Reproportionation of cooper(I) in the chloride medium can be considered as a particular kin d of metal corrosion also called spontaneousmetal dissolution. It should be emphasized that such a corrosion process occurs when copper is immersed into an electrolyte containing its own ion of higher oxidation state Cu(II) which acts as the oxidant. Corrosion process of metal are of great importance in the environment. It is essential that students become more aware of these topics. However easy to perform demonstrations are rarely describe in literature. In this article we report an easy and attractive set of laboratory experiments illustrating the dramatic change in the redox and consequently corrosion properties of cooper. The experiment was designed to show spontaneous dissolution of copper metal in solution. For comparison an analogus experiment should be performed in a solution containing dilute H2SO4 as the background electrolyte. The SO42-ion is not able to complex cooper ion.In this solution the redox properties of the system under study are comparable to those charasteristic of the standart solution.