Assessing the Anticorrosion and Antifouling Performances of a Sol–Gel Coating Mixed with Corrosion Inhibitors and Immobilised Bacterial Endospores

Abstract

The encapsulation of corrosion inhibitors in sol–gel coatings is a practical method for protecting mild steel against corrosion. Another recent approach involves the localization of a biologically active reagent close to the metal substrate. In this study, we have utilized the above two approaches in developing bacteria and inhibitor-doped sol–gel protective antifouling coatings on mild steel substrates. Molywhite$^\mathrm{TM}$ and Heucophos ZAPP$^\mathrm{TM}$ have been selected to be mixed with Paenibacillus polymyxa endospores within a base sol–gel coating composed of TEOS and METEOS and then applied on mild steel panels. The corrosion inhibition efficiency of the coatings was evaluated using electrochemical impedance spectroscopy and scanning electron microscopy techniques. After immersion in open seawater or marine estuarine water for 10 weeks, coatings containing endospores of P. polymyxa bacterial strain alone gave superior corrosion and antifouling protection than coatings containing corrosion inhibitors alone or corrosion inhibitors with endospores.