Fabrication of anodized superhydrophobic 5083 aluminum alloy surface for marine anti-corrosion and anti-biofouling

Marine corrosion and biofouling seriously affect the service life of marine structural materials,resulting in performance failure,enormous economic loss,and even catastrophic safety accidents.It is worthwhile and desirable to develop high-efficiency strategy for anti-corrosion and anti-biofouling.In this paper,superhydrophobic 5083 aluminum alloy(AA5083)surface with micro-nano hierarchical morphology was fabricated through anodization followed by 1H,1H,2H,2H-perfluorooctyltriethoxysilane(POTS)modification.The surface morphologies,roughness,and chemical compositions were revealed by scanning electron microscopy,atomic force microscopy,and X-ray diffraction.The self-cleaning ability,corrosion resistance and algae adhesion suppression ability of the fabricated surfaces were investigated,indicating an excellent water-proofing,anti-corrosion and anti-biofouling performance.We believe the superhydrophobic creation of metallic materials is expected to have potential applications in marine corrosion and antibiofouling fields.

Analysis of cultivable aerobic bacterial community composition and screening for facultative sulfate-reducing bacteria in marine corrosive steel

Anaerobic, aerobic, and facultative bacteria are all present in corrosive environments. However, as previous studies to address corrosion in the marine environment have largely focused on anaerobic bacteria, limited attention has been paid to the composition and function of aerobic and facultative bacteria in this process. For analysis in this study, ten samples were collected from rust layers on steel plates that had been immersed in seawater for diff erent periods (i.e., six months and eight years) at Sanya and Xiamen, China. The cultivable aerobic bacterial community structure as well as the number of sulfate-reducing bacteria (SRB) were analyzed in both cases, while the proportion of facultative SRB among the isolated aerobic bacteria in each sample was also evaluated using a novel approach. Bacterial abundance results show that the proportions are related to sea location and immersion time;abundances of culturable aerobic bacteria (CAB) and SRB from Sanya were greater in most corrosion samples than those from Xiamen, and abundances of both bacterial groups were greater in samples immersed for six months than for eight years. A total of 213 isolates were obtained from all samples in terms of CAB community composition, and a phylogenetic analysis revealed that the taxa comprised four phyla and 31 genera. Bacterial species composition is related to marine location;the results show that Firmicutes and Proteobacteria were the dominant phyla, accounting for 98.13% of the total, while Bacillus and Vibrio were the dominant genera, accounting for 53.06% of the total. An additional sixfacultative SRB strains were also screened from the isolates obtained and were found to encompass the genus Vibrio (four strains), Staphylococcus (one strain), and Photobacterium (one strain). It is noteworthy that mentions of Photobacterium species have so far been absent from the literature, both in terms of its membership of the SRB group and its relationship to corrosion.

Infl uence of nitrate concentrations on EH40 steel corrosion aff ected by coexistence of Desulfovibrio desulfuricans and Pseudomonas aeruginosa bacteria

Nitrate addition is a common bio-competitive exclusion(BCE)method to mitigate corrosion in produced water reinjection systems,which can aff ect microbial community compositions,especially nitrate and sulfate reducing bacteria,but its eff ectiveness is in controversy.We investigated the infl uence of nitrate concentrations on EH40 steel corrosion aff ected by coexistence of Desulfovibrio vulgaris and Pseudomonas aeruginosa bacteria.Results demonstrate that only mixed bacteria or nitrate had little eff ect on EH40 steel corrosion,and nitrate could accelerate the corrosion of EH40 steel through the action of microorganisms.The corrosion promotion of nitrate was dependent on its concentrations,which increased from 0 to 5 g/L and decreased from 5 to 50 g/L.These diff erences were believed to be related to the regulation of nitrate in the growth of bacteria and biofi lms.Therefore,care must be taken to BCE method with nitrate when nitrate reducing bacteria with high corrosive activity are present in the environments.

Inhibition of Zinc Corrosion by Fucoidan in Natural Sea water

Research on corrosion behaviour of zinc in natural sea water without and with fucoidan was carried out by potentiodynamic polarisation test and electrochemical impedance spectroscopy （EIS）. The results revealed that fucoidan serves as a good inhibitor for zinc in sea water. Polarisation curves suggested that corrosion potential values shifted to the positive ones after adding inhibitor and fucoidan retards anodic reaction more. Thus, fucoidan can be acted as anodic inhibitor. EIS results showed two phenomena including a charge transfer and an adsorption film. The corrosion inhibition of fucoidan was further confirmed by the scanning electron microscope （SEM） and atomic force microscope （AFM） analysis. Langmuir＇s adsorption isotherm was found the appropriate adsorption model.