Corrosion Behavior Of Pipeline Steel Research Articles

Corrosion Behavior of X80 Steel in a Simulated Soil Solution Under Square-Wave Current Interference

The buried pipeline is disturbed by the dynamic direct current (DC) stray current with the subway as the main leakage source, which has the safety risk of accelerating corrosion, resulting in pipeline failure, which not only causes economic losses but also threatens personal safety. Therefore, it is necessary to study the corrosion behavior of pipeline steel under dynamic DC interference. The corrosion behavior of X80 steel under dynamic DC interference were studied by a mass loss test, alternating current impedance, circuit simulation, x-ray diffraction, and a Pourbaix diagram. Combined with the corrosion efficiency and Pourbaix diagram of the Fe-H2O system, the reversible process and reduction process mechanism in the Faraday process are proposed. The reason why the corrosion efficiency slows down in the process of non-Faraday is analyzed by the electric double-layer model of equivalent circuit calculation. In addition, based on the above corrosion process, the corresponding conceptual model of the corrosion mechanism is proposed. The experimental results show that with the asymmetry of positive and negative half-cycle interference duration and the increase of current density, the corrosion efficiency, and current corrosion efficiency of X80 steel decrease, and local corrosion intensifies. The length of the negative half-cycle interference affects the capacitive charge-discharge effect at the metal/solution interface and the reduction reaction process of corrosion products, resulting in corrosion slowing down and corrosion efficiency reduction. This is also an important reason for the reduction of corrosion mass loss observed in the experiment compared with steady-state DC.

Local corrosion behavior of pipeline steel under deposition layer in produced water of Alkali/ Surfactants/ Polymers

The metal pipelines in ASP(Alkali/ Surfactants/ Polymers) flooding systems will suffer from severe under deposit corrosion. In this work, the corrosion behavior of AISI 1020 carbon steel under the deposition of SiO2 or CaCO3 was investigated in produced fluids of ASP (Alkali/ Surfactants/ Polymers) flooding. The results showed that the deposition layer inhibited the uniform corrosion of the metal and promoted the localized corrosion of the metal, and the promotion effect of the calcium carbonate deposition layer was stronger than that of the silica deposition layer. The metal corrosion product under the SiO2 deposition layer was Fe3O4 and FeOOH, and the metal corrosion product under the CaCO3 deposition layer was Fe3O4 and Fe2O3. The type and extent of localized corrosion have varied due to differences in deposited layers and corrosion products. The occurrence and development of localized corrosion of metals under deposition can be monitored by WBE. Based on the above conclusions, appropriate corrosion mitigation strategies are proposed to prevent future failures.

Mechano-electrochemical interaction of high-strength pipeline steels with Al-Ti deoxidization and Mg-Ca compound treatment

The micro-zone interface of inclusions with the steel matrix of X70 high-strength pipeline steel with Al-Ti deoxidization and Mg-Ca compound treatment in the tropical marine environment was investigated. Results revealed that the Volta potential difference increased in proportion to the residual stress at the interface of inclusions with the steel matrix. The early corrosion behavior of pipeline steel was investigated by immersion testing and corrosion morphology assessment. Three stages of the early corrosion process of pipeline steel were elucidated based on micro mechano-electrochemical (M-E) interaction. Thermodynamic and kinetic models of M-E interactions at the micro-scale were proposed.

Effects of load waveforms on stress corrosion behavior of pipeline steel

The effects of different load waveforms on stress corrosion cracking (SCC) of X70 pipeline steel were studied by means of fluctuating slow strain rate tensile test (F-SSRT). The results show that the SCC sensitivity of F-SSRT specimens with square wave loading is weak, and the fracture is straight; the SCC sensitivity of F-SSRT specimens with superimposed triangular wave loading is in the middle, and the fracture edge is serrated; The F-SSRT specimens with superimposed sine wave loading own the strongest SCC sensitivity, and the fracture is an oblique section fracture extending along the 45° direction. Different superimposed loads with different waveforms result in different SCC test results including different fracture morphology and change rules, which are caused by the change of the direction and magnitude of the applied force of the superimposed load, not only attributing to the different superimposed load energy.

