Degradation of metals due to corrosion causes serious economic problems throughout the world, and different corrosion protection techniques are being used to extend the service life of metallic structures.It has been suggested that some microorganisms can inhibit electrochemical corrosion of metals.Here we isolated a new marine inhibitory bacterium, Vibrio neocaledonicus sp., and EIS results showed that the corrosion resistance of carbon steel increased by more than sixty fold in the presence of this bacterium.This is the highest corrosion inhibitory effect reported for bacteria and is comparable with some industrial coatings such as electroless Ni.The inhibitory effect caused by the formation of an inhibitory layer which covers entire metal surfaces in the gust hours of attachment.The consumption of oxygen by electron transport proteins also reduced the cathodic reaction.FTIR and XPS analysis showed that the inhibitory layer is composed of Fe-EPS (Extracellular polymeric substances) complexes and strengthens by exposure time.To understand the EPS effect on the corrosion inhibition of carbon steel;EPS extracted by the bacterium and the inhibitory effect was examined by electrochemical methods.It is found that EPS has the significant inhibitory efficiency against corrosion of carbon steel in artificial seawater.Hence, we propose Vibrio neocaledonicus sp.and its EPS can be used as a new, natural, non-toxic, and cost-effective system for controlling corrosion processes of carbon steel.