability of amorphous film can be improved by the formation of amorphous Cr (OH)3 in the presence of H2S, which provides better surface protection than in the pure CO2 environment. The corrosion of X80 steel in H2S/CO2 coexistence is dominated by H2S corrosion and the corrosion rates increase with the increase of H2S partial pressure. The corrosion rate firstly increases with the increase of temperature, and the highest corrosion rate occurs near 100 °C under the existing experimental conditions. After that, the corrosion rate began to decrease. The applied stress significantly affects the corrosion rate, and high stress speeds up the corrosion process of X80 steel in the H2S/CO2 coexistence environment.

Effect of Pseudomonas sp. on simulated tidal corrosion of X80 pipeline steel

Microbiologically influenced corrosion of pipeline steel in seawater has long been concerned by scholars all over the world, but there were few reports on the microorganism effect on marine tidal corrosion of steels. In this work, the effect of Pseudomonas sp. on static tidal corrosion of X80 pipeline steel were systematically studied using weight-loss, Fourier transform infrared spectroscopy (FTIR), electrochemical measurements, scanning electron microscopy (SEM) and ultra-deep field 3D microscope. The results manifested that after 720 h exposure to the marine tidal environment, the sessile Pseudomonas sp. counts multiplied with the elevation increase. The corrosion style of the steel in the inoculated environment was mainly localized corrosion. As a consequence of the higher bacteria number, the corrosion rate, pit depth and corrosion product thickness collectively enhanced. Pseudomonas sp. significantly accelerated uniform and localized corrosion of the steel in the marine tidal zone, and the acceleration role enhanced with the steel elevation in the tidal zones.

Mechanistic investigations of corrosion and localized corrosion of X80 steel in seawater comprising sulfate-reducing bacteria under continuous carbon starvation

Sulfate-reducing bacteria (SRB) corrosion is one of the main reasons leading to the service failure of engineering materials in the marine environment. An understanding of SRB corrosion especially under continuous organic carbon starvation is required. In this work, SRB corrosion of X80 pipeline steel under continuous organic carbon starvation was studied using mass loss, electrochemical measurements, and surface analysis. The effects of initial SRB concentrations on steel corrosion were also studied and discussed. The results indicated that more than 99% population of SRB die after 21 d of testing in various conditions, but there are still amounts of SRB survivors. SRB survivors with continued organic carbon starvation have a better adaptive ability and accelerated steel corrosion. Both the uniform and localized corrosion rates are also proportional to the initial SRB concentration as well as SRB survivors. The localized corrosion rate and density of corrosion pits of specimen corresponding to an initial SRB count of 108 cells/mL reach bigger values of (0.693 ± 0.114) mm/y and (1.94 ± 0.39)×104 pits/cm2, respectively, which are induced by the combination of the sessile and planktonic SRB.

The effect of riboflavin on the microbiologically influenced corrosion of X80 Pipeline Steel by Escherichia Coli

The effect of riboflavin on the microbiologically influenced corrosion of X80 Pipeline Steel by Escherichia Coli

Accelerated sulfate reducing bacteria corrosion of X80 pipeline steel welded joints under organic carbon source starvation

Sulfate-reducing bacteria (SRB) corrosion of X80 steel welded joint under organic carbon source starvation was investigated in the paper. The results showed that the number of planktonic cells is much less than that of sessile cells after 720 h immersion. The number of sessile cells in the base metal (BM) in the medium with 1% carbon source is the largest. Starving SRB cells accelerated simultaneously the uniform corrosion and localized corrosion of the welded joints, and the acceleration effect on the latter was much higher than that of the former. In all mediums, the density and average depth of pits in the BM and weld zone (WZ) were much larger than those in the heat affected zone (HAZ). SRB corrosion of the welded joint was strongly selective, and organic carbon source starvation further enhanced the selectivity.

Effects of the IR Drop on the Electrochemical Corrosion of X80 Pipeline Steel in Different Solutions

Polarization curves are popularly used in many investigations; however, some wrong results are obtained when inexperienced researchers do not deeply understand electrochemical processes. In this study, the effects of the IR drop (Deviation due to I (current) and R (resistance)) and scanning direction on polarization curves were investigated. Three different test methods were used to test the polarization curve of X80 pipeline steel in five kinds of solutions. The different scanning directions led to differences in the cathodic polarization curves. In addition, the effect of IR drop on the Tafel curve in acidic solutions is significantly greater than in neutral and alkaline solutions. There is a large effect of the IR drop on shapes and fitting results of polarization curves in acidic solutions, and the IR drop must be considered for the fitting of curves. Scanning direction has an influence on the shape of polarization curves when a layer of corrosion products is formed on the steel surface, and a novel two-electrode coupon was introduced to solve this problem.

