Preparation Of Two-dimensional Nanosheet/Conductive Polymer Organic Composite Coatings And Study Of Corrosion Protection Properties

Organic coatings are one of the most effective protection strategies against corrosion,however,during the evaporation of solvents a large number of micropores remain inside the coating,the presence of these micropores makes it easy for external media to penetrate into the metal matrix,thus reducing the corrosion resistance.In recent years,two-dimensional nanomaterials with a unique lamellar structure have excellent physical barrier properties,which can both prevent the penetration of corrosive media and fill micro-pores,pinholes and other defects in organic coatings.In addition,to enhance corrosion resistance,the addition of conductive polymers to the coating is also a common and effective method.Combining physical and electrochemical corrosion protection mechanisms,this paper prepared coatings with excellent corrosion resistance by intercalating conductive polymers with two-dimensional nanosheets and then adding them to an organic matrix.The main elements are as follows:（1）The MXene@PANI complex was made by intercalation reaction between PANI and two-dimensional Ti₃C₂T_x,and then MXene@PANI was added to polyurethane（PU）matrix to obtain MXene@PANI/PU protective coating.The results showed that the MXene@PANI 1:1 coating had the highest adhesion and hardness of 5.9 MPa and 76 HA,respectively,and the highest tensile strength at break of 3.43 MPa.The surface of the MXene@PANI 1:1 coating showed no obvious corrosion after 60 days of immersion in 3.5 wt%NaCl solution,the corrosion potential of was-0.594 V,the corrosion current density was 3.709×10^-9 A·cm^-2 and an impedance modulus value of 1.93×10⁸Ω·cm^-2,both better than pure PU(-0.729 V,5.263×10^-6 A·cm^-2,6.07×10³Ω·cm^-2).The improved corrosion resistance is attributed to two factors:MXene improves the electrochemical activity of PANI and enhances its electrochemical corrosion protection;Ti₃C₂T_xnanosheets can act as a two-dimensional barrier to inhibit corrosive media from entering the interior of the coating,improving its long-lasting protection performance.（2）The TA@LDH complex was made by intercalation reaction between TA and LDH nanosheets,and then TA@LDH was added into PU matrix to obtain TA@LDH/PU protective coating.The results showed that the addition of TA@LDH improved the mechanical properties of PU,and the adhesion of TA@LDH/PU coating was up to grade 0,and the hardness was 6 H;the tensile strength was 0.6 MPa.After immersing in 3.5 wt%NaCl solution for 72 h,the corrosion potential of TA@LDH/PU coating was-0.594 V,the corrosion current was 2.273×10^-7A·cm^-2 and impedance modulus value of 3.56×10⁷Ω·cm^-2;this work showed that the conditioning of PU matrix by reasonable doping of TA@LDH was an effective means to improve the anticorrosion performance of the material.（3）The PPy@LDH composite was prepared by intercalation reaction of PPy and LDH nanosheets,and then PPy@LDH was added to epoxy resin（EP）matrix to obtain PPy@LDH/EP protective coating.The results showed that the addition of PPy@LDH improved the mechanical properties of EP.The highest adhesion of PPy@LDH/EP coating was 0 grade and the hardness was 6 H.The tensile strength of PPy@LDH 1:6 was 87 MPa.After immersed in 3.5 wt%NaCl solution for 72 h,the corrosion potential of PPy@LDH/EP coating was-0.376 V,the corrosion current was 5.834×10^-9 A·cm^-2,and the impedance modulus was 5.67×10⁶Ω·cm^-2,which were better than pure EP(-0.793 V,9.471×10^-6 A·cm^-2,3.51×10³Ω·cm²).This work showed that adjusting the EP matrix by reasonably doping PPy@LDH was an effective means to improve the corrosion resistance of the material.