Biotic sol-gel coating for the inhibition of corrosion in seawater

In marine environments corrosion is exacerbated by formation of destructive biofilms containing sulphate-reducing bacteria, which promote corrosion by forming corrosive species, such as H2S. Corrosion-causing biofilms are often resistant to inactivation by biocides since the biofilm bacteria are protected by a matrix of exopolymeric substances (EPS). Paradoxically, a biofilm of the endospore-forming Paenibacillus polymyxa can actually inhibit corrosion. Sol gel technology and immobilized microorganisms have been combined in a unique coating that inhibits corrosion on aluminium alloys, being low-cost, effective and environmentally friendly. Viability studies show that P. polymyxa endospores can withstand solvent concentration of up to 50% and an acid concentration of up to 1.5M and germinate within a biotic sol-gel coating. Electrochemical impedance spectroscopy and linear polarization resistance tests, in addition to an extended field trial, have shown that the endospore-loaded coatings show resistance to corrosion and biofilm formation relative to coatings without added endospores.