Corrosion Behavior Of X80 Steel Research Articles

The corrosion behavior of X65 steel in CO2/oil/water environment of gathering pipeline

Purpose The purpose of this paper was to investigate the corrosion behavior of X65 steel in the CO2/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 pipeline steel. The weight loss tests were carried out in a 3L autoclave, and effects of flow velocity, CO2 partial pressure and water cut 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 of 60°C and CO2 partial pressure of 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 corrosion rates of X65 steel both increased at first and then decreased with the increase of flow velocity and CO2 partial pressure, and there were critical velocity and critical pressure in the simulated corrosive environment, below the critical value, the corrosion products formed on the steel surface were loose, porous and unstable, higher than the critical value, the corrosion product ?lms were dense, strong adhesion, and had a certain protective effect. Meanwhile, when the flow velocity exceeded the critical value, oil film could be adsorbed on the steel surface more evenly, corrosion reaction active points were reduced and the steel matrix was protected from being corroded and crude oil played a role of inhibitor, thus it influenced the corrosion rate. Above the critical CO2 partial pressure, the solubility of CO2 in crude oil increased, the viscosity of crude oil decreased and its fluidity became better, so that the probability of oil film adsorption increased, these factors led to the corrosion inhibition of X65 steel reinforced. The corrosion characteristics of gathering pipeline steel in the corrosive environment containing CO2 would change due to the presence of crude oil. Originality/value The results can be helpful in selecting the suitable corrosion inhibitors and targeted anti-corrosion measures for CO2/oil/water corrosive environment.

Effect of Temperature on Corrosion Behavior of X65 Steel in Simulated Deep Sea Environment

Effect of Temperature on Corrosion Behavior of X65 Steel in Simulated Deep Sea Environment

Effect of Deep Sea Pressures on the Corrosion Behavior of X65 Steel in the Artificial Seawater

The corrosion behaviors of X65 steel in the artificial seawater at different hydrostatic pressures are investigated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy measurements and weight loss measurements. The corroded morphologies and the corrosion products are also investigated by scanning electron microscopy, X-ray diffraction analysis and Raman analysis. The results show that the corrosion current increases as the hydrostatic pressure increases. The charge transfer resistance decreases as the hydrostatic pressure increases. The corrosion products are mainly composed of γ-FeOOH and Fe3O4 at the atmospheric pressure, while the main components are γ-FeOOH, Fe3O4, and γ-Fe2O3 at the high pressure. The hydrostatic pressure accelerates the corrosion of X65 steel due to its effect on the chemical and physical properties of corrosion products, including the promoted reduction of γ-FeOOH and the wider and deeper cracks on the corrosion products layer.

Corrosion Behavior of X80 Pipe Steel under HVDC Interference in Sandy Soil

With the development of high voltage direct current (HVDC) systems, some pipelines have been badly interfered. The corrosion mechanism of pipelines has not been clearly clarified. In this work, laboratory experiments were designed to study the corrosion behavior of X80 steel under HVDC interference in sandy soil. The corrosion rates were related to the change in direct current (DC) density, which experienced three stages in the interference process. As soon as high DC interference voltage was applied to the working electrode, the current density increased sharply to a peak value in a few seconds. It then decreased rapidly to a steady value over dozens of seconds. Finally, it remained steady for the remaining time. With the measurement of local soil properties, the change in DC density was attributed to the local soil temperature increment, the water content decrement, and the substantial growth in the soil spread resistance. Moreover, the parameters contribute to the corrosion reaction during the interference process. The corrosion products were characterized at different times of interference via Raman spectroscopy. Lepidocrocite was produced under high DC density and then transformed to hematite under low DC density. Based on the above, the corrosion model during HVDC interference is proposed.

