Effects of the Environmental Pressure in the Corrosion Potential of the Copper that Will Be Used as Container of High Level Radioactive Waste

Abstract

ABSTRACTThe SKB project of Sweden has considered copper as the most appropriate metal to be used as container for high activity radioactive waste. However, it is still necessary to carry out some studies that can assure that their chemical, physical, mechanical properties, etc. do not loose stability in a period so long as 100.000 years.In this work we show using anodic polarization, the corrosion potential (Ecorr) behaviour in different pressurized environment. The copper surface was characterized using optical microscopy. The electrochemical cell was mounted in a high pressure chamber that allowed to work up to 40 atm. The electrolyte solution simulates the deep groundwater, being the composition reported in literature [1].The experimental results in solutions without bentonite show only slightly changes of the corrosion potential to cathodic values. At pressures of 40 atm, products of corrosion are observed, covering micropitting, that can be induced because of a bigger interaction metal/ ion at these pressures.In the other case, bentonite presence produces beneficial effects in the resistance of the copper corrosion, since it is observed that the corrosion potential is displaced to more anodics values. This effects could be explained due to that this clay is able to retain ions that are aggressives for copper, such as chloride, sulphide, etc., and it liberates others that don't produce deterioration, such as sodium, that is in concordance with others authors[15].