Bacillus sp.-triggered biocorrosion of arc sprayed aluminum coatings in artificial seawater

Thermal sprayed marine coatings in the marine environment encounter both chloride- and microbiologically induced corrosion. Formation of microbial biofilm is crucial for attachment of large foulers and understanding the initiation and growth of the biofilm is essential for possibly controlling occurring of biofouling. Here we report the formation of Bacillus sp. bacterial biofilm on arc sprayed aluminum coatings and its effect on their corrosion behaviors. Results show fast attachment and colonization of the bacteria on the coatings. The bacterial biofilm was systematically examined by AFM, CLSM, FESEM, and Raman spectroscopy. 90 days immersion already triggered remarkable pitting corrosion. A model was proposed to explain how the microorganisms and their metabolic by-products protect the coatings against penetration of corrosive media. In addition, effect of shear stress generated by laminar and weakly turbulent flow on adhesion of the bacteria and formation of biofilm was further studied by numerical simulation and morphological observation. Development of the bacterial biofilm in early stage was unaffected by the shear stresses. However, shear stress decides the disposition of the bacteria to interact with the sample surface. The results would give insight into design and fabrication of thermal sprayed coatings for enhanced anti-biocorrosion performances in the marine environment.