Preparation And Anti-corrosion Mechanism Of In₂O₃-based Photoelectronic Nanomaterials Loaded Epoxy Composite Coatings

Photocathodic protection technology is a new type of green anti-corrosion technology that uses photovoltaic effect of semiconductor to provide cathodic protection for metals.However,it relies too much on solar radiation and cannot be used in rainy days or at night,which greatly limits its application in practical engineering.In order to solve this problem,epoxy coatings loaded with In₂O₃-based photoelectric nanomaterials were prepared in this paper.The photocathodic protection performance of In₂O₃-based photoelectric nanomaterials was studied,and the influence of In₂O₃-based photoelectric material load on the density,hydrophilicity and mechanical strength of epoxy coatings was explored.The anti-corrosion mechanism of In₂O₃-based photoelectric nanomaterials loaded epoxy composite coating was revealed.The main research contents are as follows:（1）In₂O₃ nano-films were prepared on FTO conductive glass by hydrothermal method,and then In₂O₃/CeO₂ and In₂O₃/C₃N₄ composite photoanode materials were prepared by secondary hydrothermal method and spin coating method respectively.The composition and morphology of the photoanode were characterized by XRD,SEM and HRTEM.The optical properties of In₂O₃ were characterized by UV-vis DRS and PL.It was found that the optical absorption range of In₂O₃ was expanded from 380nm to 450nm and 500nm by the modification of CeO₂ and C₃N₄,and the photoelectron-hole recombination rate was significantly reduced.In₂O₃,In₂O₃/CeO₂ and In₂O₃/C₃N₄photoanodes can all negatively shift the open circuit potential of 304SS,but only In₂O₃/C₃N₄ can significantly negatively shift the potential of Q235CS.The results of photogenerated current density also show that the photogenerated current density of the composite photoanode material increases significantly.Finally,ESR test results show that the charge transfer mechanism of In₂O₃/CeO₂ and In₂O₃/C₃N₄ composite photoanodes is consistent with the traditional type II heterojunction and the new type Z heterojunction,respectively.（2）The pure epoxy and epoxy/In₂O₃/C₃N₄ composite coatings with different In₂O₃/C₃N₄ content were prepared by spraying on the surface of 304SS sheet by mixing In₂O₃/C₃N₄ with epoxy resin.The addition of In₂O₃/C₃N₄can increase the contact Angle and enhance the tensile strength of the coating,and the maximum is 25.26MPa when the dosage of In₂O₃/C₃N₄ is 0.8g.UV aging and salt spray test results show that the addition of In₂O₃/C₃N₄ nanomaterials can effectively improve the anti-UV aging and salt spray properties of epoxy coatings.Under the condition of no light,the electrochemical test of different coating samples with different soaking time showed that the change of open circuit potential and polarization potential of epoxy/In₂O₃/C₃N₄ composite coating was smaller than that of pure epoxy coating,indicating that the addition of In₂O₃/C₃N₄enhanced the corrosion resistance of the coating and made it have better physical barrier properties.（3）The epoxy/In₂O_3/C₃N₄/CNT composite coating was prepared by adding carbon nanotubes（CNT）to enhance the conductivity and photocathodic protection of the coating.The results show that the epoxy/In₂O₃/C₃N₄ and epoxy/In₂O_3/C₃N₄/CNT composite coatings can negatively shift the open circuit potential of 304SS to about-400m V and-500m V,respectively.The addition of CNT can effectively improve the conductivity of the coating and improve the photocathodic protection performance.（5）The anticorrosive mechanism of the epoxy/In₂O₃/C₃N₄/CNT composite coating prepared in this paper is analyzed.It is concluded that the photogenerated electrons generated by the photoexcitation of the In₂O₃/C₃N₄ photoanode material in the coating can migrate to the protected metal when there is light,providing cathodic protection for it.In the absence of light,the addition of In₂O₃/C₃N₄ and carbon nanotubes（CNT）can enhance the density of epoxy,prolong the penetration path of corrosive medium,and improve the physical barrier ability of coating.The photocathodic protection technology and the physical protection of coating cooperate to improve the corrosion resistance of steel structure.