Corrosion Behavior of Arc-Sprayed Pore-Sealed Zn and Al Coatings in Seawater Containing Sulfate-Reducing Bacteria (SRB)

In this article, zinc and aluminum coatings were deposited on plain carbon structural steel (Q235) substrates by electric arc spraying. The coatings were then pore-sealed with a silicone resin to enhance their corrosion performance. The latter was tested in seawater containing sulfate-reducing bacteria by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. The tests showed that the pore-sealed Al coating had a superior corrosion resistance to the pore-sealed Zn coating in all the corrosion tests. The corrosion rates of the pore-sealed Zn coating first increased as the oxide film was easily destroyed. Then, they decreased as the corrosion products delayed the diffusion of the corrosive medium. On the other hand, the corrosion rates of the pore-sealed Al coating consistently decreased, most likely because of the protective effect of the dense Al 2 O 3 film formed at the early stage of immersion and biological film formed by SRB at the later stage of immersion.