Study On Application Of Graphene Coating In Oil Tank Corrosion Protection

Oil storage tank is the leading equipment for storing and transferring petrochemical products,which is widely used in petrochemical industry and oil depot enterprises.With the deterioration of domestic crude oil quality and the increase of import crude oil and oil transportation volume,the corrosion problem of crude oil storage tanks has become increasingly prominent.In the process of oil exploitation,water and corrosive medium are often mixed.In the long term storage process,"water is floating and oil is floating",corrosive sedimentary water is accumulated at the bottom of the tank,so that the bottom of the tank is immersed in sedimentary water for a long time.The composition of the accumulated water is complex,containing a large number of chloride ions,sulfates and anaerobic microorganisms.These media make the bottom of the tank bottom in a strong corrosive environment and cause continuous corrosion to the bottom of the tank.In order to better carry out the tank anti-corrosion work for the corrosive medium heavy water,corrosion behavior of steel in different sedimentary water,combined with the corrosion mechanism,corrosion protection technology of floor coating tank is studied.Specific as follows:The electrochemical corrosion behaviors of Q235,X65,X80 and 316L steels in oil tank sediment water was studied using electrochemical impedance spectroscopy?EIS?and Potentiodynamic polarization results polarization curves.The corrosion morphology and corrosion products of steel were analyzed by scanning electron microscopy?SEM?,electron spectroscopy?EDS?and X-ray diffraction?XRD?.Results indicated that some loose corrosion products were generated on the Q235,X65 and X80 steels surface after 24 days immersion.However,little corrosion was occurred on the 316L;Polarization curves show that corrosion current density of Q235 steel(3.462?A?cm^-2),X65 steel(4.122?A?cm^-2)and X80 steel(5.848?A?cm^-2)were much higher than 316L steel(0.118?A?cm^-2)in sediment water,Passive zone could be observed obviously on the polarization curves of 316L steel.The electrochemical impedance spectroscopy indicated that impedance modulus of Q235,X65 and X80 steels increased slowly with immersion time,and then decreased.However,there was no significant change in the impedance modulus of 316L steel.The corrosion of steel in sedimentary water is not only related to mineral ions,but also to the compactness of scale film formed by mineral ions.Based on the above experiments,graphene was used as the filler and was chemically dispersed into aqueous solution.The dispersion and number of layers of graphene were characterized by TEM and AFM.The dispersed graphene was added to two-component waterborne epoxy resin to prepare graphene epoxy composite coating.The water resistance and corrosion resistance of composite coatings in simulated seawater solution were investigated by coating water absorption,polarization curves and AC impedance spectroscopy.The result shows that:compared to the pure epoxy coating,polarization resistance and corrosion resistance of composite coatings is obviously improved,graphene have good water resistance,can improve the coating resistance and charge transfer resistance,enhance the protective performance of waterborne epoxy coating.At last the water deposited for actual crude oil tank corrosion medium,using self-made graphene primer and topcoat for protective coating system,spectroscopy,potentiodynamic polarization curves by AC impedance,corrosion behavior of graphene coating system in sedimentary water with salt spray test and failure evolution mechanism.The results showed that graphene primer has a protective effect on carbon steel in the early stage of immersion,with the extension of soaking time,water molecules gradually penetrate into the coating,coating gradually failure;antiseptic effect of anti-corrosion layer of primer primer and finish collocation is significantly difference with the immersion time test the corrosion current density and salt fog the experiment shows that,using graphene and graphene primer coat collocation,can significantly improve the performance of protective coating for carbon steel in sedimentary water,after 46 days of immersion,the coating resistance is 162 M?cm.It can achieve good protection effect,and can greatly improve the anti-corrosion effect of coating on the bottom of oil tank.