York furnace heat exchanger rusting normal ?

[Ratdog]

Hi folks,

I have a York furnace model G-UA060S21B (Diamond 90) gas furnace about 9 years old that has a small amount of rust on the 2 connection mounting flanges. Is this something that would be typical over the life of the furnace? I wish I could be more descriptive of where exactly they attach, but I have been unable to find an exploded diagram.

Thanks,
Richard