Fabrication Of Super-hydrophobic Coating On Copper And Its Corrosion Behavior

Copper has a series of advantages such as excellent electrical conductivity,high thermal conductivity and good ductility.But copper has poor corrosion resistance under the environment which is humid or contains corrosive medium.Finding an efficient and practical method to improve the anti-corrosion property has great significance to copper's application.In order to improve the anti-corrosion property of cooper,this article respectively fabricated PDMS/diatomaceous earth?DE?coating and PDMS/DE/SiO₂ coating on copper by dip-coating.By studying the mass ratio of PDMS and DE and the number of dip-coating times during the preparation process,the influencing rules of surface morphology,phase composition,wettability and corrosion resistance of PDMS/ DE coating were studied.And the main factors which affect the corrosion resistance of the coating were analyzed,at the same time,the corrosion resistance mechanism of the superhydrophobic coating was illuminated.In addition,in order to modify the rough structure of the coating surface,nano-silica particles of different qualities were added to the solution,and the influence of nano-silica content on the morphology,wettability and corrosion resistance of the superhydrophobic coating was studied.The evolution rules of the impedance spectrum of the coating during immersion in NaCl solution has also been researched.The results indicate that the combination of DE with natural micro-nano hierarchical structure and PDMS with low surface energy makes the coating superhydrophobic.In the process of coating preparation,the mass ratio of PDMS and DE and the number of dip-coating times have significant influences on the coating's exposure area and thickness,thus changing the wettability and corrosion resistance of the coating.When DE particles cover the coating surface completely,the contact angle of the coating is 150°?155°.The addition of nano silicon dioxide modifies the microstructure of the coating,so that the contact angle of the coating is significantly improved.After 0.3g of nano silicon dioxide is added to the solution,the contact angle of the coating reaches 167°,indicating that the coating has excellent superhydrophobic performance.The polarization curve and electrochemical impedance spectroscopy show that the coating improves the corrosion resistance of copper notably.Wettability and the thickness of coating are the important factors which affect the coating's anti-corrosion property.With the increase of DE content and the number of dip-coating times,the corrosion resistance of the coating improves,obviously,the corrosion current density decreases and passivation area increases in the polarization curve of the coating.When the mass ratio of PDMS and DE is 1:2 and dip-coating times is 3,the corrosion current density of the coating is just 5.16 x 10-9 A/cm²,which decreases about 3 orders of magnitude as compared to that of bare Cu?3.64 x 10-6 A/cm²?,at the same time,the protective efficiency of the coating was 99.86%,so the coating shows excellent corrosion resistance.When the coating is immersed in NaCl solution,the micro-nano structure on the coating surface can capture the air to form an air layer at the initial stage of immersion,thus effectively preventing the penetration of solution to the substrate.At this time,the coating has a high impedance value.With the increase of immersion time,the air layer disappears and the solution penetrates into the coating,which shows the decrease of impedance value and the emergence of new time constant at low frequency in the impedance spectrum.But for the thicker coating,the higher impedance can be maintained in the longer immersion time,so that the coating shows good corrosion resistance.In addition,coatings containing nano SiO₂ particles exhibit better corrosion resistance due to their excellent superhydrophobic properties.