Study Of Preparation And Properties Of Anti-corrosion Superhydrophobic Coatings On AE44 Magnesium Alloy

In order to solve the corrosion protection problem of AE44magnesium alloy for shock absorber of automobile,superhydrophobic coatings are fabricated after traditional protection layer in the paper.First,MAO technology is selected to prepare bottom layer among the traditional corrosion protection methods.What’s more,PDMS-PVDF-SiO₂ system is preferred to prepare the superhydrophobic coating layer.Faced with the problem that the superhydrophobic membrane layer is not robust enough,this paper proposes two methods.Firstly,to add an interlayer.Secondly,adding PVDF emulsion in the superhydrophobic suspension.The main research results are as follows:（1）The Micro-arc Oxidation coating layer on the surface of the prepared AE44 magnesium alloy is well bonded to the substrate,and the color of the coating layer is gray.The surface of the coating is even and smooth.But there are a large number of obvious holes and a few fine cracks under the microscope.The coating layer is dominated by elemental Mg phase and MgO phase.After micro-arc oxidation treatment,the corrosion current of AE44 magnesium alloy decreased from 2.12×10^-5A·cm^-2 to2.93×10^-6A·cm^-2,one order of magnitude,which improved the corrosion resistance of magnesium alloy substrate to some extent.（2）After the Micro-arc Oxidation coating layer is prepared,the corrosion resistance and bonding force,especially the former,of the subsequent superhydrophobic coating layer can be greatly improved.The self-corrosion current of the original superhydrophobic coating layer drops from 1.24×10^-6A·cm^-2 to 1.58×10^-11A·cm^-2,for 5 magnitude,compared with one without the interface treatment using KH550（γ-aminopropyltriethoxysilane）as silane coupling agent.KH550 performs a certain improvement on bonding to superhydrophobic coating layer,compared with one even can’t withstand the tape peeling test for once before.Peeling cycles improved from 0 times to 2 times.（3）Besides the interface treatment,the PVDF emulsion was added to the original superhydrophobic membrane layer.With content 20 wt.%,the initial contact Angle of the superhydrophobic film is 155°,and the rolling Angle is 2°,and the PDMS-PVDF-SiO₂ superhydrophobic membrane layer had the best bonding force.The bonding strength is greatly improved meanwhile maintaining corrosion resistance(with self-corrosion current1.58×10^-11A·cm^-2).It’s still superhydrophobic after tape peeling for 40times,maintaining contact angle as 151°.In addition,the superhydrophobic coating layer was post-treated:the superhydrophobic solution was appropriately diluted and used as a new solution,and the superhydrophobic coating layer was immersed in the new solution to form a coating.The post-treatment can effectively reduce the crack of the coating while maintaining the superhydrophobic property.