Study To The Technology Of Non-cyanide Zinc Dipping Of Aluminum And Aluminum Alloy

At the base of understanding the actuality of non-cyanide zinc dipping,the effects of temperature,additives,zincates and Multiple Alloying on the process of non-cyanide zinc dipping were investigated,and the disposal effects of different zinc dipping was analyzed in contrast;The morphology of different zinc dipping conditions was studied by SEM,and the composition of the zincation film was determined by EDX and the steady potential with the changing of the immersion zinc temperature was researched.Through these studies and the immersion tests,the perfect technology of non-cyanide zinc dipping was confirmed.The main contents and conclusions of this thesis were as follows:1.Usually,non-cyanide zinc dipping solution contains two or more additives to improve the performance of zinc dipping solution.This experiment selected C₆H₁₁O₇Na,NaNO₃,monoethanolamine and ethylene thiourea additives,and used scanning electron microscopy(SEM),X-ray spectrometer studying the effects of zinc dipping process of the complexing agents and inhibitors.The results show that different complexing agents on the zinc dipping process has significant effects; NaNO₃ used as Corrosion Inhibitors has a great impact on stable potentia in first zinc-dipping;glucose and NaNO₃,when used together having good effect.However, monoethanolamine makes zinc dipping layer coarsening.Inhibitors can reduce the leaching of zinc of zinc layer to obtain the crystallization of refinement effectively.2.In order to acquire a coating with big bonding strength on high-silicon aluminum castings,the technology of non-cyanide zinc dipping was optimized.The effects of ZnO,ZnSO₄ and other zincates containing different anions,inhibitors on the steady potential and the morphology in process of zinc dipping were studied by SEM and X-ray energy spectrometer.Through experiments optimum zinc dipping technology was established:80.0g/L NaOH,12.50g/L NiCl₂,0.6g/L CuSO₄,0.8g/L FeCl₃,25.0g/L Zn(NO₃)₂,1.00g/L NaNO₃,12.50g/L C₆H₁₁O₇Na,0.20g/L 2-Mercapto-imidazoline.The results show that Zn(NO₃)₂ is more effective than other zincates to get a thinner and uniformer zincation film.The inhibitors can reduce the Zn content of Zn film effectively and form a thinner zincate layer.It is proved that the effect of zincation is optimum to get a strong adhesion of the plated metal over the zincated aluminum when Zn(NO₃)₂,complexing agents and inhibitors are used together.3.The effects of immersion zinc temperature on the steady potential and the microstructure of the immersion zinc layer on A356 alloy in process of zinc dipping and the adhesion capacity of the nickel-plate had been investigated by SEM,EDX and CHI600B electrochemistry workstation.The results show that the steady potential gets bigger with the increasing of the immersion zinc temperature,which is help to get finer zinc grain.The zincation film is getting finer,compacter,slipperier and more homogeneous,while the percent of Zn on the film is lower and the percents of Fe,Cu and Ni are appropriate when the temperature reach to 25℃.However,higher immersion temperature resulted in the steady potential removing negatively and the effect of zincation becoming worse,and finally leading to the zinc layer flaking off from the matrix when it getting to 35℃.There is a exceptional response of the potential removing negatively greatly between 20℃and 30℃,and the optimized immersion temperature is 25℃by the steady potential-temperature test.It is proved that a strong adhesion of the plated metal over the zincated aluminum can be get between 20℃and 30℃.4,Try to add Cobalt ions into the traditional alloy liquid cyanide-free zinc dipping,and study the effects of multi-alloy non-cyanide leaching by changing the cyanide-free zinc dipping liquid constituents.By Scanning Electron Microscopy researching zinc layer morphology,as well as X-ray spectrometer for different formulations of zinc dipping the metal layer analysis to determine the leaching of zinc,showing that Cobalt-Nickel-Iron,Cobalt-Nickel-Copper zinc dipping and Cobalt-Nickel-Zinc Dipping have better effects than the traditional Iron-Nickel-Copper quaternary alloy zinc dipping solution;Co²⁺ is Conducive to the crystallization of refinement.