Abstract
Taiwan is an island with a humid subtropical climate. The relatively warm seawater results in biofouling of the surfaces of marine facilities. Biocide application is a common practice for combating and eliminating adhesive fouling. However, a single type of biocide may have limited antimicrobial effects due to the relatively high microbial diversity in marine environments. Therefore, applying a mixture of various biocides may be necessary. In this study, the antimicrobial and anticorrosion properties of a newly designed composite biocide, namely a combination of thymol and benzyldimethyldodecylammonium chloride, were investigated by applying the biocide to 304 stainless steel substrates immersed in inocula containing bacterial strains from Tamsui and Zuoying harbors. The ability of 3TB and 5TB treatments to prevent sessile cells and biofilm formation on the 304 stainless steel coupon surface was determined through scanning electron microscopy investigation. In addition, confocal laser scanning microscopy indicated that the 5TB treatment achieved a greater bactericidal effect in both the Tamsui and Zuoying inocula. Moreover, electrochemical impedance spectroscopy revealed that the diameter of the Nyquist semicircle was almost completely unaffected by Tamsui or Zuoying under the 5TB treatment. Through these assessments of antimicrobial activity and corrosion resistance, 5TB treatment was demonstrated to have superior bactericidal activity against mixed strains in both southern and northern Taiwanese marine environments.
Highlights
Corrosion is a common phenomenon that leads to the failure of engineering materials in marine environments
Determination of the minimum inhibitory concentrations (MICs) of Composite Biocides To determine the MICs of the composite biocides, the O.D.600 of the Tamsui and Zuoying inocula were measured separately over 36 h
The antimicrobial activity of different concentrations of composite biocides were evaluated against two inocula
Summary
Corrosion is a common phenomenon that leads to the failure of engineering materials in marine environments. The effect of microbiologically influenced corrosion should not be overlooked. The failure of materials due to microbiologically influenced corrosion is mainly attributable to the formation of biofilms containing mixed microorganisms. Influenced corrosion is an electrochemical process involving interactions among microorganisms, metals, and the corrosive environment. Numerous researchers have made progress in studying the corrosion behavior and interactions in a mixed system of SRB/IOB [16,17] and SRB/NRB [18,19]. The literature indicates that the synergistic action of mixed bacterial strains exerts a strong corrosive effect on metals. Biofilms formed by mixed strains are relatively loose and provide a channel for oxygen transmission, and mixed strains produce corrosive metabolites such as sulfides, phosphides, and other acids, which further exacerbate localized corrosion
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