Give brief explanations (3 or 4 lines) for the following: a). Silver is oxidized by nitric acid, but gold is resistant to oxidation by nitric acid. b). Aluminium does not corrode readily in moist air, but iron does. c). You should not replace a section of galvanized iron pipe with copper pipe when doing plumbing repairs. d
Corrosion, in electrochemistry, is the gradual destruction of an electrode caused by an electrochemical process. This is commonly seen in the form of rust on iron. Other examples include the black corrosion found on silver and the red corrosion found on brass. The main cause of this corrosion is the electrochemical oxidation due to the presence of strong oxidants such as oxygen, to form oxides of the respective metals. In this corrosion process all the useful properties of the metal or material will slowly degrade, such as its electrical conductivity, strength and appearance. The corrosion of iron is done in the following electrochemical manner: 4Fe2+ +O2 --> 4 Fe3+ +2O2- The product of this oxidation reaction can then react with water to form Fe(OH)_3, which can dry up in the absence of any water to form Fe_2_O_3, which is the distinctively red compound in rust. Thus, understanding the corrosion process may help devise ways to prevent material degradation.