Applied Surface Science Advances (Dec 2023)
The potency of spores and biosurfactant of Bacillus clausii as a new biobased sol-gel coatings for corrosion protection of carbon steel ST 37 in water cooling systems
Abstract
The structures of water cooling systems are prone to microbially-influenced corrosion (MIC) due to the favorable conditions for microbial growth. Biofilm formation accelerates corrosion, leading to reduced system efficiency, structural damage, and significant financial losses. Encapsulating viable bacterial spores and biosurfactant within a silica-based sol-gel coating offers an eco-friendly approach to prevent this type of corrosion. Bacillus clausii, known for its antimicrobial biosurfactant production capability, was utilized in this study to investigate the impact of spores and biosurfactant addition to silica-based sol-gel coatings in inhibiting biofilm formation and preventing corrosion in water cooling systems. Microbiological analysis of the biofilm was conducted using the total plate count method, while the corrosion process was analyzed through electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The viability of B. clausii spores within the sol-gel matrix was determined to be 20.8 %. The presence of bacterial spores and biosurfactant significantly increased the hydrophobicity of the sol-gel coating. Incorporating spores within the sol-gel matrix delayed biofilm formation for up to 12 days, while biosurfactant addition showed the smallest biofilm abundance (2.23×105 CFU/mL) at its maturation phase compare to others. After 180 days of incubation, analysis of Bode and Tafel plots demonstrated that the sol-gel coating containing biosurfactant maintained excellent anti-corrosion performance, exhibiting an impedance of 104 Ω cm2, Ecorr of -0.398 V vs SCE, and icorr of 0.51 µA/cm2. SEM-EDS analysis of the surface sample revealed a comparably smooth and uniform surface with a minimal abundance of exposed Fe atoms at 0.12 %. In conclusion, this study demonstrated the high potency of the sol-gel coating supplemented with biosurfactant in inhibiting biofilm formation and corrosion on metals in water cooling systems.
