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

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 809 ◽  
Author(s):  
Runzhi Qin ◽  
Yanxia Du ◽  
Zitao Jiang ◽  
Xiuyun Wang ◽  
Anqing Fu ◽  
...  
Keyword(s):  
Corrosion Behavior ◽  
Sandy Soil ◽  
Direct Current ◽  
Corrosion Mechanism ◽  
High Voltage Direct Current ◽  
Corrosion Reaction ◽  
Local Soil ◽  
X80 Steel ◽  
Remaining Time ◽  
Peak Value

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.

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

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yan-Yu Cui ◽  
Yong-Xiang Qin ◽  
Qing-Miao Ding ◽  
Yu-Ning Gao
Keyword(s):  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Sulfate Reducing Bacteria ◽  
Fluorescent Labeling ◽  
Corrosion Products ◽  
Economic Losses ◽  
Corrosion Mechanism ◽  
Sulfate Reducing ◽  
X80 Steel ◽  
Reducing Bacteria

Abstract Background At 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. Results The 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. Conclusion Although 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.

scholarly journals Coupling Effects of pH and Dissolved Oxygen on the Corrosion Behavior and Mechanism of X80 Steel in Acidic Soil Simulated Solution

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3175 ◽  
Author(s):  
Shuaixing Wang ◽  
Xiaole Yin ◽  
Hao Zhang ◽  
Daoxin Liu ◽  
Nan Du
Keyword(s):  
Dissolved Oxygen ◽  
Corrosion Behavior ◽  
Ph Value ◽  
Product Layer ◽  
Low Ph ◽  
Acidic Soil ◽  
Corrosion Mechanism ◽  
Coupling Effects ◽  
Effects Of Ph ◽  
X80 Steel

In an acidic red soil environment, the corrosion mechanism of X80 steel may be closely related to the pH value and oxygen content, but it has not yet formed a systematic understanding. In this paper, the coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in an acidic soil simulated solution were further analyzed by electrochemical methods and three-dimensional video microscope. Results showed that the hydrogen reduction reaction was almost the only cathode process in the anoxic and low pH system, and small and dense pits were present on the electrode surface. pH value increased, the pits decreased, but the size of pits increased. In the oxygen-adequate system, oxygen-consuming (OC) corrosion preferentially occurred, and a protective corrosion product layer (including FeOOH, Fe3O4, etc.) might be formed accordingly, but the proportion of hydrogen evolution (HE) increased and the product layer had defects at a low pH environment. The specific corrosion mechanism of X80 steel in an acidic soil simulated solution is described in the relevant models.

The corrosion behavior and cracking susceptibility of the disbonded coating in the X80 steel pipeline by theoretical simulations and experimental measurements

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Bo Zhao ◽  
Zhijuan Zhao ◽  
Dong Jin ◽  
Na Li ◽  
Linlin Liu ◽  
...  
Keyword(s):  
Diffusion Process ◽  
Corrosion Behavior ◽  
Electrode Reaction ◽  
Experimental Measurements ◽  
Accelerated Corrosion ◽  
Steel Pipeline ◽  
Corrosion Reaction ◽  
X80 Steel ◽  
Disbonded Coating ◽  
Theoretical Simulations

Abstract The corrosion behavior and cracking susceptibility of the disbonded coating in the X80 steel pipeline were investigated by different methods. The oxygen content in the trapped solution decreased rapidly with the formation of an airtight disbonded area. The airtight system affected the electrode reaction process, resulting in the inhibition of corrosion in the center of the disbonded area and the more refined surface finish of the sample. The bottom of the disbonded area underwent a relatively intense and accelerated corrosion reaction controlled by the diffusion process. The cracking susceptibility of the X80 steel firstly decreased and then increased in the pointing direction.

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