Study On The Process Of Preparing Super-hydrophobic Surface On Steel Substrate By A Novel Ni-nSiO₂ Nano Composite Electro-deposition Method

Because of its much excellent performance, such as self-cleaning, anti-biofouling, low water friction resistance, high bearing capacity and brilliant corrosion resistance, super-hydrophobic surface can be widely applied in the ship and ocean engineering. However, the current study on preparation of super-hydrophobic surface on steel substrate is still not satisfactory. Besides, the preparation process of super-hydrophobic surface is still in the stage of laboratory research and is not quite close contact with the actual production. Considering the ship and ocean engineering practical application condition, a preparation technique of super-hydrophobic surface on steel substrate with simple preparation process, high preparation efficiency, easy to repeat and product on large area is needed. Reference to traditional composite plating and composite brush plating method, a novel technique of preparing the super-hydrophobic surface on steel substrate by Ni-nSiO2 nano composite electro-deposition method is proposed. By building micro-nano Ni-nSiO2 coating, the super-hydrophobic surface on Q235 substrate is prepared. Specific study content includes the following points:Firstly, with the merits of composite plating and composite brush plating, the nano composite electroplating equipment is designed and improved which allows large-scale production and increases the level of automation. The application of shading auxiliary anode, circulation feeding system and electromagnetic stirring device can achieve the uniform distribution of nanoparticles and metal ion to ensure a more evenly coating. In order to increase the cathodic polarization properly and refine obtained coating surface, the fast nickel plating solution formula is adjusted to avoid the high porosity, as a result, there is no obvious large pores on coating any more. The requirement of Q235 substrate becomes lower, utilizing the advantages of rough surface which makes nanoparticles easily to stick and stay as well as adapting to the practical production.Secondly, choosing the orthogonal experiment design method to get a lot of experimental data and at the same time the relationship between the Ni2+ concentration, current density, anode speed, deposition time and contact angle of surface are analyzed respectively. After the range analysis and some related mathematic methods, it is found that current density is the main factor in super-hydrophobic performance of coating among all selected process parameters.Finally, the reason why surface is super-hydrophobic has got from the analysis of surface roughness and surface morphology. The obtained complex structure of micron, submicron and nanoscale construct the binary rough structure which realizes the super-hydrophobic function of the surface. Comparison of samples as-prepared by qualitative and quantitative methods, the conclusion is reached that when the Ni2+ concentration is 127 g/L (0.5 mol/L), current density is 37.5 A/dm2, anode speed is 8 m/min, depositon time is 5 min, a super-hydrophobic surface with contact angle is 153.5°, rolling angle is 6.5° can be prepared. This super-hydrophobic coating has many comprehensive properties, such as good self-cleaning, strong binding force, high hardness and well corrosion resistance.