This study aims to evaluate the morphology of biofilms formed on the surface of API 5L X80 steel exposed to a low BSW (Basic Sediment Water) fluid comprising oil of a low water content. The analisys was performed using scanning electron microscopy (SEM) in order to determine the formation kinetics, to quantify and identify the bacterial groups present as the film formed, and to evaluate the biocorrosion caused by these organisms. Modifications were made to the original sample preparation protocol, in order to better define the film morphologies. Studies were undertaken applying either static or dynamic (looping) conditions, bith with and without the addition of biocides. The process fluid used was oil collected from the Petrobras Barra do Furado Terminal, characterized by its 1 percent BSW. The evaluation was performed quantifying the sessile bacteria present in the film (heterotrophic bacteria, iron bacteria, anaerobic bacteria e sulphate reducing bacteria) via the Most Probable Number (MPN) technique. The intensity of the corrosion process was determined by the analysis of pits forme in the testpieces, by optical microscopy. The application of a sample fixation sequence, in addition to modifications of the inicial sample preparation protocol, permitted the improved preservation of the biofilm structures, thereby permitting higher resolution images. The primary fixing agent, containing gluteraldehyde, principally fixes proteins, by establishing divalent bonds with amino groups, while the post-fixation stage with osmium tetroxide invloves reactions with lipid groups.With regard to the film deposition kinetics, it was observed that biofilm formation could only be detected after 15 day s exposure to the oily fluid. The addition of a biocide, inhibited the growth of the film, no cultivatable cells being present after 7 days contact with the treated fluid.