| Conductive corrosion resistant coatings play an important role in the safety protection of petrochemical equipment and power facilities,which can reduce the occurrence of catastrophic accidents caused by corrosion and charge accumulation and avoid serious economic losses.At present,the conductive and corrosion-resistant coatings are mainly composed of composite coatings with conductive medium added in polymer coatings,and the preparation methods are mainly powder electrostatic spraying and manual painting of liquid coatings.Among them,the coating prepared by the first method has large porosity,poor corrosion resistance and bonding strength,and short service life.The coating prepared by the second method is prone to the settlement of the second-phase conductive medium,and the coating uniformity is poor,which seriously affects the conductivity of the composite coating.In view of the above practical problems,in this study,liquid epoxy resin was used as the film-forming material,and multi-walled carbon nanotubes(MWCNTs)were used as the conductive medium to prepare conductive and corrosion resistant coatings by liquid electrostatic spraying.This method not only gives full play to the excellent adhesion and corrosion resistance of liquid epoxy resin,but also improves the conductivity of the coating by using the directional arrang'ement of the conductive medium MWCNTs in the electrostatic field.The prepared coating is superior to the coating prepared by powder electrostatic spraying and manual liquid phase coating.Firstly,the performance of liquid-phase electrostatic spraying coating,traditional powder electrostatic spraying coating and manual coating was compared.On this basis,the effects of MWCNTs content on the conductivity,corrosion resistance,bonding strength,surface hardness,gloss,friction and wear properties and thermal stability of MWCNTs/epoxy conductive corrosion resistant coatings prepared by liquid phase electrostatic spraying were discussed.The following research results are obtained:(1)The MWCNTs/epoxy conductive and corrosion resistant coating prepared by liquid phase electrostatic spraying can make MWCNTs uniformly distributed by electrostatic force,resulting in better performance of the prepared coating than the MWCNTs/epoxy conductive and corrosion resistant coating prepared by powder electrostatic spraying and liquid phase brushing.When the content of MWCNTs is 0.5wt%,the volume resistivity of the coating prepared by liquid phase electrostatic spraying is 4360?·m,which is about 1/8 of that prepared by liquid phase coating.When the content of MWCNTs is 0.5wt%?2wt%,the conductive network of MWCNTs in the coating is formed quickly,which makes the resistivity of the coating decrease rapidly and the conductivity increase rapidly.When the content of MWCNTs increases to 2wt%,the agglomeration of MWCNTs occurs,and the decrease of MWCNTs in the coating leads to the increase of the resistivity and the decrease of the conductivity of the coating.The curing rate of conductive coating prepared by powder electrostatic spraying is fast,and the conductivity of the coating decreases with the increase of MWCNTs content.(2)The same content of MWCNTs/epoxy conductive and corrosion resistant coatings were prepared by liquid phase electrostatic spraying,powder electrostatic spraying and liquid phase brushing.The coating prepared by liquid phase electrostatic spraying was basically perpendicular to the thickness direction of the coating due to the electrostatic field.The epoxy resin content between the substrate and the coating was higher,resulting in the highest bonding strength of the coating prepared by this method.The conductive medium MWCNTs in the coating prepared by brushing method are disorderly,cross-wound and exist carbon nanotubes.(3)After MWCNTs/epoxy composite conductive corrosion resistant coating and pure epoxy coating were immersed in 3.5 wt%NaCl solution,the polarization curves and AC impedance diagrams of the coatings were similar,which belonged to the corrosion system controlled by the diffusion rate of NaCl solution.The MWCNTs/epoxy conductive and corrosion resistant coating prepared by liquid phase electrostatic spraying has a decrease in gloss due to the shrinkage of epoxy resin and non-shrinkage of MWCNTs during coating curing.However,due to the strength of MWCNTs is higher than that of epoxy resin,the strength of MWCNTs/epoxy resin conductive corrosion resistant coating is higher than that of pure epoxy resin coating,and the carbon in carbon nanotubes can play a lubrication role in friction and wear,resulting in the MWCNTs/epoxy resin conductive corrosion resistant coating prepared by this method.With the increase of MWCNTs content,the wear resistance is gradually enhanced,and the heat resistance of the coating is also improved.(4)The MWCNTs content of MWCNTs/epoxy conductive corrosion resistant coating prepared by liquid phase electrostatic spraying was the best with 2 wt%MWCNTs.At this time,the resistivity of the coating was 128 ?·m.The corrosion rate of the coating immersed in 3.5 wt%NaCl solution at 50? for 30 days was 0.01077 mm/a,and the bonding strength of the coating was 21.81 MPa.The average friction coefficient of the coating was 0.411 measured on HT-100 high temperature friction and wear tester. |
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