So you're asking a question that for a proper answer requires some knowledge of Chemical Engineering principles including chemical re/dox processes and thermodynamics. Frankly this is all unnecessary to know for basic razor storage.

Essentially relative humidity is the Partial Pressure of Water present divided by The vapor of Water at the reference temperature. That means humidity is Temperature and pressure dependent. So when two gasses are mixed (in this case Air is treated as 1 gas and Water vapor is the other) then fraction of the total pressure that is provided by Water is the partial pressure of water. The vapor pressure of water is the pressure at whatever temperature your system is at that causes Water to reach it's Bubble point aka to become a vapor. So generally speaking the oxidation of metal caused by Humidity is actually going to be Temperature dependent of the space the razor is occupying. Volume of your system will also play a role here as the Pressure will also vary with Volume (and Temp for that matter) which can be seen looking at a Phase Diagram or P-V diagram for Water.

None of this is important however for the basic storage needs. The real factor here that is going to be important is Volume. Without going into too much detail the smaller a space that you keep the razor in then the more likely the water vapor in the air (the humidity for our purposes) will reach it's Wet region (the point at which water is in a vapor/liquid mix) or it's Liquid phase and will speed up the oxidation process. This is why people should be careful when storing razors in their original boxes as it will "trap" moisture or more accurately it will not allow that moisture to reach it's gaseous phase where it will be far less likely to cause oxidation. When in the gas state the molecules are moving much faster and far more spread out.


So I digress. The important thing here is if you want to prevent oxidation then you can take the following steps:

1) the most obvious step is to properly dry the razor after use.


2) Store the razor in an Open environment rather than a closed space.


3) If you're storing it in a closed space then monitor the temperature. The lower your Volume then the lower temperature that water will go from a Gas to a liquid.


4) Use a thin layer of oil to prevent water from contacting the blade. This is mostly important again in small area where the water will not evaporate so in the Hinge point is especially important.