Study Of Microbial Corrosion Behaviour Of Coiled Tebing

Due to the complexity of Marine environment,Marine engineering equipment and facilities are inevitably threatened by corrosion of seawater and Marine organisms during service.The early adhesion of microorganisms and the formation of biological films are the key factors to induce marine microbiologically influenced corrosion.Therefore,it is of great significance to develop new antibacterial materials and coatings with high efficiency and environmental protection.In this thesis,molybdenum trioxide and molybdenum trioxide and zirconium molybdate composite materials were prepared by one-step thermal decomposition method and sol-gel method respectively.The microstructure,phase structure,chemical functional groups and optical properties of the prepared materials were characterized.Antibacterial tests were carried out with Pseudomonas aeruginosa,widely existing in Marine environment as corrosive bacteria.The antibacterial properties and action mechanism of the materials were studied in dark and light conditions.Molybdenum trioxide antibacterial material was dispersed in epoxy resin to prepare antibacterial coating on Q235 steel.The mechanical properties,antibacterial properties and anti-corrosion properties of coating were studied.The research results are as follows:（1）Nano-plate and micron scale plate-like α-MoO₃ samples,namely S450 and S750,were prepared by one-step thermal decomposition at 450℃ and 750℃,respectively.Both S450 and S750 have good antibacterial properties under light and dark,and the antibacterial rate of S450 is obviously higher than that of S750,and the antibacterial rate under light condition is higher than that under no light condition.Compared with S750,S450 dissolves and produces more H3O+and Mo ions.And the higher the concentration of H3O+and Mo ions,the higher the antibacterial rate.In addition,reactive oxygen species（ROS）including·OH,·O2and 1O2 were not produced in S450 and S750 under no light condition,but·OH,·O2-and 1O2 were produced after exposure to light.Therefore,ROS production is the main reason for the increase of antibacterial rate under light condition.（2）The sol-gel method was used to synthesize MoO₃/ZrMo₂O₈ composite material.MoO₃ was long plate and ZrMo₂O₈ showed irregular block.MoO₃/ZrMo₂O₈ composite widened the visible light absorption range of the composite material,improve its absorption capacity of sunlight.MoO₃/ZrMo₂O₈ composites showed antibacterial activity under both light and dark conditions,and the antibacterial rate under light condition was higher than that under dark condition.（3）The coatings with o,0.5%,1%,2.5%and 5%α-MoO₃ at nanoscaled size and excellent antibacterial properties in epoxy resin were prepared.The results showed that MoO₃ was uniformly distributed in the coating and the coating thickness was about 24 μm.The adhesion between the coating and the substrate was at level 0,indicating good interface bonding.The antibacterial properties of the coating were evaluated by plate count method and bacterial fluorescent staining assay.The results showed that the antibacterial rate of the coating was increased with the increase of MoO₃ concentration.The antibacterial rate was also increased to 80%for 1%MoO₃ coating after light exposur.The electrochemical corrosion test in 3.5%NaCl,sterile 2216E and bacterial 2216E showed that the corrosion resistance of the coating increased first and then decreased with the increase of MoO₃ concentration,and the corrosion resistance was 1%>0.5%>2.5%>5%>EP.The 1%MoO₃ coatings showed the best corrosion resistance,indicating that the addition of α-MoO₃,Its impedance modulus values in 3.5%NaCl,sterile 2216E and bacterial 2216E were 3.77× 106,8.56×105 and 2.65×105 Q/cm2,respectively,and the corrosion current density was 1.68×l0-9,1.02×10-8 and 1.22×10-8A/cm 2,respectively.increased the corrosion resistance of the coatings in the environments with or without bacteria.