Understanding the effect of tensile stress on erosion-corrosion of X70 pipeline steel

The pipelines in the oil and gas industry may simultaneously suffer damage from tensile stress and erosion at the internal surface, which could cause the pipeline failure easily. In this work, the combined effect of tensile stress and erosion on the corrosion of X70 pipeline steel was studied in a loop system coupled with a stress loading device. The general corrosion and localized corrosion under the combination of tensile stress and erosion was comprehensively investigated using finite element simulation analysis, potentiodynamic polarization curve, electrochemical impedance spectroscopy, scanning electron microscope as well as 3D ultra-depth microscope. The results show that both tensile stress and erosion can promote general corrosion independently. Furthermore, the combination of tensile stress and erosion can generate a synergistic effect on general corrosion of steels through reducing the compactness of corrosion products layer, accelerating the mass transfer process and improving the reaction activity of the steel, with a changed corrosion current density of 37.54 μA/cm2, even exceeding the influence of tensile stress (17.76 μA/cm2). For localized corrosion, erosion can enhance the inside-out diffusion of metal cations in the metastable pit and dilute the pit anolyte, while tensile stress may generate stress concentration on corrosion defects. Therefore, erosion shows a suppression on localized corrosion, but an enhancement effect from tensile stress.

Selected corrosion of X80 pipeline steel welded joints induced by Desulfovibrio desulfuricans

Sulfate-reducing bacteria (SRB) corrosion of X80 pipeline steel welded joints has been investigated. The larger diameter, deeper depth and higher density of the corrosion pits were detected in the heating affected zone (HAZ) than in the base metal (BM) and weld zone (WZ) in the sterile medium. However, in the inoculated medium, Desulfovibrio desulfuricans (D. desulfuricans) tended to attach primarily to the BM and WZ, and increased their local corrosion sensibilities. D. desulfuricans disliked to attach to the HAZ surface and only non-uniform corrosion dominated on the surface, which was an important phenomenon in D. desulfuricans corrosion of pipeline steel.

Accelerated tidal corrosion of X80 pipeline steel by Desulfovibrio desulfuricans

Tidal corrosion of X80 pipeline steel in the inoculated marine tidal environment was investigated using weight-loss, SEM/EDS and electrochemical measurements. The results showed D. desulfuricans accelerated the tidal corrosion of the steel and the acceleration effect increased with the altitude of the specimen in tidal zones. The corrosion morphology of the specimens in all zones was non-uniform with some low-shallow corrosion pits in it, and the diameter and depth of the low-shallow pits increased with the altitude of the specimen. The D. desulfuricans activity, distribution of the S-containing compounds and wet/dry process were conjointly responsible for the accelerated tidal corrosion.

Galvanic corrosion of X80 pipeline steel double‐sided submerged arc welded joints in simulated near‐neutral soil solution

AbstractThe corrosion behaviors of double‐sided submerged arc welded joints in X80 pipeline steel with or without coupling were studied in simulated near‐neutral soil solution. The galvanic effect in the welded joint was evaluated by corrosion morphology, corrosion depth, and electrochemical measurements. When the weld metal (WM), heat affected zone (HAZ) and base metal (BM) samples were immersed in the solution isolated, pitting holes occurred around the martensite/austenite constituents in the weld metal and base metal samples, which was mainly due to the preferential corrosion of ferrite. However, no pitting holes occurred in the heat affected zone due to small specific surface area induced by the coarse martensite/austenite constituents. Polarization curves results showed that the corrosion current density of coupled base metal was 5 times larger than that of isolated base metal and the corrosion current density of isolated heat affected zone was three times larger than that of coupled heat affected zone after 48 h immersion. The corrosion current density of coupled heat affected zone was one order of magnitude lower than that of coupled weld metal and base metal. When the welded joint was exposed to an aggressive environment, the base metal samples were determined to be the most anodic zone while the heat affected zone was the most cathodic zone. The weld metal underwent little galvanic interaction, as its corrosion potential was close to the coupled potential. In addition, the galvanic effect among the welded joints decreased with the prolong of immersion time.

