Research On The Effects Of Sulfate Ions, PH, Temperature And Chloride Ions On The Anodic Polarization Behaviour Of Nanocrystalline Copper

The influence of sulfate ions, PH, temperature and chloride ions on the anodic polarization behaviour of nanocrystalline copper (nano-Cu), prepared by an inert gas condensation and in-situ warm compacting technique, was investigated using a potentiodynamic polarization method. Meanwhile, the field emission gun scanning electron microscopy and x-ray energy dispersive spectroscopy were used to characterize the morphology and chemical composition of corrosion products. The results showed that the sulfate ions, chloride ions, PH and temperature play important role on the anodic polarization behaviour of nano-Cu. In the case of Na2SO4 solution, the critical current increases with increasing sulfate ion concentration and the slope of the log i vs sulfate ion concentration is 0.01158. However, the critical potential decreases as sulfate ion concentration increases. A model of "electrostatic ion clusters" was proposed for interpreting the "slope pivotal point" occurring on the anodic polarization curves. In addition, the corrosion mechanism of nano-Cu in Na2SO4 solution and the kinetic equation were proposed. The variation of log i with PH fits the following linear relation, logi=-0.0287PH +0.25. An increasing H+ concentration disturbs the formation of oxidation film, resulting in an increased rate of electrodissolution .The variation of logi vs 1/T could be described as log i= -669.94(l/T)+2.4388. On the base of Arrenhenius equation, the influence of temperature on the anodic polarization behaviour was analyzed. In the case of NaCl solution the current oscillation of nano-Cu electrode in 1.5%NaCl solution was observed and concerned with the non-linear Cu(II) dissolution processes. The main corrosion products of nano-Cu in Na2SO4 solution are Cu2O cubic crystallites with different size, which is dependent on the temperature of Na2SO4 solution. For example, the size of the Cu2O cubic crystallites closely stacked on the electrode surface varies from about 200 nm to about 50nm when the temperature of Na2SO4 increases from 25 ℃ to 40 ℃. On the other hand, the main corrosion products of nano-Cu in NaCl solution are CuCl and Cu2O crystallites. The grooves appear on the surface of electrode, indicating that these areas are heavily corroded. The shape and size of CuCl and Cu2O crystallites are different at the different site of the top, middle and bottom of these grooves.