Harmful
its harmful because when metal goes rusty it looses it power and then eventually the car will fall apart.
No
That depends on what effect is desired; If you like to breathe, it is a useful gas; If you prefer that your car (or whatever) not be rusty (oxidized), then it is a harmful gas.
yes it does
Lubricating them with products such as WD-40. It's something which needs to be done regularly.
It rusts
It may be. A good cook would not use any rusty tool
Rusty Nail or Rusty Spike.
It rusts
Most likely, the dent causes a 'peeled off' plating thus resulting in a rusty surface. Rust is harmful!
There are a few reasons why your alternator might keep going bad such as rusty latches under the car. You may also have leaks, dents, or parts that need to be replaced on the vehicle that are effecting your alternator.