Study On Electrodeposition Of Tin-Fe Alloy In Sodium Gluconate System

At present,Sn-Fe alloy is mainly prepared by thermal diffusion method in industrial production.The intermetallic compound layer（Fe Sn₂）is formed in the soft melting process of tinplate,and then improve the corrosion resistance of the coating.Today electrodeposition of Sn-Fe alloys has been successfully developed,the coating by means of the electrodeposition process of Sn-Fe alloy has excellent corrosion resistance.However,the bath can not be preserved for a long time because of its poor stability,and the consumption and addition of main salt ions need be further studied in the working process of bath.Meanwhile,the internal stress of Sn-Fe alloy coating limits its application.Resveratrol,hydroquinone and tert-butylhydroquinone（TBHQ）were selected as the stabilizer of Sn-Fe alloy bath obtained antioxidant ability test and Fe²⁺complexing ability test.The effects of stabilizer on stability,dispersion and covering ability of bath,corrosion resistance,surface morphology,composition,phase structure and current efficiency of coating were studied.The experimental results show that compared with hydroquinone and TBHQ,resveratrol has the strongest antioxidant capacity and the best improvement effect on the stability of the bath.Moreover,adding an appropriate amount of resveratrol into the bath is good for improving the corrosion resistance of the coating.The higher the resveratrol concentration,the stronger the stability of the plating solution.However,salt spray test and electrochemical impedance spectroscopy（EIS）test results illustrated that excessive resveratrol reduces the corrosion resistance of Sn-Fe alloy coating.Therefore,the optimal concentration of resveratrol in the bath was 1.0g/L considering the stability of the bath and the corrosion resistance of the coating.The orthogonal experiment was used to optimize the process of pulse electrodeposition of Sn-Fe alloy,the results present that the optimum experimental parameter of pulse electrodeposition is as follows:peak current density 3.0A/dm²,duty cycle 0.2,pulse frequency250Hz.The effect of pulse parameters on internal stress of Sn-Fe alloy coating was confirmed by single factor experiment.The higher the peak current density,the greater the stress in the coating,the higher the duty cycle and pulse frequency,the lower the stress in the coating.Moreover,the effect of pulse electrodeposition process on Sn-Fe alloy coating was studied.Salt spray test,EIS test and Tafel curve results show that pulse electrodeposition can improve the corrosion resistance of coatings.EDS results illustrate that pulse electrodeposition can reduce the Fe content of the coating.Meanwhile,efficiency of current was measured,and the result confirmed that can improve the efficiency of current,because the off time supply is conducive to the release and escape of hydrogen and other impurities during the electrodeposition process.The new type of Sn and Fe double anode electrodeposition process was developed to solve the problem of consumption and addition of Sn²⁺and Fe²⁺in the bath.The polarization curves of Sn anode and Fe anode show that the single control mode with double anode is adopted.The anodic dissolution experiment results show that the area ratio of Sn and Fe anodes is 2.31:1.The effects of different anode processes on the ionic balance of the bath and the corrosion resistance,surface morphology,composition,composition and current efficiency of the coating were studied.The experimental results illustrate that the double-anode electrodeposition can significantly improve the working life of the bath and corrosion resistance of the coating.