Sha Cheng

Electrochemical behavior of microbiologically influenced corrosion on Fe3Al in marine environment

In this article, microbiologically influenced corrosion behavior of Fe 3 Al intermetallic compound in microorganism culture medium has been investigated by using weight loss methods, electrochemical techniques, and electron microscopy. Polarization curves showed that a sharp electrical current peak caused by surface pitting could be observed after Fe 3 Al electrodes were immersed in culture medium for 15 days when the polarization potential was about −790 mV vs SCE. Based on the electrochemical impedance spectroscopy (EIS) and the equivalent circuit parameters of the associated system, the corrosion products were found to exhibit a two-layer structured feature and the microorganisms could induce pitting and erosion corrosion of the inner layer. In addition, the passivating film of the inner layer was absolutely destroyed by microbial metabolic products.

THE ELECTROCHEMICAL BEHAVIOR OF OCEANIC MICROBIOLOGICAL INFLUENCED CORROSION ON CARBON STEEL

The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.

Study of Fe3Al Corrosion Behavior in Simulating Marine Biofilm Environment

Calcium Alginate is a kind of natural biopolymer which can be deposited on metal surfaces to form film. In this work, microbe film was simulated by Calcium Alginate gel, according to the natural structure and property of microbe film. Acetic acid, manganese dioxide, and sodium sulfide were added separately in sodium chloride solution to simulate different bacteria culture systems. The corrosion behavior of Fe3Al was investigated in simulating biofilm environment by open circle potential, polarization curves, and electrochemical impedance. Electrochemical results show that the passivating film formed immediately when Fe3Al electrodes exposed in simulated seawater. The corrosion process of Fe3Al in the medium with manganic sediment was mainly dominated by oxygen diffusion. In the simulated environment with acetic acid, the pitting corrosion potential on the surface of Fe3Al moved towards negative accompanied with the increasing concentration of chlorine ion and the decreasing value of pH. Simulated sulphate reduce bacteria (SRB) accelerated cathodic polarization process of Fe3Al surface, corrosion potential dropped sharply and the surface oxidative membrane broken when polarization potential reached −0.5 V, indicating that Fe3Al can be easier corroded by SRB than by other bacteria.

Super-Hydrophobic Surfaces Improve Corrosion Resistance of Fe3Al-Type Intermetallic in Seawater

A novel super-hydrophobic film was prepared by myristic acid (CH3(CH2)12COOH) chemically adsorbed onto the polyethyleneimine (PEI) coated Fe3Al-type intermetallic wafer. The film character and structure were probed with contact angle measurement, scanning electron microscopy (SEM) and atomic force microscope (AFM). The results suggest that the structure of the film is similar to lotus and the seawater contact angle is larger than 150◦. Moreover, the corrosion resistances of untreated and modified samples in seawater were investigated by electrochemical impedance spectroscopy (EIS). Experimental results show that the corrosion rate of Fe3Al-type intermetallic with super-hydrophobic surface decreases dramatically because of its special microstructure.

Microscopical Observation of the Marine Bacterium Vibrio Natriegeus Growth on Metallic Corrosion

Biofilm formation and the adsorption of nonsulfate-reducing marine bacterium Vibrio natriegens (V. natriegens) to different metallic surfaces have been studied by atomic force microscopy (AFM). The nature of extracellular polymeric substance (EPS) has been monitored through the force-distance curve. EPS may act as adhesive binding adjacent cells and thus further enhance the aggregation of microbes during cluster formation due to its adhesiveness in nature. The AFM images supplied the change of the morphology of microbial cells and colonies, the distribution of microbial colonies, and the presence of EPS on the surfaces with immersion. Results showed that the biofilms formed on the surfaces increased in thickness and heterogeneity with time and that 3–7 days was the proliferation period of the bacteria on metallic surfaces. The corrosion type of the metals by V. natriegens could be confirmed as typical pitting attack through scanning electron microscopy (SEM) observation.

The Electrochemistry Corrosion Behavior of Fe3Al-Type Intermetallic with Super-Hydrophobic Surfaces

A novel super-hydrophobic film was prepared by myristic acid (CH3(CH2)12COOH) chemically adsorbed onto the polyethyleneimine (PEI) coated Fe3Al-type intermetallic wafer. The film character and structure were probed with contact angle measurement, scanning electron microscopy (SEM), and atomic force microscope (AFM). The results suggest that the structure of the film is similar to lotus, and the seawater contact angle is larger than 150°. Moreover, the corrosion resistances of untreated and modified samples in seawater were investigated by electrochemical impedance spectroscopy (EIS). Experimental results show that the corrosion rate of Fe3Al-type intermetallic with super-hydrophobic surface decreases dramatically because of its special microstructure.

Microbially Influenced Corrosion of Copper by Marine Bacterium Vibrio natriegens

The microbially influenced corrosion of copper by marine bacterium Vibrio natriegens (V. natriegens) was investigated using surface analysis (atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). AFM images corroborated the results from the EIS models which show biofilm attachment over time. The electrochemical results showed that the corrosion of copper was accelerated in the presence of V. natriegens based on the decrease in the resistance of the charge transfer resistance (Rct) obtained from EIS.

Electrochemical Corrosion Behavior of Cu-15Ni-8Sn Alloy in Marine Microbial Medium

A comparative study of the corrosion behavior of the copper-nickel-tin alloy in a nutrient–rich simulated seawater-based nutrient-rich medium in the presence and the absence of the marine bacteria was carried out by electrochemical experiments, microscopic methods. Comparing to the corresponding control samples, the electrochemical data demonstrated that the presence of the bacteria accelerated the corrosion of the alloy. Scanning electron microscopy (SEM) images revealed the occurrence of micro-pitting and intergranular corrosion underneath the biofilm on the alloy surface.

Quantum Chemical and Electrochemical Studies on the Inhibitive Effect of Carboxymenthylchitosan for Mild Steel in Different PHs

The influence of carboxymenthylchitosan(CM-chitosan) on the corrosion of mild steel in different pHs was studied by the quantum chemical calculation and electrochemical measurements. Mulliken atomic charges and LUMO energies calculated by DFT method for CM-chitosan and protonated CM-chitosan show that the protonated CM-chitosan adsorbs easier on the surface of mild steel. The expeimental results of polarization curves and electrochemical impedance spectroscopy (EIS) also indicate that the acid media has the best inhibition efficiency for CM-chitosan. Furthermore, the inhibitive effect of CM-chitosan for mild steel in 1 M HCl solution was studied by weight loss measurements, and the inhibition efficiency increases with the concentration of CM-chitosan to attain 93 % at 200mg/l.

Investigation on Fe3Al Corrosion Behavior in Simulating Marine Biofilm Environment

In terms with the natural structure and property of microbe film, microbe film was simulated by Calcium Alginate gel Acetic acid, manganese dioxide, sodium sulfide were added separately into sodium chloride solution to simulate different bacteria culture systems. The corrosion behavior of Fe3Al was characterized based on the analysis of open circle potential, polarization curves, and electrochemical impedance. The corrosion potential of simulating SRB was 0.6V negative-moved in comparison with that of the other two bacteria. The results indicate that Fe3Al electrodes were much easier eroded by SRB environment.