Inhibiting Effect Of Vibrio Neocaledonicus Sp. And It’s Exopolysaccharide For Q235in Seawater

Metal material corroded easily by aggressive ions andmicroorganism inmarine surroundings. Microbiologically induced corrosion(MIC) was knownand studied for many years.Some bacteria will accelerate material corrosion asthe bacteria production and metabolic processes, while some bacteria couldprevent corrosion.This paper presents the inhibitory properties of a marineisolated bacterium namely, Vibrio neocaledonicus sp. and it’s exopolysaccharide(EPS) on the corrosion of carbon steel in artificial seawater for the first time.This paper studied the corrosion behavior of carbon steel Q235in artificialseawater without and with bacteria after different times by eletrochemistrytechnology, surface analyse technology and spectrum. From the result of EIS,the charge transfer resistance is almost40times higher in the presence of thisbacterium after24hours exposure which increased up to60times after10days compared to sterile artificial seawater. This is the highest inhibitory effect thathas been reported by bacteria. FT-IR results showed the presence ofcarbohydrate and protein as the components of EPS on the metal surfaces.FESEM images revealed that a homogenous layer covered the Q235surfacesafter6h and thickened by exposure time. CLSM images also showed thepresence of bacteria and biofilm on the metal surface which increased byexposure time. There was no corrosion production on carbon steel surface afterexposoed in seawater with bactera after30days and no pitting after polished.Howerver there was too much corrosion production on Q235surface whichexposed in blank solution.The inhibiting effect of exopolysaccharide(EPS) extracted from Vibrioneocaledonicus sp. and synergy with KBr,KI on carbon steel Q235has beenstudied by potentiodynamic polarization, electrochemical impedancespectroscopy (EIS) and scanning electronic microscopy (SEM). The resultsshowed that EPS could inhibit effectively the corrosion for Q235in0.5M H2SO4solution because of the formation of Fe-EPS coationg on carbon steel.Theinhibition rate reached the maximum when the concentration of EPS was1000ppm. The inhibition effect could increase when added KBr,KI.The absorption ofEPS or1000ppm EPS added KBr,KI respectively on Q235carbon steel waschemisorption and obeyed to the Langmuir adsorption isotherm. The componentof EPS was identified by using FTIR. In order to test the inhibiting effect of EPS for Q235carbon steel indifferent sulition, seawater was chosen as solution.This inhibition was studiedusing potentiodynamic polarization, EIS and SEM. The results showed that EPScould inhibit effectively the corrosion for Q235in seawater solution because ofthe formation of Fe-EPS coationg on carbon steel.The inhibition rate reached themaximum when the concentration of EPS was5g·L-1.