Influence of Soil Water Content Adjusted by Simulated Acid Rain on Corrosion Behavior of X80 Steel in Red Soil

Influence of Soil Water Content Adjusted by Simulated Acid Rain on Corrosion Behavior of X80 Steel in Red Soil

Corrosion behavior of X65 steel in seawater containing sulfate reducing bacteria under aerobic conditions

The corrosion behavior of X65 steel was investigated in the seawater inoculated with sulfate reducing bacteria (SRB) under the aerobic environment by electrochemical impedance techniques and immersion tests. The corroded morphologies and the composition of the corrosion products were investigated. The variation of the solution parameters including the bacterium number, the pH value and the soluble iron concentration were also investigated. The results indicated that in the SRB-containing system, the impedance responses presented a depressed semi-circle in the initial period, which then turned into the blocked electrode characteristic during the later immersion. The biofilm, mainly composed of extracellular polymeric substances, Fe(OH)3, γ-FeOOH and α-Fe2O3, formed and degraded with the SRB growth. The soluble iron concentration initially increased, then rapidly decreased and later slowly increased. In the SRB-containing seawater under the aerobic environment, the X65 steel was corroded in the initial immersion. The corrosion became inhibited with the forming of the biofilm during the subsequent immersion. The inhibition efficiency rapidly increased in the logarithmic phase, remained stable in the stationary phase and then decreased in the declination phase. In the corrosion process, the biofilm metabolized by SRB played a key role in the corrosion inhibition of X65 steel.

Effect of soil moisture content on corrosion behavior of X70 steel

Effect of soil moisture content on corrosion behavior of X70 steel

Effects of O2 and SO2 on Water Chemistry Characteristics and Corrosion Behavior of X70 Pipeline Steel in Supercritical CO2 Transport System

The water chemistry characteristics of supercritical CO2 streams and the corrosion behavior of X70 steel in a supercritical CO2 system containing O2 and/or SO2 impurities were investigated by therm...

Study on the influence of environmental factors on AC corrosion behavior and its mechanism

The AC corrosion behavior of X70 steel under the combined action of cathodic protection and AC interference was studied by the laboratory simulation experiments in two kinds of typical soil simulated environments with different contents of calcium ion (Ca2+), magnesium ion (Mg2+), and sodium ion (Na+). The mechanisms of AC corrosion in different environments were investigated by process parameter monitoring, electrochemical measurement, corrosion morphology, and product analyses. The results showed that the corrosion rate of X70 steel in the simulated environment with higher Na+ content was 2 times higher than that in the simulated environment with higher Ca2+ and Mg2+ content under the same CP potential and AC current density. The reason was analyzed and it was found that the performance of product film, AC current distribution through the double layer interface of steel/electrolyte, and the enrichment of some ions near the interface attributed to AC corrosion rate in different environments.

Effect of impurity interaction on the corrosion film characteristics and corrosion morphology evolution of X65 steel in water-saturated supercritical CO2 system

The corrosion behavior of X65 steel in water-saturated supercritical CO2 system containing NO2 with or without O2, H2S and SO2 impurities was investigated using weight loss measurement and surface analysis techniques. The interactions between NO2 and O2, SO2 or H2S promoted the formation of extra corrosive species and subsequently changed the corrosion film characteristics. In water-saturated supercritical CO2-NO2-O2-SO2-H2S system, FeSO4 and S preferentially formed in the early corrosion stage due to the impurity interactions. As the corrosion time prolonged, (NH4)Fe3(SO4)2(OH)6 and FeOOH formed due to the subsequent reactions of the impurity interaction products, and S disappeared in the corrosion scale via participating in the subsequent corrosion reactions during long-term corrosion. Localized corrosion was initiated by the inhomogeneous precipitation of acid-rich water in the presence of NO2. However, the propagation rate of the corrosion pit in depth direction greatly reduced with time, and the corrosion morphology of X65 steel shifted from localized corrosion towards general corrosion during long-term corrosion.

