Abstract
Carbon steel (CS) coupons covered with an artificial biofilm—which consisted of 0.6% agarose and diluted activated sludge (150 mg/L) from a municipal wastewater plant—were exposed to synthetic wastewater. When only one side of the coupon was covered with the artificial biofilm, mass loss of the steel coupon reached 0.46 mg/cm2-day. Complete insulation of both sides with the artificial biofilm resulted in CS corrosion of 0.16 mg/cm2-day. Structural analysis of this artificial biofilm, using microelectrodes for measuring dissolved oxygen (DO) and pH, revealed that disproportionate distribution of DO and pH in the biofilm enhanced CS corrosion, and a rapid decrease in the DO concentration in the zone near the surface of the biofilm was observed when both sides of the steel coupon were covered with the biofilm. Complete consumption of the oxygen from the biofilm delayed steel oxidation. However, pH decrease and sluggish decrease of DO in the film were observed when only one side of the steel coupon was covered with the artificial biofilm. These observations indicate that complete polarization caused by biofilm formation on the steel surface enhances the microbiologically influenced corrosion (MIC) of CS.
