Corrosion Behavior Of X80 Steel Research Articles

Effect of Hydrostatic Pressure on Corrosion Behavior of X70 Steel in Simulated Sea Water

Effect of Hydrostatic Pressure on Corrosion Behavior of X70 Steel in Simulated Sea Water

Study on corrosion behavior of X80 steel under stripping coating by sulfate reducing bacteria

BackgroundAt present, microorganism has been considered as important factors that threaten to buried pipelines with disbonded coatings. Aiming at the problem of unknown corrosion mechanism of sulfate-reducing bacteria (SRB), a series of studies have been carried out in this paper. Spectrophotometer and fluorescent labeling technology are used to study the growth and attachment of SRB in the simulated soil solution. The corrosion behavior of X80 pipeline steel with or without SRB was researched by electrochemical methods such as open circuit potential, dynamic potential polarization curve, and electrochemical impedance spectroscopy. The microscopic morphology of the corrosion products on the surface was observed with a scanning electron microscope (SEM), and the element content of the corrosion products on the surface of the sample after corrosion was observed using X-ray energy spectrum (EDS) analysis.ResultsThe results showed that the growth and reproduction of SRB caused the pH of the soil simulated solution to increase, which may promote the corrosion of X80 steel. In addition, the cathode reaction of X80 steel in a sterile environment is the reduction of H+, and the main corrosion product is iron oxide. When the soil simulation solution contains SRB, the cathodic reaction is controlled by both H+ reduction and sulfide depolarization reactions, and FeS appears in the corrosion products.ConclusionAlthough the life cycle of SRB is only about 14 days, the corrosion of X80 steel is greatly promoted by SRB, and even causes corrosion perforation, which will bring huge economic losses and serious safety hazards.

Effect of Cathodic Polarization on Corrosion Behavior of X65 Steel in Seawater Containing Iron-oxidizing Bacteria

Effect of Cathodic Polarization on Corrosion Behavior of X65 Steel in Seawater Containing Iron-oxidizing Bacteria

Corrosion behavior of X65 steel at different depths of pitting defects under local flow conditions

The electrochemical corrosion behavior and the development mechanism of the local corrosion of X65 steel under different defect depths were studied by using macroscopic electrochemical measurements and characterization techniques. A CO2-saturated NACE solution was used to study electrochemical corrosion characteristics in the single-phase flow-accelerated corrosion test loop system. Changes in the flow characteristic around the defects at different depths were characterized by COMSOL. The results indicated that samples with lower depth defects tend to deepen towards the radial direction both in the deep defects and shallow defects. Moreover, the upper and trailing edge of the defect has a tendency to deepen and expand the region of the defect under the influence of higher turbulent kinetic energy (TKE) and the shearing rate.

A synergistic effect of dissolved oxygen, $$HCO_3^-$$, and Cl− on the electrochemical corrosion behavior of X70 pipeline steel in the oilfield soil environment

The pipeline corrosion phenomenon in the Liaohe oilfield has become severe in recent years, and X70 steel has been extensively employed as a high-strength pipeline material in this oilfield. Therefore, in this study, the electrochemical corrosion of X70 steel in the simulated Liaohe oilfield soil solution was investigated under the combined action of dissolved oxygen (DO), $$HCO_3^-$$ , and Cl−. The corrosion behavior of X70 steel was examined by both the orthogonal test and the fitting analysis. It was found that DO, $$HCO_3^-$$ , and Cl− had profound influences on the corrosion behavior of X70 steel. When concentrations of $$HCO_3^-$$ , and Cl− were stable in the solution, both current corrosion density and corrosion rate gradually increased with the increasing DO concentration. When concentrations of DO and Cl− were constant, the current corrosion density also increased with the increasing $$HCO_3^-$$ concentration. When concentrations of DO and $$HCO_3^-$$ were constant, the current corrosion density decreased significantly with the decreasing Cl− concentration. In the soil solution, the corrosive effect of Cl− ions were found to be the least among all three factors, whereas $$HCO_3^-$$ ions had the greatest influence on the corrosion behavior of X70 steel.

