Kinetic and thermodynamic studies of microbial corrosion of mild steel specimen in marine environment

Central State University, Wilberforce, Ohio, USA

B. J. B. College. Bhubaneswar, India

E-mail : chittardas@yahoo.com

Manuscript received I September 2004, accepted 5 January 2005

The kinetic and thermodynamic studies of microbial corrosion reaction on the surface of mild steel in 3% sodium chloride solution have demonstrated that the adsorption of nutrient molecules over the mild steel surface is exothermic, but the adsorption is found to be endothermic in the presence of bacteria. In the absence of bacteria, the increasing concentration of nutrient medium has increased the surface coverage and inhibited the corrosion damage us evinced by the increase in overall activation energy of the corrosion reaction. Addition of bacteria, Pseudomonas aeruginosa has probably depleted the adsorbed nutrient molecules and uncovered the active sites to be accessed to the corrosive medium and thus, accelerated the corrosion reaction. The attachment of bacterial slime has probably hindered the transport of oxygen molecules to the metal surface and developed distinct anodic and cathodic areas which resulted in localized corrosion by forming differential aeration cell.