Fabrication And Protection Mechanism Of Anti-corrosion Bionic And Elastic Functionally Gradient Surface

Marine environment is a complex corrosive environment.Chemical,physical and biological factors have effects on metal corrosion,and these effects are interrelated.Marine equipment has been working in the marine environment for a long time.Corrosion and wear will inevitably occur to the related motion systems.Coating protection for marine equipment is an economical and effective way of protection.Inspired by the elastic erosion resistance of dolphin skin and gradient structure of bamboo tube wall section,a new anti-corrosion bionic and elastic functionally gradient surface was designed and prepared in order to protect marine equipment.The three gradient layers of the anti-corrosion bionic and elastic functionally gradient surface are erosion resistant surface layer,elastic buffer layer and basement connection layer from outside to inside.Based on the principle of bionic similarity,the design and erosion resistance of bionic functional surfaces with different gradient layers and elastic gradient structures on functional surfaces were carried out using polyurethane(PU)and two-component room temperature vulcanized silicone rubber(RTV-2)as main materials.Polyurethane/silicone rubber composites with interpenetrating polymer network(IPN)structure were prepared by mechanical blending method,and the mass fraction of the composites was optimized based on the study of mechanical properties,erosion resistance and corrosion resistance as well as the bonding properties with metal materials.According to GB/T 7757,GB/T 528,GB/T 12830,GB/T 10834 and other standards,the mechanical properties of PU,RTV-2 and their composites with mass fractions of 75% PU+25% RTV-2,50% PU+50% RTV-2 and 25% PU+75% RTV-2 were tested by rubber electronic tensile testing machine.The erosion and corrosion resistance of the composites was investigated by self-made erosion testing machine.The experimental results show that PU has good mechanical properties such as tensile and shear resistance,and the bonding effect with metal is the best,but its modulus of elasticity is higher.With the addition of RTV-2,the modulus of elasticity of the composites begins to decrease,but the mechanical properties of the composites also decrease.Static seawater corrosion test and dynamic erosion test show that PU has higher water absorption and better erosion resistance.With the addition of RTV-2,the hydrolysis resistance of the composites tends to improve,but the erosion weight loss rate also gradually increases.The results show that the composites prepared by 75% PU + 25% RTV-2 mass fraction show better comprehensive properties and are most suitable as the buffer intermediate layer of the bionic elastic gradient functional surface.According to different purposes,three kinds of gradient elastic biomimetic functional surfaces with different structures were prepared by using PU,RTV-2 and 75% PU+25% RTV-2 mass fraction composites,which were prepared by layer-by-layer coating and whole pressing vulcanization.The mechanical properties,erosion resistance and corrosion resistance of the above surface were tested and characterized by electron microscopy.The results show that PU is the surface material,75% PU + 25% RTV-2 is the buffer intermediate layer,PU or RTV-2 is the bionic functional surface 3 and 2 of the base connection layer.Compared with single PU material,the bionic functional surface 3 and 2 show better erosion resistance.Functional surfaces have better erosion and corrosion resistance than single-layer materials.The bionic elastic gradient functional surfaces have obvious gradient stratification structure by integral pressing and vulcanization,and the bonding of different gradient layers is close and no separation occurs under 1000 times electron microscopy.The anti-corrosion mechanism of the bionic gradient functional surface is theoretically analyzed based on the mechanism of erosion and corrosion.The anti-corrosion mechanism of the functional surface is mainly related to the anti-erosion and wear ability of the anti-erosion surface layer and the overall compliance to the fluid.According to the typical theory of fluid erosion,the functional surface can effectively achieve the compliance to the fluid.The effect of barrier fluid and solid particles directly scouring metal matrix and absorbing impact energy.The performances of PU,RTV-2,PU/RTV-2 composites and three kinds of anti-corrosion bionic functionally gradient elastic surfaces were compared comprehensively.It was found that the functional surface 3 had good mechanical properties,erosion resistance and corrosion resistance,as well as bonding ability with metals.It was the most practical application value of the preparation scheme of the bionic anti-corrosion functionally gradient elastic surface,which was compared with the traditional coating.It combines the mechanical properties,the energy absorption and the cohesion ability with the marine equipment.To a certain extent,it also has the ability to prevent cavitation corrosion.The smooth surface of the anti-erosion surface also has the function of preventing the attachment of marine organisms.