Corrosion Behavior Of Ti-6Al-4V Alloy In Sulfate Reducing Bacteria

In the marine environment,microbiologically influenced corrosion is one of the main factors affecting the corrosion behavior of marine engineering materials.Among them,sulfate-reducing bacteria（SRB）has the most significant impact on the corrosion of marine engineering materials,and SRB is widely present in anaerobic environments such as soil,ocean,river and underground pipelines.At present,Ti-6Al-4V titanium alloy has been widely used in marine engineering equipment.The investigations show that Ti-6Al-4V titanium alloy has very good corrosion resistance in pure seawater,but Ti-6Al-4V titanium alloy has good biocompatibility,and these marine engineering equipment are immersed in seawater for a long time,which greatly exacerbates the possibility of Ti-6Al-4V titanium alloy being corroded by microorganisms,especially under the action of SRB bacteria,The corrosion possibility and severity of Ti-6Al-4V titanium alloy will be greatly increased.Therefore,it is very necessary to study the influence rule and corrosion mechanism of SRB on the corrosion behavior of Ti-6Al-4V titanium alloy,which will be the basis for the subsequent application of Ti-6Al-4V titanium alloy in marine engineering equipment.At present,there are many types of SRB found,there are more than 220 species in 60 species.Different types of SRB has different forms,and there is a large difference in the corrosion ability of metals.Among them,SRB belonging to the Desulfovibrio has the strongest corrosion ability to metals.The initial strains used in this study were provided by the Guangdong Provincial Microbial Culture Collection Center and belonged to the Desulfovibrio.After activating SRB and cultivating it,the growth curve of SRB was drawn by the turbidimetry method,and the adhesion behavior of SRB on the surface of Ti-6Al-4V titanium alloy was observed using a fluorescence microscope.The results showed that a small amount of SRB was adsorbed on the surface of Ti-6Al-4V titanium alloy soaking for 1d,a small amount of SRB colonies appeared on the surface of Ti-6Al-4V titanium alloy soaking for 2d,and a large amount of SRB adsorbed on Ti-6Al-4V titanium alloy surface soaking for 5d.The electrochemical behavior of sulfate-reducing bacteria on Ti-6Al-4V titanium alloy was studied by electrochemical methods such as open circuit potential,polarization curve and AC impedance spectroscopy.The results show that the metabolite of SRB accelerates the corrosion rate of Ti-6Al-4V titanium alloy when immersed for 0-1d.The dense titanium oxide film is formed on the surface of Ti-6Al-4V titanium alloy after immersion for 1-4d.Carried out,soaked for 4-31d,SRB metabolites and corrosion products destroyed the original oxide film,resulting in increased metal corrosion.When immersed for 31 days,the oxide film on the sample surface was greatly damaged,and the corrosion rate increased greatly.Scanning electron microscope（SEM）was used to observe the surface corrosion morphology of the sample soaked for 31 days,and X-ray fluorescence spectroscopy（XRF）was used to determine the element changes during the corrosion process,and X-ray photoelectron spectroscopy（XPS）was used to determine the final corrosion.The valence of elements in the product.The results show that SRB can promote the occurrence of pitting corrosion of Ti-6Al-4V titanium alloy,and Al（OH）₃ and a small amount of Ti S₂ are detected in the final corrosion products.This paper finally deduces the corrosion process of Ti-6Al-4V titanium alloy in SRB medium.