Effect of Flow on the Corrosion Behavior of Pipeline Steel in Supercritical CO2 Environments with Impurities

Corrosion is a major concern in transmission pipelines that transport captured CO2. While dry CO2 is noncorrosive, significant corrosion has been reported in dense-phase CO2 with trace amounts of water and impurities such as O2, H2S, SOx, and NOx. The aim of this work is to improve our understanding of the physicochemical aspects of the corrosion of carbon steels in the high-pressure environments associated with CO2 transmission pipelines. The effect of flow on the corrosion of X65 carbon steel was investigated in a series of autoclave tests with different combinations of impurity concentrations in supercritical CO2 conditions (8 MPa and 35°C). The corrosion rate of specimens was determined by weight loss measurements. The surface morphology and composition of the corrosion product layers were characterized using surface analytical techniques (scanning electron microscopy, eneregy dispersive x-ray spectroscopy, and Raman microscopy). Localized corrosion was measured via surface profilometry after corrosion products were removed. Results showed that no corrosion was observed in the supercritical CO2 with 650 ppmv of water, 50 ppmv SO2, and 100 ppmv NO, but corrosion occurred when SO2 concentration was increased to 4,500 ppmv and 40,000 ppmv of O2 was added to the system. The presence of flow significantly accelerated the corrosion of carbon steel. Furthermore, localized corrosion was observed in the presence of both O2 and flow.

Research on Dynamic Alternating Current Corrosion Behavior of X65 Pipeline Steel Under Cathodic Protection

An indoor corrosion simulation experiment device was built to explore the influence of dynamic alternating current (AC) interference on the corrosion behavior of pipeline steel under different cathodic protection (CP) levels. When the interference time in each interference cycle is 350 s, the dynamic AC corrosion rate was comparable to the steady AC corrosion rate. For JAC of 30 A/m2, the corrosion rate of the specimen can be controlled below 0.0254 mm/y when the CP current density is higher than 0.06 A/m2. As JAC is greater than or equal to 100 A/m2, with the increase of the CP current density, the corrosion rate of the specimens decreased first, then increased and decreased again. In this paper, the real-time AC/DC potential on the surface of the specimen is monitored, combined with the Pourbaix diagram and the evolution of corrosion product film. The dynamic AC corrosion mechanism under different CP levels was explored.

Corrosion Behavior of Pipeline Steel in Oilfield Produced Water under Dynamic Corrosion System

Corrosion Behavior of Pipeline Steel in Oilfield Produced Water under Dynamic Corrosion System

Effect of electric-arc-induced ablation on corrosion behavior of pipeline steel under high-voltage direct current interference

PurposeThe purpose of this study is to elucidate the effects of electric-arc-induced ablation on the corrosion behavior of pipeline steel in neutral and high pH environments.Design/methodology/approachElectrochemical testing, an atmospheric-pressure immersion experiment and various techniques (e.g. scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy) were used to examine the effects of electric-arc-induced ablation on the corrosion behavior of pipeline steel in neutral and high pH environment.FindingsElectric-arc-induced ablation occurred preferentially in areas of inclusion. The corrosion resistance of an ablation pit was lower than that of non-ablation areas. In the neutral soil solution, general corrosion was the dominant corrosion that affected pipeline steel; the effect of ablation was small but pitting corrosion could still be induced. In a high pH environment, the samples without ablation were passivated, whereas the samples with ablation pits could not be passivated; the ablation pits were likely to develop pitting corrosion.Originality/valueElectric-arc-induced ablation can reduce the corrosion resistance of pipeline steel under high-voltage direct current interference.

Influence of fuel combustion on the corrosion behavior of pipeline steels in fire flooding technology

To study the oxidation behavior of a commonly used pipeline materials of 37Mn5 steel in the process of fire flooding technology, a simulation device of organic fuel combustion was designed and used for comparative study between air and kerosene atmosphere. The products generated after kerosene combustion greatly affected the growth of iron oxides at 600 and 700 °C. In air, the oxide scale shows a defective morphology with bulge and spallation. While in the kerosene atmosphere, carbon particles after incomplete combustion can exist on the surface and inside the oxide scale, which would inhibit the reduction of oxides by carbon in substrate and the decarburization of 37Mn5 steel.

Evaluation of the Influence of the Combination of pH, Chloride, and Sulfate on the Corrosion Behavior of Pipeline Steel in Soil Using Response Surface Methodology.

External damage to buried pipelines is mainly caused by corrosive components in soil solution. The reality that numerous agents are present in the corrosive environment simultaneously makes it troublesome to study. To solve that issue, this study aims to determine the influence of the combination of pH, chloride, and sulfate by using a statistical method according to the design of experiment (DOE). Response surface methodology (RSM) using the Box–Behnken design (BBD) was selected and applied to the design matrix for those three factors. The input corrosion current density was evaluated by electrochemical tests under variable conditions given in the design matrix. The output of this method is an equation that calculates the corrosion current density as a function of pH, chloride, and sulfate concentration. The level of influence of each factor on the corrosion current density was investigated and response surface plots, contour plots of each factor were created in this study.

