ABSTRACT
ABSTRACT
The application of coatings has been a method used to prevent or control microbiologically influenced corrosion (MIC), mainly on carbon steel, a less corrosion resistant metal often used in various industries because of its low cost. This study aimed at evaluating comparatively the colonization and MIC on carbon steel AISI 1020, with and without a base coat of niobium oxide, in sea water (Guanabara Bay). The components of the coating – niobium oxide, epoxy and paint – presented toxic effects on the planktonic populations of aerobic heterotrophic bacteria (AHB), sulfate reducing bacteria (SRB) and iron precipitating bacteria (IPB), while anaerobic heterotrophic bacteria (AnHB) were not susceptible. Except for SBR that were present in low concentrations, at the end of the monitoring period (35 days) AnHB, IPB and AHB sessile numbers in biofilms of coated steel were 1, 2 and 5 orders of magnitude higher, respectively, than those numbers encountered on uncoated steel. The coated coupons showed no blistering or rusting evidence at the end of the experiments. The electrochemical tests showed the influence of bacteria on the current and corrosion potential of carbon steel, although few changes were detected when the metal was painted, what corroborates to the effectiveness of the niobium oxide coating on the protection of carbon steel.
