The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical me...The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry,open circuit potential transition,electrochemical impedance spectroscopy,scanning electron microscopy and X-ray photoelectron spectrometry.It is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode surface.And the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance,lower polarization resistance,and higher capacitance in a corrosive atmosphere.It is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol,which means easier electrochemical codeposition of chromium and carbon,not single chromium deposition.展开更多
The influences of sodium silicate on manganese electrodeposition in sulfate solution were investigated. Manganese electrodeposition experiments indicate that a certain amount of sodium silicate can improve cathode cur...The influences of sodium silicate on manganese electrodeposition in sulfate solution were investigated. Manganese electrodeposition experiments indicate that a certain amount of sodium silicate can improve cathode current efficiency and initial pH 7.0?8.0 is the optimized pH for high cathode current efficiency. The analyses of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate the compact morphology and nanocrystalline structure of electrodeposits. X-ray photoelectron spectrometry (XPS) analysis shows that the elements of Mn, Si and O exist in the deposit. The solution chemistry calculations of sulfate electrolyte and sodium silicate solution indicate that species of Mn2+, MnSO4, Mn(SO4)2?2 , Mn2+, MnSiO3, Mn(NH3)2+, SiO32?and HSiO3? are the main active species during the process of manganese electrodeposition. The reaction trend between Mn2+ and Si-containing ions is confirmed by the thermodynamic analysis. In addition, polarization curve tests confirm that sodium silicate can increase the overpotential of hydrogen evolution reaction, and then indirectly improve the cathode current efficiency.展开更多
文摘The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry,open circuit potential transition,electrochemical impedance spectroscopy,scanning electron microscopy and X-ray photoelectron spectrometry.It is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode surface.And the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance,lower polarization resistance,and higher capacitance in a corrosive atmosphere.It is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol,which means easier electrochemical codeposition of chromium and carbon,not single chromium deposition.
基金Project(2015BAB17B01)supported by the National Science and Technology Support Program of ChinaProject(21376273)supported by the National Natural Science Foundation of China
文摘The influences of sodium silicate on manganese electrodeposition in sulfate solution were investigated. Manganese electrodeposition experiments indicate that a certain amount of sodium silicate can improve cathode current efficiency and initial pH 7.0?8.0 is the optimized pH for high cathode current efficiency. The analyses of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate the compact morphology and nanocrystalline structure of electrodeposits. X-ray photoelectron spectrometry (XPS) analysis shows that the elements of Mn, Si and O exist in the deposit. The solution chemistry calculations of sulfate electrolyte and sodium silicate solution indicate that species of Mn2+, MnSO4, Mn(SO4)2?2 , Mn2+, MnSiO3, Mn(NH3)2+, SiO32?and HSiO3? are the main active species during the process of manganese electrodeposition. The reaction trend between Mn2+ and Si-containing ions is confirmed by the thermodynamic analysis. In addition, polarization curve tests confirm that sodium silicate can increase the overpotential of hydrogen evolution reaction, and then indirectly improve the cathode current efficiency.
