Question

How does the concentration of Oxygen affect the rate of corrosion of steel in seawater and on land?

Answer 1

Generally, it is required in stoichiometric ratios with water. Relative humidity affects corrosion more than oxygen, but both water and oxygen are usually plentiful.

Explanation:

Seawater is particularly corrosive because it also contains chlorides. Oxygen availability underwater may reduce the rate compared to a wet environment on land.

Some excellent sources with calculations and other considerations for this problem are here:
http://www.steelconstruction.info/Corrosion_of_structural_steel

https://www.galvanizeit.org/corrosion/corrosion-process/corrosion-rate