Fabrication Of Titanium-alloy Superhydrophobic Surface And Its Corrosion Resistance Property

Titanium alloy have been widely used in various fields such as marine industry,aviation,petrolchemical industry and bio-medical industry due to their splendid corrosion resistance,high specific strength and excellent biocompatibility.Titanium can easily react to oxygen at room temperature to generate compact oxidation film,which has been regarded as one of the most efficient corrosion-resistant materials in marine environment.However,it's quite difficult for oxidation film to repair once destroyed in oxygen-deficient environment.Besides,it also easily suffers hydrogen embrittlement fracture owing to the hydrogen evolution when coupled with other metal material.In recent years,inspired by "lotus effect",superhydrophobic surface has attracted more and more attention because it could largely reduce the corrosion of the metal materials.Therefore,it would be of great practical significance to help improve the corrosion resistance in sea water by studying the technique to construct the superhydrophobic surface of Titanium alloys.First,geometric model of microgroove array is designed,and analyze the relationship between the geometric parameters and the surface contact angel(SCA)in Wenzel wetting condition and Cassie-Baxter condition,respectively.In Wenzel condition,SCA will increase with the increase of A(the ratio of the width to the space between the microgrooves),but decrease with the increase of B(the ratio of the height to the space between the microgrooves).In Cassie-Baxter condition,SCA will increase with the increase of A,but decrease with the increase of a(groove angel),which demonstrates that it should increase the width and ?,also decrease the space between the microgrooves to acquire better hydrophobicity.Although B has little influence on the SCA,the larger B could lead to the decline of the mechanical property,and the smaller B could make the water penetrate into the microgrooves easily to transform into the Wenzel condition.Hence,it should limit B to a proper range.At last,verification experiment is designed which demonstrates the consistency between the experimental value and the theoretical value.Then,considering the hard machinability of TC4,in whose micromachining process burrs are easily generated,optimization experiment of cutting parameters is designed to analyze the relationship between the feed per tooth,spindle rotation speed,depth of cut in axial direction.Besides,PMMA was used as the support material to help restrain the burrs generation in micro-milling.Compared with other methods,it owns the advantages of flexible preparation,simple coating process and so on.Experiment also demonstrates that it owns the better property of burrs restriction.Finally,taking the microgrooves as the basement,membrane with micro/nano structure is constructed on TC4 surface through sol-gel process,which mainly consists of anatase titanium dioxide.Messes of nano bulges with the size of 30-50nm are found on the membrane,which shows better superhydrophobicity with the SCA of 152.4° and surface energy of 24.4mJ·m-2.After examined by the electrochemical workstation,polarization curve of the corrosion in simulated sea water is obtained.Results demonstrate that,compared with the untreated ones,TC4 surface with the membrane has higher corrosion potential and lower corrosion current density.