I was cleaning the inside of my car yesterday and had the seat extension pulled out on the passenger side and noticed a small amount of surface rust on the metal piece there. Does anyone else have this issue?

 

I think every car I have ever looked at the rails had slight rust on them. IMHO its very common.

 

Did you buy the car used? Rust on interior metal parts can be in indication of previous flood damage. Not always in every circumstance, but you can find out by checking other areas inside the car that shouldn't have rust so see if they do or not.

 

It's uncoated steel I'm sure like most other cars. Sitting in a humid environment will do that.
I've had it happen on cars I have owned brand new

 

I bought it used from Chicago, it is absolutely perfect inside and out and still smells brand new. It is just that tiny spot on the seat, but not a spec of rust anywhere else besides the brake calipers that typically happens overtime.