Brass & Iron

I had to change a shut off on my water heater from a wrench type black pipe shut off to a simple half turn shut. The shut off is brass. Are there any known issues with brass to black pipe (is that iron) connections or metals?

Also I used TFE paste. Is that cool with gas (brass & black pipe)?

Thx

A brass valve will be fine IF it is rated for gas. Same for the pipe dope...if it is rated for use with gas, it should be fine.