Corrosion inhibition by aerobic biofilms on SAE 1018 steel

Characterization of axenic Pseudomonas fragi and Escherichia coli biofilms that inhibit corrosion of SAE 1018 steel

“…fragi K or E. coli DH5a (pKMY319) was examined for 8 d in stationary batch cultures at 23°C and 30°C in which the growth medium was either replenished daily or left unchanged for 8 d. The metal coupons immersed in bacterial suspensions showed a 2·3-6·9-fold decrease in mass loss after 8 d compared with coupons immersed in sterile media (Table 1). These results compare well with those of Jayaraman et al (1997a) and Pedersen and Hermansson (1989) who Table 1 Four-day Pseudomonas fragi K batch culture biofilm values chosen as representative from one of four positions viewed at the same depth from a single coupon. The normalized depth position in the biofilm which is indicated corresponds to the approximate maximum cellular content (live and dead cells), and the % live cells, % dead cells, % EPS, and % void listed at this position are from COMOS data analysis (MRC 600 microscope) ---------------------------------------------------------------------------------------------------------------- reported an eightfold reduction in corrosion of SIS 1146 steel using Pseudomonas S9 and Serratia marscens after 19 days of exposure in VNSS medium.…”

“…The normalized depth position in the biofilm which is indicated corresponds to the approximate maximum cellular content (live and dead cells), and the % live cells, % dead cells, % EPS, and % void listed at this position are from COMOS data analysis (MRC 600 microscope) ---------------------------------------------------------------------------------------------------------------- reported an eightfold reduction in corrosion of SIS 1146 steel using Pseudomonas S9 and Serratia marscens after 19 days of exposure in VNSS medium. Previous work in this laboratory has shown that there is no difference in the corrosion of SAE 1018 steel coupons in sterile, fresh LB medium and spent, filtered LB medium (Jayaraman et al 1997a).…”

“…fragi K) (Jayaraman et al 1997a) and a tetracycline-resistant enteric bacterium, E. coli DH5a (pKMY319) (Jayaraman et al 1997a) were used, based on their ability to form biofilms (Parolis et al 1991;Huang et al 1993). Both strains were cultivated without shaking at 23°C or 30°C in 250 ml Erlenmeyer flasks with multiple SAE 1018 metal coupons in 35 ml of Luria-Bertani medium (LB, Maniatis et al 1982) and Vaatanen nine salts solution (VNSS, Hernandez et al 1994) supplemented with 50 mg ml −1 of kanamycin (Jayaraman et al 1997a) or 25 mg ml −1 of tetracycline (Yen 1991). All strains were streaked from a −85°C glycerol stock onto LB agar plates with appropriate antibiotics.…”

“…The specific mass loss observed (mg cm −2 ) was determined by dividing by the total surface area of the coupon (11·18 cm 2 ) and was used as an indicator of the extent of corrosion (Jayaraman et al 1997a). All corrosion experiments were performed with three replicates.…”

“…SAE 1018 steel coupons weighing 5·1 g and having a diameter of 25·5 mm and a thickness of 1·2 mm were cut from sheet stock, polished with 240 grit polishing paper (Buehler, Lake Bluff, IL, USA) and prepared as reported previously (Jayaraman et al 1997a). The specific mass loss observed (mg cm −2 ) was determined by dividing by the total surface area of the coupon (11·18 cm 2 ) and was used as an indicator of the extent of corrosion (Jayaraman et al 1997a).…”