Inhibition Behavior Of Lactobacillus Reuteri Extracellular Polymeric Substances On Carbon Steel Corrosion

Microorganisms can promote the corrosion reaction, but recent studies have found that microorganic extracellular polymer substance has inhibition on metal corrosion, but the field has just started and still in the exploratory stage.This paper mainly revoloes around Lactobacillus reuteri EPS effects on corrosion of carbon steel,Based on corrosion weightlessness method was used to compare the rate of carbon steel samples with and without of EPS corrosion, used scanning electron microscopy(SEM), X-ray diffraction(XRD) and other methods, studied EPS influenced carbon steel dirt morphology and fouling crystal composition;Adhibitioned of infrared spectrum(IR) to explore the EPS in inhibiting corrosion mainly play a major role in the process of functional groups;Applied of atomic force microscope(AFM) to analyze the change of EPS on carbon steel surface properties;Using spectrophotometer method to explore the EPS and iron ion reaction process on the carbon steel surface;This paper analysised of the EPS inhibiting corrosion mechanism of carbon steel prelininary.By comparing the presence of Lactobacillus reuteri EPS the change of the corrosion rate of carbon steel specimen indicated that, EPS made of carbon steel corrosion rate reduced by 25.60% on average, the corrosion weight loss decreased by 25.59%, Lactobacillus reuteri EPS have to inhibit the action of the corrosion of carbon steel.The surface properties of carbon steel specimens changed after soaking in Lactobacillus reuteri EPS, mainly affected the corrosion of the surface adhesion force, surface roughness and surface pore properties.EPS made carbon steel surface adhesion force decreased by 69.08%, the surface roughness was reduced by 70% or more, EPS effected the surface morphology formation " peak load shifting",the pore depth decreased by 74.51%, pore width was increased by 95.60%.EPS reacted with carbon steel surface before the corrosion reaction, changee the physical properties of the carbon steel surface, made the surface of carbon steel against corrosion.From the combination experiment which dextran simulate extracellular polysaccharide and bovine albumin simulation extracellular proteins with the iron trials get that: the ability of EPS, extracellular polysaccharide and extracellular proteins on the combination of iron ion is EPS > exopolysaccharide > extracellular protein, and these substances were more likely to react with ferric iron ion.In the process of Lactobacillus reuteri EPS formed EPS-Fe3+ layer on carbon steel surface, the functional groups took part in the reaction were polysaccharide O-H, amide C=O, carboxylic acid root COO-, polysaccharide C-OH, amide C-N, C-H and so on, such as polysaccharide O-H, carboxylic acid root COO- and C-OH groups as the main role.In the process of corrosion, the quantity of dirt on carbon steel specimens with EPS was significantly less than on the surface of carbon steel samples without EPS. Carbon steel specimens with EPS appeared corrosion circle, and later a closed shell corrosion products turned up, the corrosion circle was iron oxide, speculated that closed shell element was the GR1 green rust(Cl-) type by energy spectrum, the two forms of corrosion products all had protective effect on carbon steel specimens. With EPS dirt layer than carbon steel specimen without EPS samples dirt layer structure was more compact.Carbon steel specimens in water environment of corrosion producted crystal with Magnetite crystal(Fe3O4), Maghemite crystal(γ-Fe2O3), Lepidocrocite crystal(γ-Fe OOH) and Green rust crystal. Lepidocrocite have promote corrosion of carbon steel. Carbon steel specimen without EPS dirt layer osteoporosis oxygen content was higher, made green rust into lepidocrocite, lepidocrocite content increased further accelerated corrosion.Lactobacillus reuteri EPS inhibited of carbon steel corrosion behavior and mechanism:, extracellular polysaccharide O-H, COO- and C-OH as mainly functional groups reacted with ferric iron ion in the carbon steel passivation membrane after Lactobacillus reuteri EPS covering the surface of carbon steel, formed a dense and stable layer of EPS-Fe3+ protective layer. EPS-Fe3+ protective layer changed carbon steel surface physical properties,such as roughness, adhesion force and pore properties, made carbon steel surface against corrosion reaction.Due to the density of the EPS-Fe3+ protection layer stability, resisted cathodic depolarization agent such as the oxygen in the water reach the surface of the carbon steel, reduced the corrosion of carbon steel, at the same time, the corrosion circle and closed shell morphology corrosion products resulting from the presence of EPS had the effect of protection of carbon steel.Due to the decrease of oxygen, making the corrosion dirt not easily convert between crystal and dirt structure more stable solid.So as to slow down the corrosion of carbon steel.