What is the rust on my lawnmower handle?

When I had a real car with real chromed bumpers, if there was rust it usually buffed off with rubbing compound.
Now that I have no room for the lawn mower in the house, and the plastic cover came off, there are some rust spots on the handle.
But these come off with my finger or fingernail, and the chrome seems perfect underneath. Not even a little hole visible to my naked eye.
Is the chrome on the handlebar being damaged or not?
I've seen other handlebars with the chrome flaking off, and I figure it starts with little rust spots, but if the steel underneath the chrome is rusting, how come when I rub off the rust, I see the chrome, and not the steel? Same question about my car's bumpers?
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