How does water make metals oxidize?

zbeckabee

Air-free water has little effect upon iron metal. However, iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting and is familiar to any car owner. http://www.webelements.com/webelements/elements/text/Fe/chem.html Apr 24 06, 5:45 PM

xfacilitatorx

When steel contacts water, an electrochemical process starts. On the surface of the metal, iron is oxidised to iron(II): Fe → Fe2+ + 2e- The electrons released travel to the edges of the water droplet, where there is plenty of dissolved oxygen. They reduce the oxygen and water to hydroxide ions: 4e- + O2 + 2H2O → 4OH- The hydroxide ions react with the iron(II) ions and more dissolved oxygen to form iron oxide. The hydration is variable, however in its most general form: Fe2+ + 2OH- → Fe(OH)2 4Fe(OH)2 + O2 → 2(Fe2O3.xH2O) + 2H2O Hence, rust is hydrated iron(III) oxide. Corrosion tends to progress faster in seawater than fresh water due to higher concentration of sodium chloride ions, making the solution more conductive. Rusting is also accelerated in the presence of acids, but inhibited by alkalis. Rust can often be removed through electrolysis, however the base metal object can not be restored through this method. http://www.reference.com/browse/wiki/Rust http://www.reference.com/browse/wiki/Rust Apr 24 06, 9:54 PM