aNote values in (italics) represent deaerated seawater conditions.

aNote values in (italics) represent deaerated seawater conditions.

1. The difference between the corrosion potentials of the uncoupled metals

2. The conductivity of the solution

3. Anode/cathode area ratio

4. Distance between the couple.

In general, a large difference in corrosion potentials, a large cathode/anode ratio, and small distance between the metals will give rise to the greatest corrosion rate.

This assessment of susceptibility assumes that the corresponding cathodic reactions are not influenced by polarization (overpotential) effects. For example, if we consider the galvanic couples of Mg-Pt and Mg-Hg, the rate of corrosion of Mg should be similar for each couple because E for Mg = -1.6 V (vs. SHE), and both Pt and Hg « 0.2 V. However, the rate of corrosion for the Mg-Hg couple is extremely low because the hydrogen evolution overpotential on the Hg surface is 8 orders of magnitude lower than that at the Pt surface.

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