Biologically competitive effect of Desulfovibrio desulfurican and Pseudomonas stutzeri on corrosion of X80 pipeline steel in the Shenyang soil solution

In this paper, we have investigated the corrosion mechanism of X80 carbon steel in the presence of nitrate reducing bacteria (NRB), sulfate reducing bacteria (SRB) or both in the Shenyang soil solution. The results show that both SRB and NRB increase the corrosion rate of steel specimens and cause pitting corrosion of steel. Electrochemical tests and weight-loss data show that the addition of NRB in the SRB-containing environment leads to the reduction of corrosion. The thermodynamic analyses confirm the competitive advantage of NRB for the nutrients (organic carbon sources and irons) and the chemical oxidation of ferrous sulfide by nitrite, which results in a mitigation in the microbiologically influence corrosion (MIC) of SRB.

Corrosion of steel in a CO2-containing solution droplet generated in wet gas pipelines studied by scanning Kelvin probe

A scanning Kelvin probe (SKP) was used to study corrosion of X52 pipeline steel under a CO2-containing solution droplet simulating the water condensate generated in interior of wet gas pipelines. The Volta potential measured by SKP was indicative of the feature of corrosion occurring under the droplet. Three potential zones were observed from the droplet center towards the transition and the side of the droplet, which were -0.1 V, -0.4 V and 0.1 V (Kelvin probe, kp), respectively, after 4 h of testing. The droplet side had the highest Volta potential, which was attributed to corrosion scale generation and precipitation due to a limited solution volume and achieved solubility limit of FeCO3 scale. The transition zone possessed the most negative Volta potential due to a higher corrosion activity than the droplet center with more supply and dissolution of CO2, while the droplet center had the thickest solution. The SKP measurements could estimate the volume evolution of the solution droplet with time at a relatively accurate scale. The solution droplet could maintain its topographic feature, i.e., a spherical cap shape, within 4 h of testing in this work. The increase in droplet concentration due to solution evaporation during testing affected the Volta potential, but slightly only.

Effect of uniaxial elastic stress on corrosion of X80 pipeline steel in an acidic soil solution containing sulfate-reducing bacteria trapped under disbonded coating

The effect of elastic stress on corrosion of X80 steel in an acidic soil solution containing sulfate-reducing bacteria (SRB) trapped under a simulated disbonded coating was investigated. The SRB numbers at the coating holiday after 14 days were approximately 106 cells/mL, and they were higher than those in the simulated disbonded coating region. The stressed coupons underwent more severe SRB corrosion and pitting at the same locations under the simulated disbonded coating due to the mechanochemical effect. These results indicated that the pitting process was affected by the applied elastic stress in the X80 steel.

Effect of Glutaraldehyde on Corrosion of X80 Pipeline Steel

Glutaraldehyde (GA) is widely employed as a biocide to control microbiologically influenced corrosion in oil fields and industrial water treatment. It might be corrosive to metal. In this study, the effect of glutaraldehyde on the corrosion behavior of X80 pipeline steel was investigated using electrochemical measurement, weight-loss tests and scanning electron microscope (SEM). The weight-loss and electrochemical data show that GA accelerates the corrosion of samples under aerobic conditions, but just slightly influences the corrosion of steel under anaerobic conditions. The results showed that the glutaraldehyde has a minor effect on the corrosion of steel under anaerobic conditions.

Effect of alternating current and nitrate reducing bacteria on corrosion of X80 pipeline steel in Shenyang soil solution

In this work, electrochemical measurements and surface analysis techniques were used to investigate the effects of alternating current (AC) and nitrate reducing bacteria (NRB) on the corrosion behavior of X80 pipeline steel in the Shenyang soil extract solution. Either AC or NRB increases the corrosion rate of X80 steel samples, and the combination of AC and NRB can make the corrosion rate reach about 16.5 times of that without AC and NRB. Confocal laser scanning microscopy (CLSM) images show that the maximum pitting depth is up to 38.3 μm through the synergistic effect of AC and NRB. The data in this paper strongly confirms that AC and NRB synergistically accelerate the pitting formation of X80 pipeline steel, and lead to the generation of deeper and larger pits.

Laboratory Investigation of Microbiologically Influenced Corrosion of X80 Pipeline Steel by Sulfate-Reducing Bacteria

Laboratory Investigation of Microbiologically Influenced Corrosion of X80 Pipeline Steel by Sulfate-Reducing Bacteria