Role Of UV Illumination On The NaCl-induced Atmospheric Corrosion Of Pure Copper

The effects of ultraviolet illumination on NaCl-induced atmospheric corrosion of pure copper were studied in this paper.It was found that the atmospheric corrosion rate of pure copper can be significantly accelerated by UV illumination.While,the corrosion morphology of copper under UV radiation changed but the type of corrosion products did not change.Under the white light illumination,the corroded pure copper showed a negatively shifted potential which is resulted from the photoelectrochemical properties of the corrosion products.Generally,the negatively shifted potential is companied with protection of the metal,but in this case it accelerated copper corrosion.In order to study this process,scraping corrosion products and coated it on the surface of FTO glass to fabricate thin film photoelectrode,which was used to research the photoelectrochemical effect of corrosion products.FTO thin film photoelectrode under white light induced a positively shifted potential.Coupling thin film photoelectrode and clean copper electrode,it was found that under the white light illumination induced the potential positively shift of this coupled system.To measure the current between corrosion products FTO thin film electrode and the clean copper electrode,electrons flew from the copper electrode into the FTO film photoelectrode.It was indicated that the photoelectrochemical reactions of the corrosion products occurred on FTO glass surface were different from those on the copper's surface.On the copper's surface,ultraviolet radiation induced corrosion products' photo-electrochemical effect to produce electrons and holes,electrons flew to and reacted with the solution,meanwhile photoinduced holes reacted with the copper directly.Since the reaction rate of holes is faster than that of the electrons,which causes electrons accumulated and produce negatively shifted potential of corroded copper with the accelerated corrosion.While,on the FTO glass surface,photogenerated holes couldn't react with FTO glass,but the electrons reacted with solution,leading to the accumulation of the photo-generated holes on the surface of electrode under white light radiation and resulted in produced positive shift of potential.The photoinduced current which flew from the metal electrode to corrosion products coated FTO thin film electrode also illustrates the process of the accelerated corrosion under light illumination.At the end of this dissertation,the influence of UV illumination on the atmospheric corrosion with various semiconductor materials coated copper was also explored.The results showed that the coated TiO₂ can slow down the atmospheric corrosion of pure copper in the actual exposure.The possible reason is caused by the photoelectrochemical process of TiO₂,while the process and mechanism need to be further studied in the future.