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.
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 electrochemical 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 of the sample 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 promoted 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 Fe oxides. 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.
The influence of ultraviolet rays on the corrosion behavior of 7075 aluminum alloy in the marine atmosphere was studied by salt spray corrosion test. Electrochemical methods and surface analysis techniques were used to analyze and compare the corrosion laws of 7075 aluminum alloy in the marine atmosphere under ultraviolet radiation with wavelengths of 0 nm, 185 nm, 254 nm, and 365 nm. The results showed that ultraviolet light irradiation could promote the corrosion of 7075 aluminum alloy. Oxygen was prone to chemical reactions to form oxygen atoms after being irradiated by ultraviolet rays, and oxygen atoms recombined with oxygen to form ozone in the marine atmosphere. The 7075 aluminum alloy in the marine atmosphere accelerated corrosion due to the increasing ozone content. Although there were passivation films with different degrees of protection on the surface of aluminum alloy under ultraviolet irradiation, the surface of 7075 aluminum alloy in the marine atmosphere failed to form a stable passivation film after pitting, and the corrosion rate was the fastest when the ultraviolet wavelength was 185 nm.
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