Evaluation of microbial corrosion of epoxy coating by using sulphate reducing bacteria

The deterioration of coatings by microbiological attack takes place directly or indirectly as a result of metabolic activity of microorganisms. The most severe bacterial corrosion occurs due to presence of sulphate reducing bacteria (SRB), as these produce hydrogen sulphide, leading to formation of metal sulphides and sulphates. Such type of microbiological corrosion can be controlled by incorporating suitable biocide in the coating. The objective of this study was to simulate such microbiological corrosion phenomena in the laboratory and observe its effect on the coating performance. In the present work, experiments were conducted to assess the antibacterial property of epoxy based anticorrosive coatings, with and without of biocide, by exposing them to SRB culture under anaerobic condition. Coal tar epoxy (CTE)-polyamide coating system which is known for superior antibacterial properties was selected as benchmark. The SRB effectiveness was evaluated by the formation of zone of inhibition in nutrient agar and visual observation. The surface morphology of coatings before and after exposure was analysed by scanning electron microscopy (SEM). The anticorrosive property of these coatings under SRB exposure was also monitored by measuring impedance of the coating by electrochemical impedance spectroscopy (EIS). The loss in adhesion after exposure was also measured for all the coatings. (C) 2016 Elsevier B.V. All rights reserved.