The effect of cathodic polarization on the corrosion behavior of X65 steel in seawater containing sulfate‐reducing bacteria

AbstractSulfate‐reducing bacteria (SRB) are one of the main reasons for the accelerated corrosion of steel. Cathodic polarization has been reported as an effective and economic method against marine corrosion, including microbiologically induced corrosion. However, the interaction between cathodic polarization and microbial activity has not been well defined. In this study, a fluorine‐doped tin oxide electrode is used to study the effect of cathodic current on SRB cells. Fluorescence microscopy results clearly show that the attachment degree of SRB is dependent on the electric quantity and current intensity. The large electric quantity and high cathodic current (400 mA/m2 × 30 h) can effectively inhibit bacterial attachment and subsequent biofilm formation. Furthermore, the effect of cathodic potential on the corrosion behavior of X65 steel in the presence of SRB is systematically investigated. Results show that the impressed charges, the increase of pH, and the formation of calcareous deposits on the electrode surface at the cathodic potential of −1,050 mV/SCE inhibit the attachment of SRB. In turn, the presence of SRB also interferes with the electrochemical reactions that occur during the polarization process, thus increasing the cathodic current. The interaction between SRB‐induced corrosion and the process of preventing corrosion by various cathodic potentials is discussed.

Experimental study on the corrosion behavior of X70 steel under asymmetric dynamic DC interference

AbstractThe corrosion behavior of X70 steel in simulated soil environment under asymmetric dynamic direct current (DC) interference was studied by immersion tests. The experimental results showed that the negatively asymmetric dynamic DC interference would induce localized corrosion. Under the same dynamic period of 160 ±80 s, when the negative half‐wave current density remained stable at −10 mA/cm2 and the positive half‐wave one decreased from 7 to 1 mA/cm2, the equivalent diameters of the localized corrosion zones became smaller and the steel samples demonstrated typical pitting corrosion morphologies. To further explore the effect of asymmetric dynamic DC interference on the localized corrosion behavior of carbon steel, a variety of experimental measurements were carried out including real‐time DC potential monitoring, in‐situ near‐surface pH measurements, cyclic voltammetry, and Mott–Schottky tests. It was found that the localized corrosion behavior was probably related to the breakdown of passive film formed on the metal surface exposed to negatively asymmetric DC current generated high pH conditions.

Effect of Applied Potential and Sulfate Reducing Bacteria on Corrosion Behavior of X80 Steel in Dagang Soil Simulated Solution

Effect of Applied Potential and Sulfate Reducing Bacteria on Corrosion Behavior of X80 Steel in Dagang Soil Simulated Solution

Study of Corrosion Behavior of X80 Steel in Clay Soil with Different Water Contents under HVDC Interference

Study of Corrosion Behavior of X80 Steel in Clay Soil with Different Water Contents under HVDC Interference

Corrosion Behavior of X80 Steel Under Anodic Polarization

Corrosion Behavior of X80 Steel Under Anodic Polarization

Study on Corrosion Behavior of X80 Steel in Guangdong Soil with Different Water Contents under HVDC Interference

Study on Corrosion Behavior of X80 Steel in Guangdong Soil with Different Water Contents under HVDC Interference

Influence of Temperature on the Corrosion Behavior of X80 Steel in an Acidic Soil Environment

Influence of Temperature on the Corrosion Behavior of X80 Steel in an Acidic Soil Environment

Corrosion behavior of X80 steel under disbond coating interfered with AC

Purpose This paper aims to research the corrosion behavior of the metal under the disbonded coatings interfered with AC through electrochemical method. Design/methodology/approach The corrosion behavior of the metal under disbond coating interfered with alternate stray current (AC) was studied by electrochemical methods using the rectangular coating disbonded simulator. The obtained data from electrode potential test, electrochemical impedance spectroscopy (EIS) and polarization curves in simulated soil solution indicated that under the natural corrosion condition, the self-corrosion potential and the corrosion current density of the metal at different depths under disbond coating had obviously changed if there was AC interference. Findings The self-corrosion potential of the metal at the same depths under disbond coating shifted negatively with the rising of the AC voltage. Under the condition of cathode polarization, there was still obvious potential gradient with the extension of the deep peeling of the coating gap, and the corrosion current density of the test points was minimum, and the protection effect was best when the cathode protection potential was −1.0 V. When the metal was applied with over-protection, the corrosion rate of the metal increased as AC stray current flowing through it increased. Originality/value This paper used the rectangular aperture device to study the corrosion behavior of X80 steel under the disbonded coatings through electrochemical methods when the AC stray current interference voltage was 0V, 1V, 5V or 10V and the protection potential was 0V, −0.9V, −1.0V, −1.2V or −1.3V, respectively. There is great significance to the safe operation and long-term service of pipeline steel in soil environment.

