Quicklime is one word. It is calcium oxide (CaO) and will absorb moisture from the air to become calcium hydroxide, which is considered a strong base as per definition but is barely soluble with water. I don't know how long it would take for that much to fully convert. It makes an excellent soil "sweetener" for acidic soils.
It will eventually rust, but how fast it will rust depends on a lot of other factors. How much exchange of air there is between the luggage compartment and the air outside it. how humid s the air outside, Is the luggage compartment heated or cold, ...
example: A common situation is that there are air passages between the luggage compartment and the passenger compartment, people produce a lot of water vapor and heat, even when they are just sitting so this would lead to condensation in a colder luggage compartment, moisture makes things rust faster. If the showel also have traces of salt on it (from shoveling snow) it will rust even faster. Then again sun shining on the luggager compartmenent will quickly heat it op, making for less condensation and dryer air. Lots of factors all balancing against eachother :-))
Element 99 