Papers by Keyword: Microbiological Influenced Corrosion (MIC)

Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with granular-Zn-epoxy and flaky-Zn-epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated with electrochemical impedance spectroscopy (EIS), X-rays diffraction (XRD), scanning electron microscope (SEM) etc. Results show that the protection effect of the flaky-Zn coating specimen is much better than the granular-Zn coating one. The dissolution of zinc is more severe in granular-Zn coating than in flaky-Zn coating when the specimen immersed in the SRB solution. The shielding property of flaky zinc is much higher than granular zinc in the coating. The flaky-Zn coating is much more compact than the granular-Zn coating and therefore the property of anti-infiltration is much better. We may conclude that the flaky-Zn coating exhibited more favorable corrosion resistance property than the granular one.

Abstract: The MIC behavior of the ship plate steel specimen with LaCl₃-Zn epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated in this paper. The variation of corrosion potential over time of different specimens in SRB solution show that the corrosion potential of the specimen with LaCl₃-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the LaCl₃-Zn epoxy coating may offer better protection. The variations of lgflg |Z|=4.5 and f_h with time show that the property of anti-infiltration and corrosion resistance of LaCl₃-Zn coating is much better than the ones of Zn-epoxy coating. Results also show that more sulfides and corrosion products of LaCl₃-Zn epoxy coating were produced which increased the shielding property of the coating. The experimental results of XRD and SEM are in good agreement with the ones of E_corr, and EIS, etc. They all show that the LaCl₃-Zn epoxy coating exhibits more favorable corrosion resistance property than the Zn-epoxy coating. It is obvious that coating the ship plate steel with LaCl₃-Zn epoxy is an effective and promising method against the attack of SRB in marine environment.

Abstract: In the present study, the rare earths element YbCl₃ was added into the Zn-epoxy coating, and the MIC behavior of the low alloy steel specimen with YbCl₃-Zn-epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated and compared with the specimen of Zn-epoxy coating. Experimental results show that both the YbCl₃-Zn-epoxy and Zn-epoxy coating may offer effective protection for the basic low alloy steel. However, the corrosion potential of the specimen with YbCl₃-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the YbCl₃-Zn-epoxy coating may offer more favorable protection. Results of X-rays diffraction (XRD) and surface micrographs of specimens show that more sulfides and corrosion products of YbCl₃-Zn-epoxy coating were produced which increased the shielding property of the coating. The mechanism about the effect of YbCl₃-Zn-epoxy coating on MIC behavior was further discussed.

Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with Zn-rich epoxy coating and micaceous iron oxide epoxy coating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated by using both full-coated and nicked-coated specimens. Results show that for steel coated with Zn-rich epoxy, the corrosion resistance of both full-coated and nicked-coated specimens was improved obviously. The Zn-rich epoxy coating protected the test steel effectively in the microbial environment with the cathodic protection in the earlier period and physical barrier protection in the later period. For steel coated with micaceous iron oxide epoxy coating, the corrosion resistance of full coated specimens was improved greatly. However, for nicked-coated specimens, corrosion was aggravated because the small anodic area around the nick accelerated the corrosion. It is concluded that the basic low alloy steel may be effectively protected by the micaceous iron oxide epoxy coating only when the steel is perfectly coated with the coating, breakage must be avoided.

Abstract: Effect of micaceous iron oxide epoxy coating on the microbiological influenced corrosion (MIC) behavior of the low alloy steel was studied. Samples uncoated or coated with micaceous iron oxide epoxy coating in sterile seawater and SRB solution was investigated by using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and so on. A series of data was obtained. Results show that micaceous iron oxide epoxy coating protected the base material effectively duo to its excellent physical barrier property.

Abstract: The microbiological influenced corrosion (MIC) behavior of the Cu-Ni alloy with or without Ni-P plating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the uncoated specimens in both the sterilized medium and the SRB solution when the specimens coated with Ni-P plating were still in good condition. Since the Ni-P plating may offer both barrier and cathodic protection to the base metal. Besides, the structures of Ni-P plating and the passive film on the surface of the Ni-P plating are high uniform and amorphous without any structure defects. The non-crystalline structure may improve the corrosion resistance because it does not have crystalline defects such as dislocation, grain boundary, twin and so on which may cause corrosion easily. It is concluded that corrosion behavior of the Cu-Ni alloy with electroless Ni-P plating was improved greatly.

Abstract: The microbiological influenced corrosion (MIC) behavior of a marine pipeline Cu-Ni alloy in the sterile seawater and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the specimens in the SRB solution. The corrosion potential of specimen in the SRB solution was much lower than that in the sterile seawater and the polarization resistance of specimen in the SRB solution decreased quickly after a period immersion and became much lower than that in the sterile seawater. Besides, the results of EDS and XRD show that the content of element Ni and Fe of the Cu-Ni alloy decreased greatly and the high content of element S appeared after 30 days immersion in the SRB solution. It was concluded that the SRB accelerated the corrosion process of the Cu-Ni alloy greatly. The MIC mechanism of the alloy in marine environment is discussed.

Abstract: The microbiological influenced corrosion (MIC) behaviors of the ship plate steel directly exposed in different medias (the sterile seawater, the ferrous bacteria solution and the sulfate-reducing bacteria solution) were investigated with electrochemical impedance spectroscopy (EIS), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Corrosion potential, electrochemical impedance and micrographs of specimens under different experimental conditions were obtained. Results show that the FB and SRB in the marine environment affect the corrosion behavior of the ship plate steel greatly. The corrosion process in FB and SRB environment was controlled by both bacteria and corrosion products. The mechanism of MIC is discussed.

Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with or without Zn-rich epoxy coating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated with electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and X-rays diffraction (XRD). Results show that the bacteria in the marine environment affect the corrosion behavior of the ship plate steel and the corrosion resistance of specimen coated with Zn-rich epoxy was improved greatly. The coating protected the test steel effectively in the microbial environment with the cathodic protection in the earlier period and physical barrier protection in the later period.