Thanks, Jack, for the info. After some further reading on the subject, I found that black pipe is commonly used for gas connections and that it is normal (even desirable) for it to oxidize. According to what I read, it forms ferrous oxide rust, as opposed to the ferric oxide rust that forms on galvanized pipe. The ferrous oxide layer serves as a protective surface that inhibits further oxidation. So, as you say, my concern about the rusted gas manifold appears to have been unjustified. It was just a bit of a shock to see so much rust forming on a component of a new motor home.