Corrosion Behavior of X80 Steel with Coupled Coating Defects under Alternating Current Interference in Alkaline Environment

The corrosion behavior of X80 steel in the presence of coupled coating defects was simulated and studied under the interference of alternating current (AC) in an alkaline environment. The results from electrochemical measurements showed that the electrode potential of the coating defect with the smaller exposed area was lower than that with the larger area, which indicated that the steel with the smaller coating defect was more prone to corrosion. The result of weight loss tests also showed that the smaller coating defect had induced a higher corrosion rate. However, the corrosion rate of X80 steel at the larger coating defect decreased gradually with the increase of the larger defect area at a constant smaller defect area. The corrosion morphology images showed that the coating defects with smaller areas suffered from more severe pitting corrosion.

Effect of exposure angle on the corrosion behavior of X70 steel under supercritical CO2 and gaseous CO2 environments

The corrosion behavior of X70 steel with different exposure angles under supercritical CO2 and gaseous CO2 environments were studied. The results showed that the diffusion of the corrosive species in the water droplets in supercritical CO2 phase was more significant than that in aqueous phase, which accelerated the cathodic reactions. The corrosion rate in supercritical CO2 phase was much higher than that in gaseous CO2 phase due to the higher mutual solubility (g/L) of H2O and CO2 in supercritical CO2 phase. Exposure angle significantly affected the corrosion behavior of the steel in supercritical CO2 phase.

Electrochemical Corrosion Behavior of X70 Steel in Sand Soil Contaminated by Copper(II)

Electrochemical Corrosion Behavior of X70 Steel in Sand Soil Contaminated by Copper(II)

Influence of Acetic Acid on Top Localized Corrosion of X70 Steel Pipeline in CO2 Containing Wet Gas

The electrochemical corrosion behavior of X70 steel in CO2 saturated solution with vari- ous concentrations of acetic acid was studied by means of potentiodynamic polarization measure- ment and EIS. Whilst the influence of acetic acid on the top localized corrosion (TLC) of X70 steel pipelines was examined in a set of high temperature and high pressure autoclave. The results showed that in the CO2 saturated solution, the X70 steel was inactive state. While the free corrosion potential of X70 steel shifted positively and its corrosion current density increased with the increas- ing concentration of acetic acid, which may be related to the rising H + concentration, so that the ca- thodic reaction was promoted. In addition, because of the presence of acetic acid, the corrosion scale become loose and easy to detach from the substrate. Finally a pitting corrosion model was proposed to describe the initiation and evolution of the pitting process.

Effect of impurity on the corrosion behavior of X65 steel in water-saturated supercritical CO2 system

A range of impurities from various CO2 capture processes may exist in supercritical CO2 transport pipeline in carbon capture and storage process. In this regard, the corrosion behavior of X65 steel in water-saturated supercritical CO2 containing O2, H2S, SO2 or NO2 impurity was investigated using weight loss measurement and surface characterization. The corrosion impact factor was defined which showed that NO2 or SO2 had the greatest influence on the corrosion of X65 steel, followed by H2S and O2. Localized corrosion occurred in water-saturated supercritical CO2 system containing NO2 with or without other impurities. Low concentrations of impurities could notably change the corrosion rate and the characteristics of corrosion scale via changing the corrosion mechanism, and thus the corrosion effect of CO2 weakened in water-saturated supercritical CO2 system containing impurities.

Corrosion behavior of X70 steel in sands at different charging times

AbstractTo investigate the corrosion behavior and mechanisms of X70 steel in sands, polarization curves (PCs) and electrochemical impedance spectroscopy (EIS) were carried out using an electrochemical test set-up. X70 steel represents a common and standard API designation for pipelines with 70 ksi or 485 MPa strength. For acceleration of the process at different charging times, a direct current (DC) with 6 V voltage was applied. The results show that DC accelerates the corrosion process of X70 steel in sands and that the corrosion rate increases with charging time of the DC. Corrosion potential changes the process of positive-negative-positive charging with increasing process time, indicating that pore water, oxygen substances and corrosion ions of sands all affect the corrosion reaction. Based on the experimental results from the equivalent circuit of EIS, the corrosion process can be divided into the following three phases: developing and formatting of corrosion product film, pitting corrosion, and progressing pitting period. The low-frequency inductive slope on the EIS graph appears during the period of corrosion pitting as resulting from the corrosion product film. The film slows down the corrosion process and reduces the corrosion rate temporarily. With the increasing charging time, the corrosion product film may be damaged and the corrosion rate will thus increase significantly. The testing results of energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM) indicate iron hydroxides as the original corrosion products. With increasing charging time, the original corrosion products may be oxidized to form stable and protective film products such as Fe2O3 and Fe3O4. Lastly, during the pitting progressing period, oxidized film products will be damaged and the corrosion rate increases with increasing charging time.

