I'd base the course of action on whether that galvanized pipe is
obstructed. Does the sink drain rapidly ? Can you get a wire hanger
thru there ?

If it seems healthy I'd leave it alone. If it's a problem right now,
that is, water doesn't drain, it's probably because the galv. pipe is
corroded down to where only a trickle of water can pass.

I'm pretty handy but I'd call a plumber cause of the junction of that
pipe with what probably is an iron stack, assuming it's an old house.