Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.

Microbial ingress and in vitro degradation enhanced by glucose on bioabsorbable Mg-Li-Ca alloy

Biodegradable magnesium alloys are challenging to be implanted in patients with hyperglycemia and diabetes.A hypothesis is suggested that glucose accelerates microbial ingress and in vitro degradation of Mg-Li-Ca implants.Corrosion resistance and mechanical properties was demonstrated using electrochemical,hydrogen evolution and tensile tests.The bacteria from Hank's solution were isolated via 16S rRNA gene analysis.The results revealed that Mg-1Li-1Ca alloy exhibited different responses to Hank's solution with and without glucose.The solution acidity was ascribed to Microbacterium hominis and Enterobacter xiangfangensis,indicating that glucose promoted microbial activity and degradation and deterioration in mechanical property of Mg-1Li-1Ca alloy.

Influence of Marine Aerobic Biofilms on Corrosion of 316L Stainless Steel

The influence of marine aerobic biofilms on the corrosion of 316 L stainless steel(SS) in aerated and deaerated seawater was studied by electrochemical impedance spectroscopy(EIS), potentiodynamic polarisation curves, current-potential curves and scanning electron microscopy with energy-dispersive spectroscopy(SEM-EDS). EIS and SEM-EDS results showed that the aerobic biofilms inhibited 316 L SS corrosion within the test duration. Comparison of results under aerated and deaerated conditions revealed that O2 enhanced the inhibition efficiency of the aerobic biofilms. This result indicated that living cells were necessary for the aerobic biofilms to inhibit the corrosion of 316 L SS. Polarization curves indicated that the biofilms mainly inhibited anode action. Current-potential curves under deaerated conditions showed that electron transfer processes occurred between microorganisms and electrodes. Moreover, 316 L SS as an electron acceptor was protected from corrosion.

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.