Fractal characteristics of AC corrosion morphology of X80 pipeline steel in coastal soil solution

Purpose Pipelines are seriously corroded due to the close distance between pipelines and high voltage transmission lines. The purpose of this paper is to study the influence of alternating current (AC) on corrosion behavior of X80 pipeline steel in coastal soil solution. Design/methodology/approach The corrosion behavior of X80 steel under different AC densities in coastal soil solution was investigated by electrochemical measurements and image processing technology. Furthermore, a quantitative description model of AC corrosion through fractal dimension of corrosion image was established. Findings The results show that under low AC density the X80 steel is mainly uniform corrosion, and once AC density reaches 150 A/m2, the corrosion morphology gradually turns to pitting corrosion with irregular circle. For another aspect, the fractal dimension of corrosion images shows that the two/three-dimensional fractal dimension increase with the increase of AC density, presenting a linear and an exponential relationship respectively. In addition, the variation of the three-dimensional fractal dimension is the same as that of average corrosion rate. The threshold of the increasing trend of fractal dimension as well as corrosion type is 150 A/m2. Originality/value The investigation provides a quantitative method to describe AC corrosion morphology through fractal dimension. Furthermore, the method is of benefit to process corrosion images automatically.

The Effect of Annealing Time on Microstructure and AC Corrosion Behavior of X80 Steel in Simulated Solution of Alkaline Soil

The alternating current (AC) corrosion behavior of X80 steels annealed for different times was investigated in an alkaline soil simulation solution by electrochemical measurement, immersion test and surface analysis technology. The results show that with or without AC interference, the steels annealed for various times have different corrosion resistance. The anticorrosion resistance of steel improves with an increase in annealing time. AC interference results in the evolution of the main cathodic reaction, and facilitates the corrosion of the steels. The steel annealed for 20 min presents a more severe corrosion degree with distinct pits. The corrosion behavior of the steels annealed for different times with AC application is closely related to the microstructure. A decrease in pearlite reduces the number of galvanic corrosion cells, decreasing the corrosion rate of steel. And the grain increase is beneficial for improving the corrosion resistance of the annealed steel.

Corrosion behavior of X65 steel in CO2-saturated oil/water environment of gathering and transportation pipeline

Purpose The purpose of this paper is to investigate the corrosion behavior of X65 steel in the CO2-saturated oil/water environment using mass loss method, potentiodynamic polarization technique and characterization of the corroded surface techniques. Design/methodology/approach The weight loss analysis, electrochemical study and surface investigation were carried out on X65 steel that had been immersed in the CO2/oil/water corrosive medium to understand the corrosion behavior of gathering and transportation pipeline steel. The weight loss tests were carried out in a 3 L autoclave, and effects of water cut and temperature on the CO2 corrosion rate of X65 steel were studied. Electrochemical studies were carried out in a three-electrode electrochemical cell with the test temperature was 60°C, and the CO2 partial pressure was 1 atm by recording open circuit potential/time and potentiodynamic polarization characteristics. The surface and cross-sectional morphologies of corrosion product scales were characterized using scanning electron microscopy. The phases of corrosion product scales were investigated using x-ray diffraction. Findings The results showed that due to the wetting and adsorption of crude oil, the corrosion morphology of X65 steel changed under different water cuts. When the water cut of crude oil was 40-50 per cent, uniform corrosion occurred on the steel surface, accompanied by local pitting. While the water cut was 70-80 per cent, the resulting corrosion product scales were thick, loose and partial shedding caused platform corrosion. When the water cut was 90 per cent, the damaged area of platform corrosion was enlarged. Crude oil can hinder the corrosion scales from being dissolved by the corrosive medium, and change dimension and accumulation pattern of the crystal grain, thickness and structure of the corrosion scales. Under the corrosion inhibition effect of crude oil, the temperature sensitive point of X65 steel corrosion process moved to low temperature, appeared at about 50°C, lower corrosion rate interval was broadened and the corrosion resistance of X65 steel was enhanced. Originality/value The results can be helpful in selecting the applicable corrosion inhibitors and targeted anti-corrosion measures for CO2-saturated oil/water corrosive environment.

