A few days ago, I noticed that there is some water dripping from the
gas pipe at the place the pipe entering our basement.

Then I found out that the pipe entrance hole is not sealed (we bought
this house just a year a ago). So I guess the water was because the
pipe is cold enough to cause the more humid air in the basement to
condense.

I tried sealing up the hole but it doesn't help.

My question:
1) Why sealing it up doesn't help. Basement is around 57F. Am I missing
something?
2) How do I solve the problem? Is there some kind of material I put on
to at least not let the pipe corrode. I think the pipe is black iron.