Abstract:Multifunctional coatings for corrosive environments have been developed to include two basic principle protection mechanisms: a barrier mechanism acting as a mass transfer process blocker, and cathodic protection mechanism acting as a charge transfer process promoter. Both mechanisms were assessed for Zinc-Rich Epoxy (ZRE) coatings in the presence of Carbon Nanotubes (CNTs) and exposure to a bioelectrolyte in order to study the evolution process during microbial corrosion conditions. The purpose of this study … Show more
“…in a marine biofilm. Our findings were also analogous to those of Castaneda and Galicia [17] who identified an extra biolayer originating from a sulfate-reducing bacterial consortium based on the synthesis and release of EPS that influenced the homogeneous biolayer. Figure 3 Diagram of biofilm formation based on measured impedance parameters, including (a) R ct-b vs. time and (b) C dl vs .…”
Section: Resultssupporting
confidence: 89%
“…Charge transfer resistance decreased from 24 to 40 h, which suggests detachment of the biofilm and an increase in the rate of corrosion. Similar findings were reported in previous studies that focused on the assessment of corrosion of coatings in an electrolyte solution with a bacterial consortium [17]. However, a slight stabilisation of the impedance parameter was detected at 48 h, which may denote the formation of a new biofilm at the metallic surface.…”
Section: Characterisation Of the E Coli Biofilm By Semsupporting
confidence: 90%
“…Collectively, these results revealed enhanced resistance to corrosion and suggested that marine biofilms promoted a barrier against the active dissolution of carbon-coated steel. Similar electrochemical behaviour was described by Castaneda and Galicia [17] in their description of an extra biolayer that formed on a coating surface that originally resulted from the actions of a sulfate-reducing bacterial consortium. In this case, the researchers found that bacterial secretion of EPSs resulted in the formation of a more homogeneous biolayer that served as a barrier against corrosion.…”
Section: Introductionsupporting
confidence: 74%
“…All fixation and washing steps were conducted at room temperature. After fixation, the cells were washed twice in PBS and then re-suspended in sterilised ultrapure water to avoid salt crystallisation during the drying process [17]. Finally, the samples were spattered with silver particles and observed by energy-dispersive spectroscopy under a JSM-7000F/ JOEL microscope operated at 3-5 kV.…”
Section: Sample Preparation For Electron Microscopymentioning
Bacterial biofilm that formed when the Ti6Al4 V alloy was exposed to Escherichia coli, was monitored over 48 h by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) to estimate the rate of corrosion and the influence of the bacteria on this process. High-resolution scanning electron microscopy was used to examine bacterial growth, colonisation and the process of biofilm formation. Our results highlighted several critical points regarding the impact of E. coli and its use as a model for monitoring biofilm formation and the biocorrosion of this alloy. Impedance spectra revealed the formation of a compact passive film after 48-hour exposure to an aging culture of E. coli in chloride media. The formation of the biofilm influenced the resistance to corrosion. Biofilm impedance parameters that emerged over time corresponded directly to the properties of a typical exponential bacterial growth curve determined by ultraviolet-visible light spectroscopy.
“…in a marine biofilm. Our findings were also analogous to those of Castaneda and Galicia [17] who identified an extra biolayer originating from a sulfate-reducing bacterial consortium based on the synthesis and release of EPS that influenced the homogeneous biolayer. Figure 3 Diagram of biofilm formation based on measured impedance parameters, including (a) R ct-b vs. time and (b) C dl vs .…”
Section: Resultssupporting
confidence: 89%
“…Charge transfer resistance decreased from 24 to 40 h, which suggests detachment of the biofilm and an increase in the rate of corrosion. Similar findings were reported in previous studies that focused on the assessment of corrosion of coatings in an electrolyte solution with a bacterial consortium [17]. However, a slight stabilisation of the impedance parameter was detected at 48 h, which may denote the formation of a new biofilm at the metallic surface.…”
Section: Characterisation Of the E Coli Biofilm By Semsupporting
confidence: 90%
“…Collectively, these results revealed enhanced resistance to corrosion and suggested that marine biofilms promoted a barrier against the active dissolution of carbon-coated steel. Similar electrochemical behaviour was described by Castaneda and Galicia [17] in their description of an extra biolayer that formed on a coating surface that originally resulted from the actions of a sulfate-reducing bacterial consortium. In this case, the researchers found that bacterial secretion of EPSs resulted in the formation of a more homogeneous biolayer that served as a barrier against corrosion.…”
Section: Introductionsupporting
confidence: 74%
“…All fixation and washing steps were conducted at room temperature. After fixation, the cells were washed twice in PBS and then re-suspended in sterilised ultrapure water to avoid salt crystallisation during the drying process [17]. Finally, the samples were spattered with silver particles and observed by energy-dispersive spectroscopy under a JSM-7000F/ JOEL microscope operated at 3-5 kV.…”
Section: Sample Preparation For Electron Microscopymentioning
Bacterial biofilm that formed when the Ti6Al4 V alloy was exposed to Escherichia coli, was monitored over 48 h by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) to estimate the rate of corrosion and the influence of the bacteria on this process. High-resolution scanning electron microscopy was used to examine bacterial growth, colonisation and the process of biofilm formation. Our results highlighted several critical points regarding the impact of E. coli and its use as a model for monitoring biofilm formation and the biocorrosion of this alloy. Impedance spectra revealed the formation of a compact passive film after 48-hour exposure to an aging culture of E. coli in chloride media. The formation of the biofilm influenced the resistance to corrosion. Biofilm impedance parameters that emerged over time corresponded directly to the properties of a typical exponential bacterial growth curve determined by ultraviolet-visible light spectroscopy.
Nanohybrid coatings, particularly zinc‐rich epoxy coatings, can protect steel from the harsh marine environment through a physical barrier mechanism and a cathodic protective effect based on anodic electrochemical reactions involving zinc particles in the coating. New additives, such as carbon nanotubes (CNTs), produce more efficient multifunctional coatings by enhancing both protective mechanisms. In this study, the electrochemical behavior and corrosion mechanisms of zinc‐rich epoxy nanohybrid coatings with the addition of CNTs were investigated in the presence of a Shewanella sp. marine strain to evaluate their influence on biofilm formation by this Gram‐negative bacterium. The electrochemical activity was monitored over time with open‐circuit potential, electrochemical impedance spectroscopy, and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy. A mixed mechanism was observed starting from early exposure. When the content of CNTs was doubled, the biofilm adherence improved, thus suggesting a favorable effect of CNTs on biofilm formation, attributable to increased production of bacterial exopolymeric substances facilitating biofilm development. The electrochemical impedance spectroscopy results suggested a correlation with biofilm formation as a second barrier layer with the lowest impedance magnitude in coatings with different multiwalled CNT content.
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