Study On The Corrosion Protection Of Graphene Composite Coatings On The Surface Of Aluminum

Aluminum and its alloys are widely used in construction,packaging,military industry and new energy fields due to their advantages such as small specific gravity,easy processing and excellent thermal conductivity.Aluminum surface is easy to generate a layer of oxidation protection film to improve the corrosion resistance,but in medium such as neutral salt,the stability of the oxide film decreases significantly,which may induce serious corrosion of aluminum substrate,so it is not only necessary but also urgent to develop more effective corrosion protection measures.Graphene has a broad potential application prospect in the field of metal corrosion protection,due to its excellent shielding,corrosion inhibition and hardening properties.This work focused on the composite coating of graphene as a nano-filler doped in modified polyurethane organic coating and chitosan quaternary ammonium salt.The electrochemical test method was used to investigate the effect of graphene on the corrosion resistance of the coating,and the corrosion resistance mechanism was discussed.The main research progress of this thesis is as follows:(1)Scanning electron microscope(SEM)?Infrared reflection absorption spectrum?X-ray diffraction spectrum?Raman spectrum?Thermogra vime and X-Tay photoelectron spectroscopy were used to characterize the graphene synthetic materials.It was found that the graphite was oxidized to graphite oxide by the impoved Hummers method,the structural surface of the products were modified with a large number of oxygen-containing functional groups,which was then reduced to graphene by the strong base heating method.(2)Electrochemical research methods,SEM,thermal conductivity analyzer,drawing experiment and hundred lattice analysis were used to study the influence ofmodified polyurethane composite coating doped with different content of graphene on the corrosion behavior of aluminum in 3.5%NaCl solution as well as its influence on thermal conductivity and binding force.The results showed that a small amount of graphene added would significantly improve the corrosion protection performance,however,excessive graphene did not increase or even decreased the corrosion resistance,this was mainly associated with the dispersion state of graphene,when the graphene doping amount was 0.025 wt%,corrosion protective performance of the composite coating was the best;the thermal diffusivity of the insulating organic coating was increased by more than 40 times with the increase of graphene mass fraction;graphene could increase the adhesion between the coating and the aluminum surface,but only by a limited amount.(3)Electrochemical technology,atomic force microscopy and SEM were employed to study the effects of graphene on the corrosion resistance of chitosan quaternary ammonium salt film electrochemically deposited on the surface of aluminum and the compatibility of composite film with modified polyurethane coating,and the anticorrosion mechanism of graphene composite film was discussed.The results showed that the chitosan quaternary ammonium salt composite film had the strongest corrosion resistance and good compatibility with the organic coating when deposited for 1200 s.The anticorrosive mechanism of graphene in coatings could be considered to be mainly based on the filling and shielding effect.