Study On Non Cyanide Electroplating Process And Electrodeposition Behavior Of Cadmium Titanium Alloy

Non cyanide plating Cd-Ti alloy coating can be used as a protective coating of high strength steel,the micro titanium?0.1-0.7%?in the coating has a great influence on the hydrogen embrittlement and corrosion resistance of the coating.However,in practical production,there are still some technical problems such as the difficult control of titanium content in the coating,the insufficient stability of the plating bath and the hydrolysis,which hinders the popularization and application of the technology.In this paper,Cd-Ti alloy coating was prepared by electro deposition method based on the bath of cadmium coating on neutral ammonium salt and the addition of self-made titanium oxychloride,the polarization curve method and X ray photoelectron spectroscopy?XPS?explored Cd-Ti alloy electro deposition behavior,scanning electron microscopy?SEM?,X ray diffraction?XRD?to observe the surface morphology and crystal plane orientation,studied the influence of process parameters on the content of titanium coatings by single factor experiment,the stability of the bath was studied by "aging" experiment and "continuous plating" experiment.The main results are as follows:1.The Ti ion in the bath did not undergo electrochemical reaction on the cathode surface,but reacted with OH-at the cathode interface to form TiO2 and a small amount of Ti₂O₃,which was mixed with the cadmium coating.The deposition process is assumed to be:TiO²⁺+OH-? TiO²⁺H+TiO²⁺+H? TiO⁺+H+2TiO⁺+2OH-? Ti₂O₃+H₂OThe introduction of titanium salt in the bath increases the cathodic polarization of the working current density region,increases the nucleation overpotential of the cadmium and reduces the grain size of the coating.2.Self-made salt titanium oxychloride,and hydrochloric acid to titanium ratio control 1:4?g/ml?,the introduction of the self-made titanium oxychloride neutral ammonium cadmium plating bath?titanium content?is 4-5 g/L,and the titanium and cadmium of solution in the proportion of 1:3,the plating current density is 2-3 A/dm²,can access 10 ?m Cd-Ti alloy coating for maize,titanium content up to about 0.4%,and the bath can be long-term stability.3.The surface of pure cadmium coating is dark gray,the crystalline is rough,and the preferred orientation is?101?and?002?,the deposition type is inclined type coating,and the Cd-Ti alloy coating?titanium content is about 0.5%?is obtained by introducing self-made titanium oxychloride in the bath,and the surface is maize with fine crystallization,in?101?,?100?and?110?planes are preferred orientation,and the deposition type is a vertical coating,the introduction of titanium changes the preferred orientation and deposition type of the coating,which is favorable for the release of hydrogen and reduces the possibility of hydrogen embrittlement.In addition,the self corrosion potential of the cadmium titanium alloy coating is-0.825 V,and the self corrosion current density is 1.765? 10-2A/dm².The self corrosion potential correction of the cadmium coating is smaller than that of the pure cadmium coating,and the corrosion current density is smaller,and the corrosion resistance of the coating is enhanced.4."Aging" test and "continuous plating" experimental study show that: when the pH value of the new bath is 5.99 and 7.05,the stability constants of the bath are 0.886 and 0.873 respectively,18 days later,the bath has turbidity,when the pH value is 6.7,the stability constant is 0.946.The Cd-Ti alloy plating bath at 10-60 ? for long-term storage,no precipitation,but the temperature is higher than 60 ?,the bath to produce white turbidity,precipitation products are mainly Ti?OH?₄,TiO₂,H₂Ti₂O₁₁,3H₂ O,NH₄Cl.During the continuous plating process of the newly prepared 25 L plating solution,the power consumption was 2.07?10⁶C and the titanium content reached the peak value after 16 days of plating.After 28 days,the power consumption was3.63 ? 10⁶,and the content of titanium in the coating was less than 0.1%,the plating bath complexing agent consumption faster,need to re-analysis of the composition of the supplementary bath to ensure its long-term stable production.