ChemistryPhysical ChemistryElectrochemistryCorrosionTopCorrosionIt’s not necessary that all redox reactions are part of energy change. You can notice many reactions around you which involve a negligible amount of energy or occurs without change in energy. For example, Silver metal is oxidized when it comes in contact in the atmosphere oxygen or hydrogen disulphide.
4Ag(s)+2H2S(g)+O2(g)→2Ag2S(s)+2H2O(g)
The film of sulphide which collects on the metal surface acts as a protective layer for further oxidation of metal surfaces. The tarnishing of silver is just one example of a broad class of oxidation-reduction reactions that fall under the general heading of corrosion. The rust of the metals because of corrosion of the surface is an example of the oxidation reaction.
