Study On Marine Microbiologically Influenced Corrosion Behavior And Corrosion Mechanism Of Fe-based Amorphous Coating

Corrosion is a huge problem faced in the application of marine engineering materials,and more than 20% of corrosion loss in metal is caused by microorganisms,so microbiologically influenced corrosion cannot be ignored.In order to reduce the impact of microbiological corrosion on engineering materials,the development of new anti-microbial corrosion coating materials is a meaningful subject.Fe-based amorphous coating is a surface material with excellent corrosion resistance and abrasion resistance,and has shown attractive application prospects in the field of marine engineering.However,the current research on the corrosion behavior of amorphous coatings is mainly concentrated in the conventional environment.The corrosion performance and corrosion mechanism of amorphous coatings in microbial environments are still unclear.In this paper,an Fe-based amorphous coating(Fe43.7Co7.3Cr14.7Mo12.6C15.5B4.3Y1.9)was prepared by supersonic flame spraying,and its microbiological corrosion behavior and corrosion mechanism in the marine bacterial environment were studied.X-ray diffraction(XRD),scanning electron microscope(SEM),fluorescence microscope(FM)were used for structural analysis of coatings and biofilms.Through polarization test,impedance test,noise test and other electrochemical methods and X-ray photoelectron spectroscopy(XPS),the microbiological corrosion behavior and mechanism of amorphous were studied.The corrosion behavior and corrosion mechanism of the Fe-based amorphous coating immersed in the solution inoculated with P.aeruginosa were comparatively studied.Cyclic polarization curve and impedance test results showed that P.aeruginosa reduced the polarization resistance of Fe-based amorphous coatings and increased the uniform corrosion rate.The electrochemical noise test showed that P.aeruginosa caused the pitting nucleation rate of the amorphous coating to double.The growth process of the passive film was studied by constant potential polarization and constant frequency impedance test.It was found that P.aeruginosa promoted the unstable growth of the passive film on the surface of the amorphous coating,which eventually led to the thinning of the passive film.XPS showed that P.aeruginosa accelerated the oxidation of metal elements in the passive film of the amorphous coating,resulting in the change of the composition of the passive film from dense low-valence metal oxides to high-valence and easily soluble loose oxides.At the same time,the biofilm hinderd the transfer of oxygen,so that the passive film cannot be repaired,resulting in a decline in the corrosion resistance of the amorphous coating.To improve the anti-microbial corrosion ability of coatings,electrodeposition of cuprous oxide,coating of superhydrophobic material,and coating of silicone hydrogel were used to treat amorphous coating.It was found that corrosion resistance of amorphous coating after the modification of superhydrophobic material and hydrogel was greatly enhanced,while corrosion resistance of amorphous coating modified by electrodeposited cuprous oxide was reduced.The antimicrobial properties of these three samples were characterized by the plate coating method.It was found that the antibacterial rate of the cuprous oxide modified amorphous coating reached 100%,and the antibacterial rate of the hydrogel modified amorphous coating was also higher than 99%,which both had good antibacterial effects.However,the antibacterial rate of the superhydrophobic surface modified coating was less than 1%.Therefore,considering comprehensive considerations,the modification of the Fe-based amorphous coating by hydrogel can achieve the best anti-corrosion and anti-fouling effect.Furthermore,the thickness was controlled by adjusting spraying times of amorphous coating(180 ?m,360 ?m)and hydrogel coating(50 ?m,100 ?m),combining to prepare four different thicknesses of amorphous modified coatings.Potential polarization and impedance testing were used to select the process with best corrosion resistance,that was,spraying a 360 ?m amorphous coating + 100 ?m hydrogel layer obtained best corrosion resistance and antibacterial effect.