Study On Preparation Of Superhydrophobic Surface And Corrosion Resistance Of Magnesium Alloy

Magnesium and magnesium alloy are widely used in fields as communications andtransportation grounded on the outstanding performance, such as high specific strength andhigh specific modulus, easily cut and machined, low processing cost, good ductibility, andexcellent hot scatter, etc. However, the application of the magnesium and its alloy is limiteddue to the bad corrosion resistance of magnesium in the humid atmosphere. On the other hand,the superhydrophobic surface can delay and reduce the corrosion of materials due to its strongwater-repellent abilitysuperhydrophobic. Thereupon, the corrosion resistance of magnesiumand its alloy can be improved effectively by preparaing the superhydrophobic coating on themagnesium alloy surfaces which is quite important for enhancing the corrosion resistance andwidening the application range of magnesium and its alloy.In this research, the superhydrophobic coatings on AZ31magnesium alloy surfaces wereprepared by dilute sulfuric acid etching-stearic acid grafting method, then thesuperhydrophobic coatings on AZ91magnesium alloy surfaces were prepared by dilutesulphuric acid etching-dodecyl mercaptan modification method, and the fabrication process,technical parameters, chemical structure, surface morphology, phase structure, and corrosionresistance, etc. were investigated in detail. The main contents and results are listed as follows:(1) After etched in dilute sulfuric acid, the AZ31magnesium alloy was modified withstearic acid for some time. And then the surface of AZ31magnesium alloy with thesuperhydrophobic performance was rusulted. The wettability, surface morphology, chemicalcomposition, and structure of the superhydrophobic surface was characterized by techniquesas contact angle measurement, SEM, and the infrared spectroscopy. Results show that thelargest surface contact angle at AZ31magnesium alloys can reach153°while the rollingangle is less than10°. A great deal of flower-like structure with micro-and nano-scales, onwhich long stearic acid hydrophobic chains were grafted, was observed on AZ31surfaces. Asa result, the surface of AZ31magnesium alloy was endowed with superhydrophobicperformance. The contact angle remains basically unchanged after the preparedsuperhydrophobic specimen was placed at room temperature for3months, suggesting that thesuperhydrophobic coating at AZ31magnesium alloy has excellent stability.(2) Put the AZ91magnesium alloy in dilute sulfuric acid to etching. It is used silver nitrateas oscillatory reaction solution. After put the simple device into the twelve ethanol solutionfor some time, cleaning, dried in room temperature, we obtained the surface of AZ91magnesium alloy with superhydrophobic performance. The wettability, surface morphology,chemical composition, structure, and corrosion resistance of superhydrophobic surface wascharacterized by contact angle measurement, SEM, infrared absorption spectroscopy and electrochemical workstation. Results show that the best surface contact angle of AZ91magnesium alloy was154°while the rolling angle is less than10°. The surface has a largenumber of coralline micro nano structure and solvothermal hydrophobic long chain，whichmakes the surface of AZ91magnesium alloy with superhydrophobic performance. Thecontact angle remains basically unchanged after the prepared superhydrophobic specimen wasplaced at room temperature for3months, suggesting that the superhydrophobic coating atAZ91magnesium alloy has excellent stability.(3) The corrosion resistance of AZ31and AZ91with different contact angles are analyzedby electrochemical analysis, and results show that: the corrosion resistance of thesuperhydrophobic magnesium is higher than that of the untreated AZ31and AZ91. Further,the corrosion resistance enhances with the increase of the contact angle. These indicate thatthe superhydrophobic magnesium alloys have better corrosion resistance.