Effect Of Visible Light Illumination On The Atmospheric Corrosion Of Copper

Metallic materials serving in the atmospheric environments are usually exposed to solar light illumination,which affects the corrosion of metallic materials a lot and cannot be overlooked.Visible light accounts for a large proportion of the entire spectrum of solar light arriving to earth surface that gives rise to specific significance of investigating the corrosion of metallic materials under visible light illumination.In this paper,atmospheric corrosion of copper was studied under the visible light illumination,aiming at revealing the influence of visible light illumination on the corrosion behaviors and processes of copper,simultaneously researching the impact of different pickling solutions on mass losses of copper.All of the above would provide some supplementary to the theory of copper atmospheric corrosion.The main results are presented as follows:(1)Influence of visible light illumination on the atmospheric corrosion behavior of copper.The composition of the corrosion products did not vary over visible light illumination compared to that exposed in the dark,both in which the cuprite remained the main corrosion products phase.Nonetheless,visible light illumination affects the corrosion morphologies of copper exposed under atmospheric environments by forming more compact product layers than those formed in the dark.In addition,the atmospheric corrosion rates of copper exposed under visible light illumination are approximate 2 to3 times that obtained in the dark,demonstrating a promotion mechanism of copper corrosion under visible light illumination.(2)The electrochemical/photoelectrochemical properties of the corroded samples and corrosion products of copper were studied in this paper.The results suggest that the corrosion product layers on copper samples could alleviate the corrosion due to the compact cuprite layer whose protection effect would be promoted with increasing exposing time despite the visible light illumination.Furthermore,the results of photocurrent and photovoltage tests validate that the corrosion could be promoted due to the n-type semiconductor properties of corrosion products,while the photoinduced holes would be generated under the visible light illumination and oxidize copper substrate to copper ions for products generation.(3)Effect of different pickling solutions for mass loss determination of copper.According to the comparative studies,it is found that the weight losses of copper samples obtained after the treatments with three kinds of pickling solutions recommended by the international standard are significantly different due to the disproportionation reaction of Cu~+.The mass losses obtained by pickling the copper samples with hydrochloric acid are quite close to the true value because the chloride ions in the hydrochloric acid solution would complex with the cuprous ions to prevent the disproportionation reaction of cuprous ions during the pickling process.In view of the convenience of the operation and the accuracy,the microgravimetry method,i.e.,treating samples by the undeoxygenated hydrochloric acid solution is recommended to determine the mass loss of copper.