Sometimes a chip will cause the coil casing to leak.
On the other hand some coils have electronics "chips" in them and without the chips the things would never work.
I couldn't resist the lame "chip" pun, mostly because it's nice to give out a bit of undisclosed info now and then.
A product called "FlexableSeal" is available in white, grey, brown, clear, etc (about $5 a tube) and it is the best water sealant on the planet. You can find it in only a (few) hardware stores, but nearly EVERY dedicated (roofers) supply in America has it. It's the best sealant available for metal roofs, and it is SUPER!
LL