| In the field of marine anticorrosion,epoxy resin is the most widely used high-performance anticorrosive synthetic resin,and it is also the best substitute for chromate with strong toxicity and carcinogenicity.But the cured epoxy resin has the problem of low toughness and poor heat resistance.It is easy to cause stress crack to cause the failure of the coating.And with the increasingly severe condition of marine service,the corrosion resistance of traditional epoxy coatings can not meet the requirements of marine heavy duty（10 years）,which limits the application of epoxy resin in the field of anticorrosion.The purpose of this project is to develop an epoxy anticorrosion coating with high mechanical properties,strong adhesion and long corrosion resistance.On the basis of consulting the literature at home and abroad and preliminary exploration,this paper has determined the research goal,the research scheme and carried out the following research work.（1）Polyurethane（PU）modified epoxy resin（EP）is used to form an interpenetrating polymer network,and the effect of different reaction conditions on the mechanical properties of the polymer is studied systemztically.The results show that the reaction conditions of PU/EP polymer after 5h reaction at 75℃are the best.When PU content is 15%,the tensile strength,elongation at break and impact toughness of PU/EP polymer are increased by 82.92%,106.20%and 26.65%compared with pure EP,which not only demonstrates good toughness and excellent tensile strength,but also has the best comprehensive mechanical properties.（2）In order to determine the best composition of the polyurethane/epoxy resin zinc aluminum composite,different amounts of scaly Zn-Al alloy powders are added to the PU（15%）/EP polymer and the orthogonal test is designed to comprehensive evaluate the appearance,hardness and fast corrosion time of NH4NO3.The optimized composition（mass fraction）of the composite coating is:9%Zn-Al,30%PU/EP,12%D-230,2.25%KH-550,5%OP-10,5%1,4-propylene glycol,10%n-butyl alcohol,35 drops isooctanol and the remaining amount is water.The morphology of the coatings prepared as the optimized composition is a"labyrinth"structure with Zn-Al alloy parallel stacked.The corrosion voltage（-0.912V）is lower than that of the Q235 substrate（-0.641 V）and the PU/EP coating（-0.581 V）,which plays a sacrificial role in cathodic protection.The corrosion current density is 3.580×10-6A·cm-2,which is one order of magnitude lower than that of Q235 substrate and also significantly lower than that of PU/EP coating(7.104×10-6A·cm-2),and the coating with optimized composition coating has the lowest corrosion rate.（3）Nano SiO2 is added to the optimized composition PU/EP zinc aluminum composite coating,the effect of nano SiO2 on the hardness,water absorption and corrosion resistance of nanocomposite coatings is studied.The results show that when the weight fraction of the added nano SiO2 is 7%,the hardness of the nanocomposite coating is increased by 34.34%,the water absorption rate is obviously lower and the corrosion current density(3.733×10-88 A·cm-2)is 3 orders and 2 orders of magnitude lower than that of Q235 and PU/EP zinc aluminum composite coating respectively.The time to maintain corrosion resistance in3.5%NaCl solution increased from 120d to 180d.Thus it can be seen that the 7%SiO2-nanocomposite coating can effectively prolonging the service lifetime of marine engineering equipment in the field of heavy anticorrosion. |
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