Corrosion Behavior of Pipeline Steel Under High-speed Railway Dynamic AC Interference

Corrosion Behavior of Pipeline Steel Under High-speed Railway Dynamic AC Interference

The effect of nitrate reducing bacteria on the corrosion behavior of X80 pipeline steel in the soil extract solution of Shenyang

The effect of NRB on the corrosion behavior of X80 pipeline steel in the soil extract solution of Shenyang was studied using polarization curve, electrochemical impedance spectroscopy, weight-loss tests and scanning electron microscope. The results show that NRB accelerates the corrosion rate of steel and promotes the formation of pitting holes on the surface of steel. XPS results show that the types of corrosion products are unchanged. Moreover, electrochemical measurements can effectively evaluate the corrosion behavior of pipeline steel affected by NRB in real time. The data in this work support that NRB can be responsible for pipeline perforation and leakage.

Study of Electrochemical Behavior, Hydrogen Permeation and Diffusion in Pipeline Steel

The pipeline steels which are used for transportation of natural gas and crude oil suffer from hydrogen damage at their internal as well as external surfaces. The internal surfaces of pipelines are generally affected due to hydrogen induced cracking and the external surfaces due to the soil environmental conditions which cause stress corrosion cracking. In the present investigation, the electrochemical corrosion behavior of X70 pipeline steel was studied in sour environment and near neutral soil environment. To assess the mechanism of hydrogen damage in steel, electrochemical hydrogen charging and permeation techniques were used to characterize the hydrogen distribution, trapping and its diffusion in X70 pipeline steel. It has been found that corrosion behavior of pipeline steel in the sour environment is higher than the near neutral soil solution. From the hydrogen permeation study it is established that the hydrogen permeation rate increases with the square root of the charging current density, and the increase of hydrogen flux is directly proportional to the subsurface hydrogen concentration.

Effect of Alternating Current on Passive Film and Corrosion Behavior of Pipeline Steel with Different Microstructures in Carbonate/Bicarbonate Solution

The relationship between microstructure and alternating current (AC) corrosion behavior of X80 pipeline steel was systematically studied in CO32−/HCO3− solution using corrosion tests and surface analysis technology. The results show that AC prevents the formation of passive film and decreases its stability. AC generates a different damage effect to the passive film on steels with various microstructures. The passive film of normalized microstructure steel has a relatively high stability, followed by the hot-rolled steel, and that of the annealed sample is the most unstable. The influence of AC on passive film of steels with various microstructures causes a difference in the corrosion resistance. The corrosion form of steels with different microstructures applied with AC displays the obvious characteristic of localized corrosion. The normalized microstructure has the optimum corrosion resistance, followed by the hot-rolled steel, and the annealed steel possesses the worst corrosion resistance. The difference in the AC corrosion behavior of X80 steels may be related to the microstructure.

Corrosion behavior of X65 pipeline steel in coastal areas

Purpose To study the corrosion behavior of pipeline steel in coastal areas, a tidal seawater macro-cell corrosion device was built using a cycle soaking tank and a macro-cell corrosion facility to simulate the corrosion behavior of pipeline steel in a simulated coastal environment (dry and wet alternations during seawater-soil corrosion macro-cell processes). Design/methodology/approach The corrosion behaviors were studied via the weight loss method, electrochemical methods and morphological observations on corrosion. Findings The results show that during the initial stage of tidal seawater/soil macro-cell corrosion process of the X65 steel, the working electrode on the seawater side is the anode of the macro-battery. As corrosion progresses, the anode and the cathode of the macro-battery become inverted. As the area ratio and the dry – wet ratio increase, the time of anode and cathode inversion shortens. Galvanic current density decreases as the dry – wet ratio increases and increases as the area ratio increases. The corrosion process of macro-cell is affected by the reversal of anode and cathode. After the reversal of anode and cathode, the corrosion rate is mainly controlled by dry – wet alternating corrosion. Originality/value The corrosion behavior of a pipeline steel in a coastal environment was studied using a tidal seawater macro-cell corrosion device. The synergism effect between the tidal seawater and seawater-soil macro-cell on corrosion behavior was clarified.

