Corrosion Behavior And Inhibitors Of Bulk Nanocrystalline Copper

Potentiodynamic polarization technique, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to investigate the corrosion behavior of nanocrystalline copper (NC Cu) bulk prepared by inert gas condensation and in situ warm compass (IGCWC) technique in ammonia solution. The effect of temperature on corrosion behavior of NC Cu bulk in HNO3 solution and the inhibition effect of 3,5-dinitrosalicylic acid (DNS), histidine and isoleucine for copper in nitric acid were also studied. Meanwhile, the differences in corrosion behavior between NC copper and coarse-grained copper (CG Cu) in the same corrosion environment were compared and analyzed. This research has drawn the following conclusions:1. NC Cu displayed an active-passive-transpassive behavior with the formation of duplex passive films but without stable passive regions in 0.3 wt.% ammonia solution. In passivation process, the bamboo-leaf-like passive film is composed of CuO and Cu(OH)2. NC Cu exhibited slightly inferior corrosion resistance when compared with CGCu. It could be explained by both the higher grain boundary density that could accelerate corrosion reactions and the loose passive film formed on the surface of NC Cu that couldn’t provide effective protection.2. Temperature has a greater effect on NC Cu in 0.1 M HNO3 solution, owning to its higher driving force. In deaerated solution, temperature has the same influence on the corrosion resistance of CG Cu and NC Cu that decreases with the increasing temperature. Nevertheless, in naturally aerated HNO3 solution, different from CG Cu, the corrosion resistance of NC Cu increases with increasing temperature until 55℃, at which the corrosion current density of the two were even identical. It was attributed to the sensibility for O2 traces of NC copper. After 55℃, identical to CG Cu, the corrosion resistance of NC Cu decreases with increasing temperature.3. DNS has been evaluated to be a new high-efficiency mixed-type inhibitor for copper in 0.1 M HNO3, with maximum efficiency of 92.43% at a concentration of 5 mM. The adsorption behavior of DNS followed Langmuir’s isotherm. Physisorption was contributed to the adsorptive behavior of DNS. The inhibitive effect decreased by increasing the temperature in the range of 25-55℃, and temperature has a greater effect on the inhibition of DNS on NC Cu.4. Histidine and isoleucine have been proved to be green inhibitors for copper in HNO3 solution. They are considered as mixed-type inhibitors, but mainly inhibit the cathodic process. Both physisorption and chemisorptions contribute to the adsorptive behavior of histidine and isoleucine. Because of the difference in free energy of adsorption between histidine and isoleucine on Cu, the inhibitive effects of them on copper are different. Compared with CG Cu, the concentration of amino acid on NC Cu is higher and the inhibitive effect is better, owing to an increase of surface energy and a higher density of active sites of NC Cu.