Dr. P. Lucas U of A MSE 110 Corrosion•Corrosion is the deterioration of metals by spontaneous redoxreactions.•Corrosion in the environment is due to the combined effect of water and oxygen.•Most metal have Eo<1.23 hence the thermodynamically stable equilibrium state of most metals in nature is in the oxidized form.•Corrosion can be naturally slowed down by the lack of H2O or by formation of a protective layer such as Zn2(OH)2CO3 or Al2O3.•Fe oxidizes in two steps, first forming Fe(OH)2followed by Fe(OH)3. Thisrust peals off and re-expose the metal to further oxidation. •At the anodic site Fe is oxidized andgoes in solution as Fe2+/3+and at the cathodicsite H2O/O2are reduced to OH-and the rust is deposited.•Asacrificial anode is a metals with low redoxpotential connected to Fe which is oxidized in place of the Fe part.SUMMARY FROM LAST CLASSEo(O2/H2O)= 1.23 VO2+ 4 H++ 4e-Æ2 H2OEo(O2/OH-)= 0.40 VO2+ 2 H2O + 4e-Æ4 OH-
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Dr. P. Lucas U of A MSE 110 Batteries:•There is two general class of batteries: rechargeable and non-rechargeable.ELECTROCHEMICAL DEVICES•Primary batteries:•The redoxreaction taking place in a primary battery is non-reversible, the reactant can not be regenerated by applying a potential to drive the reverse reaction.•Alkaline batteries are a typical example of primary battery.Zn + 2 MnO2ÆZnO + Mn2O3•This reaction can not be reversed, hence the alkaline battery is non-rechargeable