Corrosion Behavior of Pipeline Steel with Different Microstructures Under AC Interference in Acid Soil Simulation Solution

Corrosion behavior of X65 pipeline steels with different microstructures under alternating current (AC) interference was investigated in acid soil simulation solution by potentiodynamic polarization curve, potentiostatic polarization curve and immersion test. The results show that superimposed AC causes a sharp increase in corrosion current density of X65 steel. With the increase in iAC, the corrosion current densities of steels with various microstructures increase, especially at high iAC. Hot-rolled steel mainly experiences uniform corrosion, with very slight pit corrosion. Serious corrosion degrees with intensive corrosion pits can be observed on the surfaces of normalized and quenched microstructure steels. The annealed steel exhibits the feature of non-uniform corrosion with some pitting. The steels with various microstructures applied with AC have different corrosion resistance. The normalized steel shows the worst corrosion resistance, then the quenched microstructure, and the hot-rolled steel displays the optimum corrosion resistance. The difference in the microstructure can result in difference in corrosion degree and occurrence position of pitting corrosion of X65 steel. The normalized microstructure composed of polygonal ferrite and a large amount of pearlite and bainite is the most susceptible to AC corrosion.

Corrosion Behavior of Pipeline Carbon Steel under Different Iron Oxide Deposits in the District Heating System

The corrosion behavior of pipeline steel covered by iron oxides (α-FeOOH; Fe3O4 and Fe2O3) was investigated in simulated district heating water. In potentiodynamic polarization tests; the corrosion rate of pipeline steel is increased under the iron oxide but the increaseing rate is different due to the differnet chemical reactions of the covered iron oxides. Pitting corrosion was only observed on the α-FeOOH-covered specimen; which is caused by the crevice corrosion under the α-FeOOH. From Mott-Schottky and X-ray diffraction results; the surface reaction and oxide layer were dependent on the kind of iron oxides. The iron oxides deposit increases the failure risk of the pipeline and localized corrosion can be occurred under the α-FeOOH-covered region of the pipeline. Thus, prevention methods for the iron oxide deposit in the district pipeline system such as filtering or periodic chemical cleaning are needed.

The influence of particle size on the long‐term electrochemical corrosion behavior of pipeline steel in a corrosive soil environment

In this work, the effect of particle size (0.25, 1.0, 1.5 mm) on the electrochemical corrosion behavior of X70 pipeline steel in a 1.5 wt% NaCl sandy soil corrosion system was investigated by electrochemical techniques including linear polarization resistance, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) in combination with SEM‐EDS surface analysis, and X‐ray diffraction characterization. The laboratory experiments indicated that the corrosion rate of X70 pipeline steel increased with decreasing soil particle size to less than 1.0 mm and was mainly determined by a cathodic reaction. Whereas when the soil particle size increased beyond 1.0 mm, the corrosion rate of X70 steel decreased as the soil particle size decreased and the dominant reaction was metal dissolution in the bulk zone, and the corrosion rate was determined by anodic reaction. Additionally, the results of analysis of the metal surface morphologies agreed with the electrochemical measurements results. Corrosion of X70 pipe steel is affected by particle‐sizes in a corrosive soil environment.

Effect of the Size of Soil Particles on the Electrochemical Corrosion Behavior of Pipeline Steel in Saline Solutions

By using a standard quartz replace of sandy soil particles, we investigate the effect of size of soil particles (0.1–0.25 mm, 0.6–1.0 mm) on the electrochemical corrosion behavior of X70 pipeline steel in sandy-soil corrosive environment simulated by 3.5 wt.% sodium chloride (NaCl) with the help of the polarization curve and electrochemical impedance spectroscopy (EIS) technology. The results indicate that the polarization resistance of X70 steel decreases as the particle size decreases. For all polarization curves, a right shift of the cathodic branch with decreasing particle sizes is observed. The corrosion of X70 steel is controlled by the cathode process of diffusion and oxygen reduction at the metalenvironment interface, the intensity of which increases as the particle size decreases.

Effect of H2S on the Corrosion Behavior of Pipeline Steels in Supercritical and Liquid CO2 Environments

The objective of the present study is to evaluate the corrosion properties of pipeline steels in CO2/H2S/H2O mixtures with different amounts of water (undersaturated and saturated) related to a natural gas transportation pipeline. Corrosion behavior of carbon steel, 1Cr steel, and 3Cr steel was evaluated using an autoclave with different combinations of CO2 partial pressure and temperature (8 MPa/25°C and 12 MPa/80°C) with 200 ppm H2S. The corrosion rate of samples was determined by weight-loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed using surface analytical techniques (scanning electron microscopy and energy dispersive x-ray spectroscopy). Results showed that the corrosion rate of materials in supercritical and liquid phase CO2 saturated with water was very low (<0.01 mm/y). However, adding 200 ppm of H2S to the supercritical and liquid CO2 system caused mild corrosion (<0.5 mm/y). Reducing water content to 100 ppm in the supercritical and li...