[Introduction]Environmentally friendly pretreatment processes with excellent performance are required for painting carbon steels.[Method]Q235 carbon steel was pretreated by silanization,zirconization,and silanization-zirconization composite processes,respectively.The properties of the pretreatment films were examined through neutral salt spray(NSS)test,electrochemical measurement,pull-off adhesion test,and micromorphology analysis.[Result]All of the pretreatment processes improved the corrosion resistance of the substrate.The surface of the untreated Q235 carbon steel was seriously corroded after 2-hour NSS test,and the corrosion area of the specimen pretreated by the composite process was not more than 10%.The results of electrochemical polarization curve measurement showed that the corrosion potentials of the pretreated specimens were shifted toward the positive direction.The corrosion current density of the specimen pretreated by the silanization-zirconization composite process was only 1/38 of that of the untreated one.The results of electrochemical impedance spectroscopy indicated that the corrosion reaction resistance of the substrate was increased after pretreatment,and the surface roughness of Q235 carbon steel was increased after both zirconization and silanization-zirconization composite pretreatment.The pull-off adhesion strength of the epoxy coatings sprayed on the three types of pretreatment films was higher than 10 MPa,meeting the general coating quality requirement.[Conclusion]All of the three pretreatment processes can improve the corrosion resistance of carbon steel substrates and the adhesion strength of the coatings sprayed on them,in which the silanization-zirconization composite process shows the best performance.
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