| The corrosior.of Magnesium allays is mainly to electrochemical corrosion,thus prevert the entry of water melecules can effectively improve the corrosion esistance of magnesium alloy.The low surface energy and rough structure are the two main factors to fabricate the super-hydrophobic surface,and the forme is the basic condition for changing the wettability,the latter is the main factor.This work was to generate heterogenecus ceramic coating with different rough structure by controlling the micro-arc oxidation time.The effect of toughness structure of the heterogeneous material on the contact angle was studed.The:process parameters for fabricate the super-hydrophobic surface by combination of acrylic acid etching and stearic acid modifying on magnesium alloy micro-arc oxidation ceramic was studied.The the corrosior resistance of different wetability of ceramic layer and the effect cf super-hydrophobic surface on the corrosion behavior of the micrc-arc oxidation ceramic within the different immersicn stages were investigated via the elect rochemical corrosion experiment.The result showedThe surface roughness structure of heterogeneous material has great influence on the contact angle.For the hydrophilic MgO ceramic coating,the surface roughness Sa was to represent the roughness factor,the contact angle decreases from 78° to 16° with the Sa increases from 0.25?m tc 1.787?m,and when the contact angle is close to super hydrophilic,the greater the dispersion of the contact angle with the increasing of pore size distribution range of the ceramic coating.For the hydrophobic ceramic coating modified with stearic acid,when the contact angle is less than 148°,the contact angle increases with roughness increases of ceramic layer,and when the contact angle is close to 150°,the linear relationship between contact angle and roughness is reduced,and the fractal dimension(FD)was represents to the roughness factor,the contact angle from 148° to 159° with the FD increases from 1.66 to 1.95.The super hydrophobic surface can be fabricated on the micro-arc oxidation ceramic coating combined with the acrylic acid etching and stearic acid modifying.The best process parameters for fabricate the super-hydrophobic surface:micro-arc oxidation time 25min,acid etching parameters of 40?,0.08mol/L,and the modifying parameters of 60?,0.1mol/L.and the static contact angle is 159°,the rolling angle is less than 3°.The super-hydrophobic ceramic coating was placed in the air for 30 days,the contact angle decrease from 159° to 153°,still has super hydrophobic.The smooth convex surface formed by natural melting of ceramic coating was changed by the acrylic acid etching,The distribution structure on the surface is about 1?m and the strip structure ranging from 100nm to 200nm,the micro-nano rough structure were formed.The different surface wettability of the micro-arc oxidation ceramic coating of magnesium alloy can effectively improve the corrosion resistance of ceramic coating,the larger the contact angle the better corrosion resistance.The corrosion current is reduced by 3 orders of magnitude,the super-hydrophobic ceramic coating than the hydrophobic ceramic coating,when the contact angle is 159°,the corrosion current is 3.3134×10-9A/cm2.Compared with the hydrophilic ceramic coating,the impedance value increases 1.3×106? of the super-hydrophobic ceramic coating in the early immersion,and the final failure time delayed 240min.The micro-nano structure on the super-hydrophobic ceramic coating reduces the actual contact area of the water with the ceramic coating of 97%,thus which effective decrease the speed and quantity of water molecules entry into the ceramic coating during the initial period of immersion,and slow down the hydrogen evolution corrosion reaction in cathode,and so the speed of electrochemical corrosion reaction is slowed. |
PDF Full Text Request