What is the electrode reaction that occurs at the anode when steel undergoes oxygen-induced corrosion?
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What is the electrode reaction that occurs at the anode when steel undergoes oxygen-induced corrosion? Thank you
Anodic reaction: Fe – 2e⁻. Cathodic reaction: In acidic solution: O₂ + 4H⁺ + 4e⁻ → 2H₂O; in alkaline solution: O₂ + 2H₂O + 4e⁻ → 2H₂O
I remember that the corrosion of steel in air that is close to neutral conditions is called oxygen absorption corrosion: Anode (Fe): Fe – 2e = Fe2+; Cathode (C): 2H2O + O2 + 4e = 4OH-. In solutions with a higher acidity, corrosion results in the release of hydrogen gas, and this is known as hydrogen evolution corrosion: Anode (Fe): Iron is oxidized, Fe – 2e = Fe2+; Cathode (C): H+ ions in the solution are reduced, 2H+ + 2e = H2. Both are forms of self-corrosion in galvanic cells. This post was last edited by zolf on 2008-11-10 10:03]
In neutral, alkaline, and weakly acidic solutions, the hydrogen ion concentration is low, resulting in a more negative potential for the hydrogen evolution reaction; whereas the oxygen reduction reaction can occur at a much higher potential. Under these conditions, oxygen depolarization gains an advantage, leading to oxygen corrosion. In weakly acidic solutions: O2 + 4H+ + 4e → 2H2O. In neutral and alkaline solutions: O2 + 2H2O + 4e → 4OH--
http://bk.baidu.com/view/979819.htm Oxygen-induced corrosion: It is a type of electrochemical corrosion that occurs when oxygen from the air dissolves into the water film on the surface of metals in solutions that are either very weakly acidic or neutral. For example, the corrosion of steel in humid air that is close to neutral is a case of oxygen-induced corrosion. The electrode reactions for this process are as follows: Anode (Fe): 2Fe – 4e⁻ = 2Fe²⁺; Cathode (C): 2H₂O + O₂ + 4e⁻ = 4OH⁻. Electrochemical corrosion of metals such as steel is primarily of the oxygen-induced corrosion type. Necessary conditions for oxygen-induced corrosion: Corrosion in which the reduction of oxygen serves as the cathodic process is known as oxygen reduction corrosion, or oxygen-induced corrosion. A necessary condition for oxygen absorption corrosion is that the potential of the metal is lower than the potential of the oxygen reduction reaction: EM