Fe is oxidized to fe2 fe o2 h2o fe2 2oh feoh2

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Unformatted text preview: rosion Electrochemical Corrosion The oxida9on of iron (rus9ng) occurs in two steps. Fe is oxidized to Fe2+ Fe + ½O2 +H2O Fe2+ + 2OH- Fe(OH)2 Then, Fe2+ is oxidized to Fe3+ Fe2+ 2Fe(OH)2 + ½O2 +H2O 2Fe(OH) Fe3+ This process is due to dissolved oxygen in the water and concentra;on differences. Electrochemical Corrosion Electrochemical Corrosion Electrochemical corrosion - Corrosion produced by the development of a current in an electrochemical cell that removes ions from the material. Electrochemical cell - A cell in which electrons and ions can flow by separate paths between two materials, producing a current which, in turn, leads to corrosion or pla9ng. Oxida6on reac6on - The anode reac9on by which electrons are given up to the electrochemical cell. Reduc6on reac6on - The cathode reac9on by which electrons are accepted from the electrochemical cell. Corrosion of Ceramics Electrochemical Corrosion •  Ceramics are generally resistant to corrosion. •  When corrosion does occur in ceramics, it is by simple chemical dissolu9on. Corrosion of Polymers Electrochemical Corrosion •  Swelling and Dissolu9on •  Bond Rupture (Chemical and Radia9on) •  Thermal Breakdown (also bond rupture) Fuel pipe connector Lignin photo- degrada9on Ozone cracking in natural rubber Chlorine degrada9on of acetal resin...
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