Preparation Of Polypyrrole And Its Application In Corrosion Protection Of Q235 Steel

Nowadays,with the rapid development of the economy,steel materials are one of the indispensable metal materials in various industrial fields.Among them,Q235 steel is an important structural engineering steel,which is widely used in the manufacture of steel bars,construction of factory buildings and high-voltage transmission towers,and it is also widely used in bridges,vehicles and ships.However,as it is often used in aggressive environments such as moisture and seawater,its corrosion failure behavior has received much attention.The conductive polymer polypyrrole?PPy?is gradually applied to the field of metal corrosion protection due to its non-toxicity,strong stability and good redox ability.The main research contents of this paper are the application of PPy products prepared by different methods in the field of corrosion protection of Q235 steel.The main work is as follows:?1?PPy films were prepared on the surface of Q235 electrode by electrochemical potentiostatic method at a deposition potential of 0.7,0.8,0.9,1.0 and 1.1 V respectively,in an aqueous solution containing sodium dodecylbenzenesulfonate?SDBS?as a dopant.SEM and FT-IR analysis showed that the dense film formed by the accumulation of PPy particles doped with SDBS could be successfully prepared on the surface of Q235 electrode in the potential range of 0.7¹.1 V,and it found that the deposition potential directly affected the particle size of the PPy product;electrochemical Tafel and EIS test results showed that the PPy-Q235 sample prepared at a deposition potential of 0.8 V has the best corrosion resistance.On this basis,PPy-Q235 samples were prepared by potentiostatic method at a concentration of pyrrole monomer of 0.05,0.10,0.15 and 0.20 M,respectively.SEM and FT-IR analysis showed that the pyrrole monomer concentration directly affected the particle size of the PPy product and the density of the film,and the particle size of PPy prepared with the pyrrole monomer concentration of 0.10 M is the smallest;the results of electrochemical test showed that the PPy-Q235-0.10 samples exhibited superior corrosion resistance due to its smaller porosity.?2?At first,KH560 silane film was prepared on the surface of Q235 electrode by dip coating method.SEM and FT-IR analysis confirmed that a uniform KH560 silane film was formed on the surface of Q235 electrode;the water contact angle and adhesion test showed that the water contact angle of the KH560-Q235 sample was 84.7°and the adhesion was 11.22 MPa;the electrochemical test results showed that the KH560 silane film has good corrosion protection ability to the Q235 substrate.Then,on the surface of the silane film,the PPy film was deposited by potentiostatic method.SEM and FT-IR analysis showed that the PPy film was successfully prepared on the surface of the KH560-Q235 sample;the water contact angle and adhesion test showed that the PPy-KH560-Q235 sample has better hydrophobicity and adhesion than the PPy-Q235 sample;electrochemical tests showed that the corrosion resistance of the PPy-KH560-Q235 sample was greatly improved,which was mainly attributed to the introduction of KH560 interlayer film to improve the adhesion and hydrophobicity of the film,which can effectively hinder the corrosion of corrosion ions in the electrolyte;the immersion corrosion test showed that the corrosion protection of PPy-KH560-Q235 sample decreased greatly after 240 h of immersion in 3.5 wt.%NaCl solution.?3?The PPy product was prepared by chemical oxidation method with using FeCl₃as oxidant.Different PPy products were obtained by introducing different dopants?SDBS,CTAC,NaPTs?into the synthesis system.SEM and FT-IR results showed that the dopant has a certain influence on the morphology and molecular structure of PPy products.PPy/EP coatings were prepared by blending PPy products with epoxy resin?EP?coatings,and the corrosion resistance of PPy/EP-Q235 sample was investigated.The electrochemical Tafel and EIS test showed that the corrosion resistance of PPy/EP-Q235 samples is significantly improved compared with EP-Q235 samples,and the S-PPy/EP-Q235 sample has the best anti-corrosion effect;the salt spray corrosion test results show that after 20 days of salt spray corrosion,pitting pits with different degrees of corrosion appear on the surface of the sample,among them,the average depth of pitting pits on the surface of Q235 electrode covered by S-PPy/EP coating is the smallest;the results of the immersion corrosion test showed that the coatings are destroyed after 20 days of immersion,and the corrosion ions erodes the Q235steel matrix,but the S-PPy/EP-Q235 samples have relatively good corrosion resistance compared to other coating samples.