| With the continuous acceleration of the social modernization process,our country's demand for metal materials is very strong.But,due to its complex service environment,it is often accompanied by corrosion,which has caused serious harm to safe production.Therefore,the corrosion protection of metal materials has attracted the attention of many researchers.Among many metal materials,Q235 steel is a widely used low-carbon alloy steel.Because of its good ductility and mechanical strength,it is often used in construction,transportation,and mechanical equipment.At present,inorganic coating technologies such as chromium plating and nickel plating are mainly used for corrosion protection of steel materials at home and abroad,but there are obvious limitations.Therefore,it is very necessary to develop some new anti-corrosion technologies for steel materials.In recent years,conductive polymer polypyrrole(PPy)has been gradually used in the research of metal corrosion protection due to its non-toxicity,good stability and redox ability.This paper mainly controls the preparation process of PPy to study its influence on the anti-corrosion ability of Q235 steel.The main work is as follows:(1)By methods of Electrochemical galvanostatic deposition,PPy films were electropolymerized on Q235 steel surface by adjusting the concentration(0.02?0.18 M)of dodecylbenzene sulfonic acid(DBSA).SEM analysis showed that the PPy films prepared at different doping concentrations all presented the classic"cauliflower"morphology.The sample D-PPy-4 prepared at the doping concentration of 0.14 M had a relatively dense film and a small cluster particle gap.The results of electrochemical tests showed that the sample D-PPy-4 had good corrosion resistance;On this basis,further adjusting the deposition current density(3.0?9.0 m A/cm2)to prepare the PPy films.The PPy film prepared when the deposition current densities was 7.0 m A/cm2,the shape of the cluster particles was relatively complete and smooth.The results of electrochemical tests showed that the sample exhibited good corrosion resistance.When the DBSA concentration was 0.14 M and the deposition current density was 7.0 m A/cm2,the prepared PPy film had the smallest corrosion rate:0.083 mm/y.Compared with Q235 steel(1.64 mm/y),the corrosion rate was reduced by about 20 times.(2)Based on the determination of dopant concentration and deposition current density,PPy films were prepared on Q235 steel with 0.14 m DBSA,0.1 M pyrrole(Py)and different concentrations of sodium molybdate(0.01,0.05,0.10 M)as electrolyte.When the concentration of sodium molybdate was 0.05 M,the PPy film cluster particles of Mo-PPy-2were uniform,regular and compact,and the size of the PPy cluster particles was relatively small.Through the calculation of porosity formula,the sample had the minimum porosity,which was 3.32×10-4.The results of electrochemical tests showed that the corrosion potential of the series of samples were significantly higher than that of Q235 steel(-0.835 V),which were more than-0.2 V.Mo-PPy-2 had the smallest corrosion current densities:3.22?A/cm2,and its corrosion rate was 0.037 mm/y.Compared with Q235 steel,the corrosion rate was reduced by about 44 times,which showed good corrosion resistance for Q235 steel.(3)By method of mechanical coating,single-layer EP/Q235,PU/Q235 and double-layer EP/Mo-PPy/Q235,PU/Mo-PPy/Q235 samples were prepared on the surface of Q235 steel and PPy/Q235.Through electrochemical testing,it was found that the corrosion resistance of double-layer EP/Mo-PPy/Q235 and PU/Mo-PPy/Q235 was better than that of single-layer EP/Q235 and PU/Q235,respectively.Among them,it was found that the corrosion resistance of the single-layer EP/Q235 sample was better than that of the PU/Q235.The double-layer EP/Mo-PPy/Q235 sample still had a relatively small corrosion rate:0.205mm/y after being immersed for 20 days.The salt spray corrosion experiment analysis showed that the corrosion pit depth of the sample EP/Mo-PPy/Q235 was 47.48?m minimum,which showed good corrosion resistance. |
PDF Full Text Request