Synergistic effect of O2, H2S and SO2 impurities on the corrosion behavior of X65 steel in water-saturated supercritical CO2 system

The synergistic effect of O2, H2S and SO2 impurities on the corrosion behavior of X65 steel corrosion was evaluated in the water-saturated supercritical CO2 system. Weight loss measurements showed that the synergistic effect of multiple impurities significantly increased the corrosion rate of steel. Surface characterization of corrosion scales using SEM, EDS and XRD showed that low concentrations of impurities notably changed the characteristics of corrosion scales. The interactions among O2, H2S and SO2 resulted in additional formation reactions of elemental sulfur, sulfuric acid and water and consequently accelerated the corrosion of steel consistent with the high synergistic interaction impact factors.

Effect of O2 and H2S impurities on the corrosion behavior of X65 steel in water-saturated supercritical CO2 system

The corrosion behavior of X65 steel in water-saturated supercritical CO2 containing O2 and/or H2S impurities was investigated by means of weight loss measurements and surface characterization. The results showed that the addition of O2 or H2S impurities increased the corrosion rate of X65 steel in water-saturated supercritical CO2 system. The effect of H2S on the corrosion of X65 steel was greater than that of O2. The corrosion was more severe with the coexistence of O2 and H2S. The change in corrosion behavior was attributed to the fact that low concentrations of O2 and/or H2S can notably change the corrosion mechanism.

The effect of hydrogen on stress corrosion behavior of X65 steel welded joint in simulated deep sea environment

In order to investigate stress corrosion cracking (SCC) of X65 pipeline steel and its welded joint area in deep sea environment. The simulated methods were used to obtain the welded joint of hardening and softening tissue in heat affected zone (HAZ) by annealing at 1300°C for 10min and then, normalized in air and quenched in water respectively; the other was to get 1000m depths of marine environment. The effect of hydrogen on SCC behavior of X65 pipeline steel in simulated deep sea environment was analyzed by a combination of hydrogen-charging, slow stain rate test (SSRT), scanning electron microscope (SEM) and electrochemistry. Results demonstrated that with the increasing of charging current density, Fracture of as-received appeared brittle characteristics and normalized and quenched steel generated micro cracks, Hydrogen-charging will enhance the SCC susceptibility of the steel in simulated deep sea environment. The corrosion potential of X65 steels was low in deep sea environment with hydrogen evolution reaction and showed some SCC sensitivity in deep sea environment. Heat treatment altered the microstructure of the steel, resulting in a change of SCC susceptibility. In particular, the quenched steel with a bainite micro-structure which had a higher SCC susceptibility than as-received and normalized steel in deep sea environment.

Short-term electrochemical corrosion behavior of pipeline steel in saline sandy environments

In this study, we investigate the short-term electrochemical corrosion behavior of X70 pipeline steel in salinized sandy soil using the electrochemical impedance spectroscopy (EIS). The results show that the corrosion behavior of X70 steel in sandy soils with a relatively high water content (~18%) is mainly dominated by pitting or localized corrosion, which is controlled by charge-transfer processes. The reason can be attributed to the loose corrosion products (unable to produce an effective protective layer) and discontinuous gradation in sand particles. EIS plots of X70 steel consist of two capacitive loops at the initial stage of corrosion, while a capacitive arc at high-, medium-, and low-frequency is developed after 12h of corrosion. The capacitive loop formed at the high frequency indicates the resistance and capacitance generated by the penetration of ions into the metal surface through the sand pores and the defects of the corrosion product film.