Study On The Al-Ni Alloy Plating And Micro-arc Oxidation Film

In this thesis, the Al-Ni alloy coatings were electrodeposited on Q235steel surfacefrom AlCl3-NaCl-KCl molten salts in which the different contents of NiCl2were added.The surface morphology, phase structure and hardness of obtained Al-Ni alloy weredetermined by Ni content in the deposits. The surface morphology、components andstructure of the coatings were investigated by scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The polarizationcurves, electrochemical impedance spectroscopy and anodic polarization curve wereperformed in3.5wt%NaCl solution aiming to evaluate the corrosion resistance of thecoatings. The even surface morphology of the coatings could be obtained when the contentof Ni was5.17%, which grains almost disappeared and grain boundaries became blurred.The coating elements are mainly composed of Al and Al-Ni alloy phases. The content ofNi plays an important role in the corrosion resistance of the coatings. The corrosionresistance and hardness are excellent when the content of Ni was5.17%.In this experiment, the Al-Ni alloy was plated on steel surface by molten saltelectroplate. The plating were turned into Al-Ni alloy micro-arc oxidation coatings whichis more uniform by micro-arc oxidation (MAO). The electrolyte consistence concentration,oxide voltage, oxide time and different kinds of additives were tested aiming to find thebest processing parameters. The surface morphology and structure of the ceramicmembrane were tested by SEM and XRD. The polarization curves and electrochemicalimpedance spectroscopy were investigated in3.5wt%NaCl solution to evaluate thecorrosion resistance of Al-Ni alloy micro-arc oxidation coatings. The results showed thatthe even surface morphology of Al-Ni alloy micro-arc oxidation coatings could beobtained at different additives, especially the film was more uniform and dense, and thedischarge channel diameter was smaller by adding Na2WO4. The Al-Ni alloy micro-arcoxidation coatings is mainly composed of Al, Al2O3and AlNi3, and aluminum and nickelexist in the form of Al-Ni alloy. The ceramic membrane has better corrosion resistance,thickness and hardness by adding different kinds of additives, the film has the bestcorrosion resistance by adding1.5g/L Na2WO4especially.