Electrochemical behavior of Zn‐REP nanohybrid coatings during marine Shewanella sp. biofilm formation

Abstract

Nanohybrid coatings, particularly zinc‐rich epoxy coatings, can protect steel from the harsh marine environment through a physical barrier mechanism and a cathodic protective effect based on anodic electrochemical reactions involving zinc particles in the coating. New additives, such as carbon nanotubes (CNTs), produce more efficient multifunctional coatings by enhancing both protective mechanisms. In this study, the electrochemical behavior and corrosion mechanisms of zinc‐rich epoxy nanohybrid coatings with the addition of CNTs were investigated in the presence of a Shewanella sp. marine strain to evaluate their influence on biofilm formation by this Gram‐negative bacterium. The electrochemical activity was monitored over time with open‐circuit potential, electrochemical impedance spectroscopy, and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy. A mixed mechanism was observed starting from early exposure. When the content of CNTs was doubled, the biofilm adherence improved, thus suggesting a favorable effect of CNTs on biofilm formation, attributable to increased production of bacterial exopolymeric substances facilitating biofilm development. The electrochemical impedance spectroscopy results suggested a correlation with biofilm formation as a second barrier layer with the lowest impedance magnitude in coatings with different multiwalled CNT content.

Formation ofEscherichia colibiofilms on the titanium alloy Ti6Al4V: analysis of the interface and assessment of corrosion

“…Similar results were reported by Zheng et al [53] in a study that was carried out with sulfate-reducing bacteria; similar to our results, this group reported an increase in R ct at the beginning of the monitoring period followed by a progressive decline at the end of the experiment. Similar behaviour was reported by Calvillo and Galicia [16], who presented impedance diagrams that illustrate times for adherence and attachment of Shewanella sp . in a marine biofilm.…”

“…Using open circuit potential (OCP) monitoring and electrochemical impedance spectroscopy (EIS), these researchers found that the biofilm that formed on the coated steel protected it from corrosion at the earliest time points in their experiments. More recently, Calvillo and Galicia [16] presented impedance diagrams that revealed adherence and attachment of Shewanella sp . and biofilm formation on coated carbon steel beginning at the first day of immersion; this was followed by biofilm detachment several days later.…”