Severe Pitting Corrosion of Carbon Steel Caused by Sulfate Reducing Bacteria in Aqueous Medium
Severe Pitting Corrosion of Carbon Steel Caused by Sulfate Reducing Bacteria in Aqueous Medium
Sanaullah Sattar1, Ali Hussain2*, Javed Iqbal Qazi2, Arshad Javid1 and Shahid Mehmood1
ABSTRACT
The current study was conducted to assess the corrosive action of SRB on carbon steel coupons in aqueous media with and without the addition of nutrients of Postgate B medium. For the purpose, SRB strain was isolated from a highly polluted wastewater stream flowing in Lahore, Punjab, Pakistan. The bacterial isolate was motile, Gram-negative, non-spore former and identified as Desulfovibrio vulgaris after 18 S rRNA gene sequencing. The corrosive action of the bacteria was assessed in a 60-day trial of anaerobic incubation. After an incubation period of 60 days, it was found that CR was significantly higher for the coupons that were dipped in inoculated media. For these coupons, the average CR appeared as 210 ± 17 µg dm−2 d−1. However, CR was significantly lower (210 ± 17 µg dm−2 d−1) for the coupons dipped in inoculated water only (Fig. 2). In un-inoculated vials having nutrients, CR appeared higher (97 ± 16 µg dm−2 d−1) as compared to those without nutrients (48 ± 21 µg dm−2 d−1). Bacterial growth appeared higher in nutrient added vials. At termination of the experiments, total viable counts for SRB were 2.7 ± 0.3 × 109 CFU mL−1 in vials supplemented with nutrients. However, no bacterial growth was seen in nutrient-deprived vials. No change in pH was observed in all vials except those which were inoculated under optimum provision of nutrients. In these vials, pH changed from neutral to slightly basic in range (7.0 ± 0.5 to 6.0 ± 0.5). SEM analysis of the coupon which was recovered from a vial supplemented with nutrients revealed severe pitting corrosion of the steel coupon. Our findings will be helpful in understanding and protecting bacterial corrosion of water-dipped metallic bodies.
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