Metal corrodes. However, there are things we can do to prevent or mitigate the effects.
Let's talk about frames first. Aluminum does not rust. Although bare steel rusts, painted steel is quite protected from the elements. We have seen an eighty year-old frame that was in serviceable condition because the paint protected it form the effects of the salty beach air where it was kept.
Conclusion, rust and corrosion should not be factor in choosing frame material.
Chrome. There are different ways to apply a chrome look to parts. Some are more expensive than others. You may see expensive, high-end parts on classic automobiles that withstand the elements. On bikes, the cost is not worth it. The chrome on most bikes will last just fine if kept inside and away from salt. However, bicycle chrome can degrade rather quickly in salty conditions where the bike is left outside and the salt is not rinsed off after rides. If you live in a salty area, please rinse the bike off with a hose after a ride.
The best bet for fully protecting a bike is to get one that has everything painted: frame, wheels, and the parts. The Around The Block is a good example of a bike that's fully painted.
Even on a bike like this, the gears and chain are still exposed. On competition bikes, special alloys are used to prevent corrosion. On hybrid bikes and beach cruisers like ours, the chain and gears will eventually rust if stored in the weather or not rinsed after rides. It is a very good idea to keep these parts properly lubricated with a good bicycle chain oil. Oil the chain once a month by putting a drop on each link (done rapidly by squeezing a constant stream while moving the bottle quickly along the length of the chain). Then make sure to wipe off the excess oil so as not to attract grime. The oil only needs to be between the plates and rings of the chain. Keep a thin sheen of oil on the gears as well.