Pseudomonas putida RSS biopassivation of mild steel for long term corrosion inhibition

It is critical to develop highly tolerant, durable and efficient microbial corrosion inhibition methods for mild steel when use of chemical inhibitors is not feasible. Here, we developed a novel, long-lasting and commercially viable bacterial mediated corrosion inhibitive/biopassivating system for mild steel by employing Pseudomonas putida (P. putida) RSS biofilm. Enhancement in surface biopassivation was achieved by enhancing the biofilm formation in P. putida RSS culture when supplemented with 2.5% each of sucrose and potassium nitrate for a period of 96 h. The corrosion rate of mild steel could be decreased by 28 – fold when immersed in the optimized system in comparison to the control. This is due to the formation of a strong and stable iron-extracellular polymeric substance (Fe-EPS) coating over the concrete bacterial phosphate layer. The developed biofilm remained adhered on the surface of the mild steel surface even after the death of bacterial cells, and it conferred further protection. The corrosion resistance of mild steel surface after mechanically removing biofilm was also investigated. Results of electrochemical studies showed no traces of corrosion even after 12 months of immersion with negligible corrosion rate of 3.01 × 10⁻² mmpy. The developed surface biopassivation system can be employed for long term corrosion inhibition of steel structures in aquatic systems.