Effect of dynamic DC stray current on corrosion behavior of X70 steel

AbstractCorrosion behavior of X70 steel under the application of dynamic DC stray current was investigated in simulated soil solution by immersion tests and electrochemical measurements. Experimental results indicated that the corrosion rate of X70 steel under dynamic DC stray current was strongly influenced by the dynamic period. When the dynamic period was <80 s, the corrosion rate was only approximately 1–7% of that caused by an equivalent amount of steady direct current. However, as the dynamic period became >80 s, the corrosion rate increased significantly with the dynamic period. And finally when the dynamic period was >1 hr, the corrosion rate was nearly equal to 100% of that caused by an equivalent amount of steady direct current. Meanwhile, the surface examination showed that the specimens experienced uniform corrosion under the experimental conditions. On the basis of the experiment results, the dynamic DC stray current corrosion mechanism of X70 steel under the experimental conditions was discussed, which was closely related to the electric double‐layer structure at the electrode/solution interface and dynamic electrochemical reactions under dynamic stray current.

Mechanism of microbiologically influenced corrosion of X65 steel in seawater containing sulfate-reducing bacteria and iron-oxidizing bacteria

Sulfate-reducing bacteria (SRB) and iron-oxidizing bacteria (IOB) are one of the typical representatives of anaerobic and aerobic bacteria, which can form a synergistic community (mixed species biofilm) on the surface of material. In this work, the corrosion behavior of X65 steel in seawater containing SRB and IOB was investigated with electrochemical impedance spectroscopy, potentiodynamic polarization, scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Results showed that the combination of anaerobic SRB and aerobic IOB affected the corrosion behavior of X65 steel greatly, and the corrosion rate was higher than that in single SRB or IOB medium. The corrosion mechanisms of X65 steel in mixed SRB and IOB could be divided into three stages, which were controlled by the metabolic activities of bacteria (SRB and IOB), biofilm structure and metabolic products comprehensively.

Synergistic effect of O2 and SO2 gas impurities on X70 steel corrosion in water-saturated supercritical CO2

The synergistic effect of O2 and SO2 on the corrosion behavior of X70 steel was evaluated in water-saturated supercritical CO2 using weight loss analysis and surface analysis techniques. Corrosion experiments were conducted at 40°C and 100bar to simulate typical CO2 transportation conditions. Results indicate that the synergistic effects of O2 and SO2 enhance or inhibit the corrosion rate, depending on the concentration variation of impurities. SO2 had the highest corroding influence on X70 steel, with the corrosion rate of 1.10 mm/year with the addition of 500 ppmv SO2. The presence of SO2 changed the corrosion mechanism and the final products of corrosion consisted mostly of FeSO3. Low concentrations of O2 increased the corrosion rate (0.09 mm/year) primarily by destroying the integrity of the FeCO3 product film in the absence of SO2. However, the corrosion rate of X70 steel progressively decreased to 0.03 mm/year as the concentration of O2 increased to 1000 ppmv, due to high concentration of O2 causing the steel substrate to enter the passivation zone. This study is important for a number of industrial applications, as it provides a theoretical basis for corrosion control of supercritical CO2 pipelines.

Study on the Influence of AC Stray Current on X80 Steel under Stripped Coating by Electrochemical Method

The effect of AC stray current density on corrosion behavior of X80 steel with stripped coating defects was studied by electrochemical method. The experimental results showed that the open circuit potential of X80 steel was shifted negatively due to the existence of AC interference. The degree of negative shift increased with the increasing of AC stray current density. And the potential after the cut of AC interference was still more negative than before. That is, the corrosion interference continued after cutting the AC power. In the initial stage of the experiment, the corrosion current density with 30A/m2 AC stray current interference was about 1.4 times of that without AC interference, while the corrosion current density with 50A/m2 AC stray current interference was about two times of that without AC interference.