Study On The Hydrophobic Property And Corrosion Mechanism Of Fe-based Amorphous Metallic Coatings

With the continuous exploration of bionics,the micro-nano bionic superhydrophobic interface based on the self-cleaning effect of lotus leaf surface has gradually become a research hotspot.Amorphous alloy is an ideal material for fabricating micro-nano structures due to its small homogeneity and forming limit at atomic scale.However,the existence of oxide inclusions and pores during the spraying process of Fe-based amorphous metallic coating(AMC)will cause the local corrosion,especially the initiation of pitting.The construction of bionic hydrophobic interface can effectively control the pitting resistance of amorphous metallic coatings,but the design and preparation of micro-nano structure of amorphous materials are still lack of scientific basis.In this paper,the influence of different etching processes such as chemical etching time and etchant concentration on the micro-nano structure and hydrophobic properties of Fe-based AMC was analyzed by the combination of macro and micro analysis methods,and the hydrophobic mechanism of the AMC was explored.The relationship between surface structure and corrosion resistance of hydrophobic AMC was determined by electrochemical testing.Combined with thermal spraying process,AMC with different powder sizes were prepared,and the influence mechanism of powder size on hydrophobic structure and corrosion resistance of AMC was studied.After chemical etching,the surface of AMC is composed of unmelted particles,micro synapses,pores and surface pits.With the increase of etching concentration and etching time,the solid-liquid contact fraction and surface energy of the AMC decrease first and then increase.When etching for 60min in 3mol/L HCl,the surface contact angle of the AMC reaches 142.58°and the surface micro-nano structure composed of corrosion products,pores and unmelted particles,which is most consistent with Cassie-Baxter model and close to superhydrophobic surface.In 3.5%Na Cl solution,the hydrophobic AMC prepared by this etching process exhibits the smallest passivation current density and the largest capacitive arc radius.The micro-nano hydrophobic structure and the organic hydrophobic layer on the surface of the AMC can effectively isolate the contact between the corrosion solution and the substrate,delay the contact time between Cl~-and the oxide inclusion of the AMC,and the coating shows the best uniform corrosion resistance.When spraying,the reduction of powder particle size(300 mesh,400 mesh,500 mesh)can effectively reduce the porosity of AMC surface and increase the content of oxide.After hydrophobic treatment,the micro-nano structure of AMC prepared with 400 mesh powder is closer to Cassie-Baxter model than that with 300 mesh powder,and the contact angle is152.11°.The micro-nano structure constructed on the surface has the most uniform distribution,the lowest surface energy and superhydrophobicity.When the particle size is 500mesh,there is serious agglomeration on the AMC surface,and the integrity of micro-nano structure is destroyed.Electrochemical analysis shows that the hydrophobic AMC prepared by 400 mesh has the highest passivation current density and the best uniform corrosion resistance.After 90 days of immersion corrosion,the hydrophobic layer structure can remain stable in the corrosive environment and exhibits enhanced long-term corrosion resistance.