Vibrio neocaledonicus Sp., a Novel Marine Bacterium with the High Corrosion Inhibition Efficiency

Many marine steel structures, such as harbor and oil exploration facilities become corroded over time and need to be renovated or modified, which is expensive. Therefore, it is essential to extend the service life of the existing structures using appropriate methods. Current corrosion protection techniques usually involve toxic or expensive applications, such as volatile organic compounds, which are considered to be a major human health issue or expensive elements incorporated for a stainless steel effect. These limitations have prompted a greater interest in developing alternative methods for corrosion protection. The most promising approaches to achieve effective environmentally friendly corrosion control are to avoid the use of biocides or other traditional strategies. The inhibitory effects of bacteria were shown for the first time in 1988 in that bacteria could reduce corrosion rate of carbon steel. In this study, from a marine environment, we isolated a new inhibitory bacterium namely Vibrio neocaledonicus sp.  which increased the corrosion resistance by more than 60-fold. This is the highest corrosion inhibitory effect that has been reported by bacteria. This inhibitory effect is stable as long as the growth medium is refreshed. This capacity was comparable with some industrial coatings such as electroless Ni-P or Ni-P-PTFE. FTIR analysis confirmed the formation of iron-EPS complexes on a metal surface as EPS is adsorbed on the surface as an inhibitory layer and provides the first inhibitory effect. EPS adhered to metal surfaces by the functional groups of an exopolymer substance. FTIR spectra detected the presence of carbohydrates and amide groups in the EPS structure which enable EPS adhere irreversibly to metal surfaces.