Basic Research On The Corrosion Resistance Coating Of The Steel Surface Prepared By Titanium Bearing Blast Furnace Slag

The electrolytic medium of traditional electrochemical preparation of titanium metal is mainly pure chloride,preparation of titanium metal powder.In the NaCl-KCl-NaF molten salt system,the carbon steel is the working electrode,and the titanium metal anticorrosive coating can be prepared on its surface.Titanium coating not only improves the corrosion resistance of carbon steel substrate,but also provides a more simple process to obtain titanium metal,which combines the carbon steel substrate mechanical properties and corrosion resistance of titanium together.The characteristics of melting and dissolution of TiO₂ in NaCl-KCl-NaF molten salt system were analyzed by isothermal saturation method.The saturated solution time of TiO₂ in molten salt system is determined as 4.0h.The solubility of TiO₂ in the molten salt system increases with the increase of NaF mole fraction.The results of differential thermal analysis?DTA?of molten salt system with different proportions show that when the Na F content is low,TiO₂ affects the initial crystallization temperature of the molten salt system,and when the NaF content is higher,the initial crystal temperature remains unchanged with the change of mass fraction of TiO₂.The electrochemical reduction mechanism of Ti?IV?ions in NaCl-KCl-Na F-TiO₂ molten salt system is investigated by cyclic voltammetry and square wave voltammetry.The results from the experiments can be determined that the Ti?IV?ions are reduced to titanium metal by three steps,namely Ti?IV?-Ti?III?-?II?-Ti,and the reduction process is irreversible.The nucleation mechanism of titanium ions on the cathode surface is determined as three dimensional hemispherical instant nucleation process by the chronoamperometry.The experimental results show that the quality of titanium coating is best when the deposition temperature is 800 ?,the deposition current is 1.5A and the deposition time is 1.0h;By comparing the surface morphology of the DC electrodeposited and the pulsed electrodeposited samples,it can be determined that the grain size of the titanium coating obtained by pulsed electrodeposition is smaller,and the deposited layer is more compact and uniform,and the surface is flat.The corrosion resistance of the deposited samples was investigated by polarization curves and AC impedance measurements in 3.5% NaCl solution.The test results show that the corrosion resistance of the sample is the best when the deposition current is 1.5A and the deposition time is 1.0h.Compared with the carbon steel substrate,even if only a small amount of titanium deposited on the carbon steel surface,it can significantly improve the corrosion resistance of the steel substrate.And the corrosion characteristics of the pulsed deposition samples are better than those of the DC samples.