Study On Amorphous Iron-chromium Alloy Electrodepositing From Trivalent Chromium Bath

For resolve the serious pollution of the environment of hexavalent chromium plating, and for economize the chromium resources and energy, electrodeposition amorphous chromium-iron alloy from trivalent chromium electrolyte now has been extensive investigated. Electrodepositied amorphous chromium-iron alloy from trivalent chromium electrolyte, the paper studied the influence of changes in the concentration of glycine, current density, temperature and pH on Cr% of deposits. It is also studied that the effect of additive and impurity ion on electrodeposition. Surface morphology of amorphous chromium-iron alloy deposit from electrolyte cotaining addtives and for different times were investigated by scan electron microscope (SEM). The composition of blue film of electrodeposited prosess and the state of deposit's metal element were studied by X-ray photoelectron spectroscopy (XPS).Crystal structure of deposits with different metal percent was analyzed by X-ray diffraction (XRD). Corrosion resistance of deposits was compared between crystalloid and amorphous state by anodic polarization curves. The action of the glycine and each metal ion in trivalent chromium electrolyte electroplating chromium-iron alloy were briefly discussed by linear sweep voltammetry (LSV) and calculation of action energies.Experiments show: electrodeposited in selected operation conditions, chromium-iron alloy deposit had a bright appearance and exhibited good adhesion on copper, whose Cr% was beyond 30wt%. The deposit has amorphous state and better corrosion resistance than crystalloid deposit. The impurity ion such as Cr6+, Fe3+ affect the quality of deposit, which can be get rid of by ascorbic acid. The selected additive NaF can enlarge the cathodic polarization, amplification the electrodeposition scope of low electric current density and increase the deposit's shining. In the electrolyte the glycine reacted mainly with Fe(II) ion, which go up the Fe(II) action energy to increase cathodic polarization. Thus the deposited potential of Fe( II) become more negative ,and electrodeposite with chromium.