based on standard reduction potentials which metals would

i) inhibit rusting
ii)promote rusting

My general statement is:
> If the reduction potential is higher it will inhibits rusting and if it is lower it will promote rusting

But im not sure because it doesn't make sense with Mg

For a given reduction potential table, electron flow is from the more negative E-value to the more positive E-value. This would imply metals with a more negative E-value would undergo oxidation and the more positive E-value reduction. So, considering Zn => Zn^+2 + 2e (E = -0.76v) would be the reducing agent for Fe^+3 + 3e => Fe (E = -0.04v). As the Zn is the anode (undergoing oxidation) and the cathode (undergoing reduction) would indicate E-values that are more negative relative to Fe reduction potential (assuming you are referring to Ferric Oxide rust) would inhibit rusting. Such is referred to as 'Cathodic Protection'; that is, one is trying to protect the metal at the cathode by connecting with a more negative E-value metal as the anode. The anode will disintegrate before the metal at the cathode.

Your general statement is correct: if the reduction potential is higher, it means the metal is more likely to undergo reduction and will thus inhibit rusting. Conversely, if the reduction potential is lower, the metal is less likely to undergo reduction and can promote rusting.

However, there are a few exceptions to this general statement, and magnesium (Mg) is one of them. Although magnesium has a high reduction potential, it does not inhibit rusting. This is because magnesium has a tendency to react with oxygen and water, forming a protective layer of magnesium oxide (MgO) on its surface. This layer acts as a barrier, preventing further corrosion.

To determine which metals inhibit or promote rusting based on their reduction potentials, you can refer to a table of standard reduction potentials. In general, metals with higher reduction potentials than iron (Fe) will inhibit rusting, while metals with lower reduction potentials will promote rusting.

For example, metals like gold (Au) and platinum (Pt) have higher reduction potentials than iron and will therefore inhibit rusting. On the other hand, metals like zinc (Zn) and aluminum (Al) have lower reduction potentials than iron and can promote rusting.

It is important to note that other factors, such as the presence of other ions or impurities in the environment, can also influence the rusting process. The reduction potential is just one factor to consider when determining which metals inhibit or promote rusting.