Abstract: Biofilm is one of the main factors that influence metal corrosion in seawater environment.According to the structure and property of biofilm,a natural biopolymer gel,Calcium Alginate,an extracellular biopolymer containing carboxylate functional groups,was deposited on metal surfaces to form films.Simulated biofilm environment was produced.Corrosion behavior of carbon steel A3,low-alloyed steel E2,10CrMoAl and 1Cr18Ni9 stainless steel was studied by various electrochemical method,including measurements of corrosion potential, polarization curves, and electrochemical impedance spectra.Film coated sample surface was characterized by ESEM.The results show that such an approach is informative to reveal “how” and “to what extent” biofilm influences metal corrosion process during intial biofilm forming stage.