Antimicrobial And Corrosion Resistance Properties Of MoO₃-SiO₂ Composite Coating

The corrosion of metals brings huge economic losses and social harm to mankind.With the development of industry and science technology,the position of corrosion science in the national economy is becoming more and more important.In the marine environment,the main cause of metal corrosion damage is microbial corrosion and electrochemical corrosion.As a kind of containing molybdenum austenitic stainless steel,316L stainless steel（SS）exhibite high hardness,corrosion resistance and good corrosion resistance,it has been greatly improved than ordinary stainless steel,the uniform corrosion rate is very low and has been currently applied in the chemical industry,metallurgy,materials,medical and many other industries.But it is easy to occurring pitting and crevice corrosion in the environment of sea water,which can cause failure destruction of the equipment.Although there are many people studying the corrosion of metal materials,there are not many researches on 316L stainless steel specially.To solve this problem,the double cathodic glow discharge technology and ion oxidation technology were used to prepare composite coatings with compact structure and antibacterial properties on stainless steel surface,so as to provide guarantee for the use of stainless steel in marine environment.In this paper,MoO₃-SiO₂ nanocrystalline composite coatings on marine structural material 316L stainless steel were prepared by double cathodic glow discharge technology and ion oxidation technology.Scanning electron microscopy（SEM）,X-ray diffraction（XRD）and X ray photoelectron spectroscopy（XPS）were used to characterize the surface morphology,phase composition and elemental distribution of MoO₃-SiO₂ nanocrystalline composite coatings,and characterize the chemical valence states the elements,respectively.The antibacterial activity of MoO₃-SiO₂ composite coating was evaluated against gram-positive bacteria Streptococcus aureus（S.aureus）,gram-negative bacteria Escherichia coli（E.coli）and sulfate-reducing bacteria（SRB）.Antimicrobial properties of MoO₃-SiO₂ composite coating were measured by a spread plate method（SPM）.A comparative study on the electrochemical behaviors of uncoated 316L SS and MoO₃-SiO₂ coating immersed in Postgate′C seawater（PCS）medium with and without inoculated SRB for 7 days was carried out.Electrochemical measurements,including potentiodynamic polarization tests and electrochemical impedance spectroscopy（EIS）,were carried out to assess the corrosion resistance of the coating.Antibacterial rates（Ra）value of MoO₃-SiO₂ coating reached 80.7%for E.coli and 68.9%for S.aureus,respectively.And the resistance values of the MoO₃-SiO₂ coating were more than 10⁷¹0⁸Ω·cm² which is three order of magnitude higher than that of bare 316L SS.The obtained experimental findings showed that the MoO₃-SiO₂ composite coating not only provided 316L SS with good corrosion protection,but also endowed it with a better antibacterial property to microbiologically influenced corrosion.This indicated the potential utility of MoO₃-SiO₂ composite coating in the complex ocean environment.