The change from shiny to dull is called tarnishing. close tarnishingThe reaction of a metal with oxygen with air in which the surface of the metal changes from shiny to dull.
R.T. Skodje, "Resonances in Bimolecular Chemical Reactions", Advances in Quantum Chemistry, 63, 119-164 (2012). R. T. Skodje, D. Skouteris, D. E. Manolopoulos, S.-H ...